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Port Engine lost power - Need some help please

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Need some help figuring out what is going on with my Port engine

This weekend finally had good weather forecasted so we went on a 30 Mile trip and spend a few days in one of our favorite spot. We cruised at and average of 26 MPH for about an hour each way, it was uneventful on the way there. On the way back today, went well at the same average speed as on the way to the spot, when we got into the bay and the water was nice and smooth and only about 5 miles from the marina, I decided to open it up just to have a few minutes at WOT. We’re headed into the wind at 40MPH for a few minutes, when out of nowhere the boat started slowing down very fast, and I just pulled throttles to neutral to figure out what happened. The temperature on the port engine went up slightly, so I open the engine hatch, there were no obvious signs of anything abnormal…no smoke, oil or anything like that byt the time I returned to the gauges the temp was back to normal. Got the Laser Temp gun and did not notice any hotspots. Engines were idling, the port engine seemed to be vibrating a bit more than usual.
While the hatch was open I increased throttle in gear while looking at the engine, it sounded like it was misfiring and would vibrate/shake to where you could feel it through the boat and definitely a lot less power than usual. I used mostly the Starboard engine to bring us in – with just slight forward throttle on the port engine. As we got to the marina, the Port engine sounded better but still not like before. I didn’t want to run it anymore than necessary before figuring out what was going on.
Here is some background on the engine. Currently 297 Hrs on it
New Cool Fuel filters within the last 2 hrs
New manifold and risers within the last 5 hrs -- so brand new
Also replaced spark plugs when I did the manifolds - ACDelco 41-993 plugs
New Thermostat, water impellor – within the last 10 hrs
New oil and filter at beginning of season – within the last 25-30 hrs
Fuel is fresh, we have been using it a bit this summer, when I replace the Fuel filters I did not see any water or debris in the fuel cup
The last 3 times we went out, the port engine would not start if was still hot, unless I gave it throttle in neutral as I turned the key, this is why I changed the filters in the Cool Fuel system.
But today after we pulled the boat out of the water it started right up, and faster than before as we flushed the motor. The water was nice and hot from the exhaust, ran it for about 10 minutes with slight throttle. Turned it of for 10 minutes, and hooked the water hose again and cranked right up. In the past I would hold the key in the on position for about 2-3 seconds before it fired up. Now as soon as you turn the key it starts. The Starboard engine always started a bit faster and today while we flushed it, it was no different… but the port engine starts up faster…I’m puzzled.
I will be staring it on the hose tomorrow morning to see what it sounds like and how it starts when cold. But before I do that, I was wondering if anyone has any advice/suggestions on what I should do to check this problem out.
Thank you for your help.

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Old weak batteries ? Date on the batteries ?  Enough water in every cell of batteries.  Cranking speed of each battery and or starter motor ?  

The faster starting after a hot restart points to weak batteries with possible sulfate build up.

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On ‎9‎/‎12‎/‎2018 at 6:38 PM, 330Signature said:

Have you scanned the smart craft for codes? Have you checked the color of the oil?

The shops around here are all booked up for a few weeks to even take time to run a diagnostics  -- Oil still looks honey color - only 35 hrs on it no evidence of water and smells normal as far as I can tell.

 

On ‎9‎/‎13‎/‎2018 at 5:56 AM, cyclops2 said:

Old weak batteries ? Date on the batteries ?  Enough water in every cell of batteries.  Cranking speed of each battery and or starter motor ?  

The faster starting after a hot restart points to weak batteries with possible sulfate build up.

Batteries are fine, water level is good, and one battery (house) was replaced in the last few months. Always on charger when out of the water

Here is what I have done so far. Replaced distributor cap and rotor -- not sure why, but the old cap said it was marine certified but the posts were made of aluminum and all the posts including the center were covered in a white corrosion. The new cap has brass posts.

Noticed that the port side of the motor was not getting hot like the starboard side 9by just placing my hands over the exhaust manifolds, matter of fact is was just barely warm where as the starboard side I couldn't keep my hand on it- removed all the spark plugs - the port side had one plug missing the center electrode the others were all black, same thing on the starboard side, but there was some of the center electrode remaining on the one that was broke.

Read on another post that it could be the Crankshaft Positioning Sensor (CPS) -- good thing having 2 engines, swapped them out and still no difference.
 
Got new plugs ACDelco 41-993 and gapped them to 0.060 per the manual -- post side does not seam to be firing, does not get hot...ran out of time to remove plugs and check condition.
Tomorrow plan on checking fuel pressure. Also found out from the parts department that Mercury advises to use NGK IT4A15 plugs that are pre-gapped at 0.060, so ordered enough for both engines (parts dept. here in town wanted 125 deer for each set of 8 - got both sets online for that same cost)

anyone else have some more suggestions???
Thank you for helping out

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Sticking open thermostat will BLACKEN PLUGS VERY FAST !!   Been there many times.

Cheap job if not done already

You are boating a HUGE BLACK CLOUD !!    Get some luck.

Have all cylinders compression checked.  The readings are taken with the sparkplugs removed.

Always ground the H V coil lead to prevent the super high coil voltage from arching in the coil. It happens. Nasty  of a DIY problem to prove.

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I believe the port engine is the one where the new thermostat was causing overheating?  Also, please post the full model and year of the engines. 

11 hours ago, Dozer said:

removed all the spark plugs - the port side had one plug missing the center electrode the others were all black, same thing on the starboard side, but there was some of the center electrode remaining on the one that was broke.

So, on both sides of the port engine there was a missing/broke center electrode on a spark plug?  Not trying to call you out, but could be two bad new plugs (manufacturing defect or damage from installation (dropped, over torqued, etc.).  If there was interference in these two cylinders, which is unlikely, the engine would have made a pretty decent noise and you'd of heard it.  What's concerning is where did the broke pieces go...  A compression check is a great idea, like wise so is changing the oil/oil filter (again) and replacing all of the plugs (being sure to not drop or over torque, and that the heat range and gap are correct for the engine).  The fact moving the crankshaft position sensor didn't change the result, points to the plugs at this time (this could change as more information is developed).  Could also be a bad reluctor wheel, but two bad plugs will cause power problems and known good plugs are needed before further troubleshooting can occur. 

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Curt
You're correct, after changing the manifolds, the engine was still overheating and it was due to the faulty (new) thermostat. Although I was careful in making sure as soon as it go hot to throttle back and make sure it cooled off...so I don't think it got that hot to cause any serious damage (hope not).

Yes, one CENTER electrode (porcelain and wire) were missing on one cylinder  on each side. All the plugs are black and sooty. Last night I replaced the plugs and ran the engine for a few minutes, so I have not removed them to inspect yet. As for defects, could very well be...not sure, I gapped the old ones and don't recall dropping them. I used a torque setting of 11lbs to set the plugs. Also the engines ran fine for 25 miles one way and two days later another 25 miles back to the marina, than when I had it WOT that is when I lost power.

As for the pieces of the plugs... not sure what happened, I inserted a bore camera (it's a cheap one, not the best picture) but I could not see any debris. I assume they didn't brake up all at once, and when it did the small pieces (probably the size of sand grain) were expelled through the exhaust...I hope.

As for the Cylinder testing, I have never done one, but it says the engine should be at operating temp... right now the port side of the engine is not warming up, and if it did, it would be a pain to remove the plugs when the manifolds are hot. I can barely get my hands on the plugs and wire boots when it's cold. Can you get a decent pressure test with a cold engine?

How can a reluctor wheel go bad?

I just returned from the parts store with a fuel pressure gauge kit to see if fuel pressure is an issue. I'll report back with the findings
As for the engines they are  2006 Mercruiser MPI 5.0 w/ Bravo III -- serial # OW614502  and   OW614504

Figures, this is the first nice and dry weekend we have had in while....and instead of being on the water...here I am  :( 

Thanks Curt for the help

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Just tested fuel pressure. Ignition ON = 40psi    engine running at idle the needle flutters rapidly between 38-42 psi
Confirmed the dame results on Starboard engine (the one running normal)

For kicks I swapped the  Idle Control valve/sensor -- no change
Air filter is clean

Removed one spark plug on Port side -- the one that does not get hot as the engine runs, it look clean -- but only has a few minutes of run time on it.

Any suggestions????

THanks

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Check the plugs after a on plane run of about 15 minutes.

Sooty plugs ?   Over rich condition on all of them ?    HUMMMMM  Got it !!  The engine automatic choke / COMPUTER & SENSOR is stuck on full rich mode.  Maybe from that COLD engine running condition Get the engine heat corrected first.......... Then the sooty plugs & rough running will stop.

My Evinrude 30 hp O B engine is rough at low and change of speeds. If it idles too long while trolling........ It simply COOLS OFF to much. So I tease it up to plane speed. Then a stop & slammed to WOT is a great shot instantly.

I have changed stats enough times. 

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4 hours ago, Dozer said:

As for the Cylinder testing, I have never done one, but it says the engine should be at operating temp... right now the port side of the engine is not warming up, and if it did, it would be a pain to remove the plugs when the manifolds are hot. I can barely get my hands on the plugs and wire boots when it's cold. Can you get a decent pressure test with a cold engine?

This is loaded question.  In my opinion, yes.  Others will disagree.  It's kind of like some prefer Mercury, while others prefer Volvo.  In reality, both are right.  In general, we're looking for values in the range of 125 to 160, with no more than a 25% (some say 10%) difference between the max. and min.

4 hours ago, Dozer said:

How can a reluctor wheel go bad?

The pick ups are magnets or slots. Sometimes they shift, get hit, etc. I'm not saying this is the issue, and I don't suggest replacing it at this time. More troubleshooting is required. 

2 hours ago, Dozer said:

Just tested fuel pressure. Ignition ON = 40psi    engine running at idle the needle flutters rapidly between 38-42 psi

I don't know the Mercury spec.  The 5.0 Volvo Penta spec. is 50 to 60 PSI, +/- 2. 

Flutter is normal. 

2 hours ago, Dozer said:

Removed one spark plug on Port side -- the one that does not get hot as the engine runs, it look clean -- but only has a few minutes of run time on it.

Okay.  The two that were damaged, did they appear hit (e.g. impact damage), broken or "worn away"?  11 ft.-lbs. is proper torque.

2 hours ago, Dozer said:

Any suggestions????

(a)  Your ECM likely has an engine rev. limiter that drops-out 4 cylinders when coolant temperature is less 140-F.  Likewise, there's a protect mode that reduces/limits power or kills the engine when certain parameters are exceeded, e.g. high temperature, low oil pressure, etc.  What you described in an earlier posts sounds like it could be either of these modes kicking in.  What to fix lies in determining which mode is kicking in.  Scanning for codes and a live scan are the next steps, unless there's an audible alarm that can be described.  Anything other is remove and replace, remove and replace, remove and replace.  (Testing the ECT and the other sensors that trigger protect mode is possible.  It is much more time consuming compared to a scan tool though; many hours vs. a few minutes.  Most sensors operate at 5 volts.  An open circuit on either the signal or return wire sets a high voltage fault, which is interpreted by the ECM as needing to reduce power, or depending on the sensor, kill the engine.  There's some variation to the preceding, but in general this is how it works.) 

(b)  Another possibility, particularly given manifold replacement and so forth, is chaffed wiring.   

(c)  How does the engine sound with new plugs.  Normal, or is it missing or power limited?

 

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If it can drop 4 cylinders when below 140 F.  How can you run the boat until 140 F is reached ?   What is the warmed up temperature  ? 

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Do your spark plugs have a loose sealing ring to be compressed ?   Or just a NO SEALING washer type ? 

The sealing washer types can require some what more than 11 foot pounds of seating torque.  I was sooting up new NGK on the O B . Called NGK. Told me to feel the washer seating. THEN CONTINUE crushing it UNTILL A REAL RESISTANCE WAS FELT................  ONLY CHANGE PLUGS ON A COLD ENGINE. Especially Aluminum threads.

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A compression test is normally done stone cold. For many reasons. As Curt mentioned. The key finding is ALMOST IDENTICAL readings on all of them. Great !!

But if you get 2 side by cylinders almost EQUAL.  Both DIFFERENT FROM the rest.  Trouble..  Gasket or a crack starting between them.

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All thank you for the suggestions. I'm starting to really think it's some sensor like Curt described, but which sensor would cause all 4 cylinders on one side to not combust?
Monday I will make an appointment with the repair shop to get a diagnostic hopefully I can get some answers... but it will be a few weeks...maybe I can convince the shop manager that I just bring the boat over hook it to the hose and the mechanic can hook up the code reader and give me a print out.

I plan on getting the Compression kit tomorrow and test it out....but 4 cylinders on one side with low compression...what are the chances?

**here is something that I noticed and I'm not sure if this was present before my troubles started. This only happens with the port engine (the one with issues)
When I turn the key, I hear the fuel pump pressurizing which is normal, then when I turn the key off, I hear a similar sound like the fuel pump but a bit louder (HUmm) for about 30 seconds and turns off with a click -- like a solenoid closing or opening. This happens if the engine runs or not. This sound does NOT happen on the Starboard Engine after turning the key off????????????????

So here are a couple more things I have done;
- Tested for Spark, all 4 wires produce spark on the port side
- Tested the plugs to the injectors with noid lights -- all worked, and has I removed each plug to test did not notice any change on the RPMs, so I tested one of the plugs on the starboard side, as soon as I pulled the plug, the engine almost died, and that one tested the same as the port plugs.
- Tested the injectors for continuity - ranged between 13 and 15 Ohms 
- Swapped the computers...no change

To summarize here is what I have done so far in addition to the above;
- New cap and rotor -- old one said it was marine approved but had aluminum posts and were all rusted (white chalky looking) - new ones have brass posts
- New plugs, gapped at 0.060 and torqued to 11 lbs
- Swapped Crankshaft Position Sensor
- Swapped Idle Control valve sensor
- Pulled a couple plugs after running it for a total of about 15 min - they are clean, they smell like fuel but are dry

Right now I'm getting ready to go and pull the injectors on the port side and see if they are clogged.
I'm tired of chasing my tail...

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Hang in there.  A few more tests?  Wingnut will higher you.  :)

All the cylinders on 1 side of a engine not firing ?  On a timing belt driven camshaft that is a very rare possibility. If a tensioner loosens or a belt stretches. The belt can add a tooth or subtract a tooth & cause power losses.  But that is a rarity. The cam timing change would fit all cylinders going weak.  Do not know if you have separate cams on each head.

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23 minutes ago, cyclops2 said:

Hang in there.  A few more tests?  Wingnut will higher you.  :)

All the cylinders on 1 side of a engine not firing ?  On a timing belt driven camshaft that is a very rare possibility. If a tensioner loosens or a belt stretches. The belt can add a tooth or subtract a tooth & cause power losses.  But that is a rarity. The cam timing change would fit all cylinders going weak.  Do not know if you have separate cams on each head.

I have no idea on the Cams.

Does anyone know how to get a hold of Wingnut? I have never contacted him, but from reading his posts, I would love to have his input on what this could be.

Again, thank you ALL for pitching in with suggestions... still trying to get the fuel rails off to take a look at the injectors to verify they are not clogged or the Port side rail is not clogged either.

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A totally / partially blocked rail could do it very nicely.  Is that the sooty sparkplug side ?

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50 minutes ago, Dozer said:

I plan on getting the Compression kit tomorrow and test it out....but 4 cylinders on one side with low compression...what are the chances?

Not real high.  I'm sure you know this, but just in case, some auto parts stores "rent" certain tools for free.  I was doing the rear brakes on my Son's vehicle a few months ago, and didn't have the tool to spin the parking brake ball screw back into the caliper pocket.  Went up to O'Reilly to purchase or rent one.  Learned they "rent" them for free.  I bought the pads from the dealer, but when I took the tool back, I ordered a set of NGK iridium spark plugs and purchased a few other things.  Interesting way to drive traffic.  At any rate, It'll be interesting to see the results.  Either way, this will help isolate the issue. 

53 minutes ago, Dozer said:

**here is something that I noticed and I'm not sure if this was present before my troubles started. This only happens with the port engine (the one with issues)
When I turn the key, I hear the fuel pump pressurizing which is normal, then when I turn the key off, I hear a similar sound like the fuel pump but a bit louder (HUmm) for about 30 seconds and turns off with a click -- like a solenoid closing or opening. This happens if the engine runs or not. This sound does NOT happen on the Starboard Engine after turning the key off????????????????

Can't help with this - I'm not there able to listen.  I sure would want to identify the sound though, even if it meant getting a buddy to work the key.

1 hour ago, Dozer said:

but which sensor would cause all 4 cylinders on one side to not combust

The ECT will kill fuel to 4-injectors when the engine is cold and the throttle is pushed past certain RPM set-points.  On Volvo Penta's of the same vintage, no audible warning when this happens but it's visible on the scan tool.  

Likewise, if protect mode is triggered from high heat (or a high heat ECT reading) for example, 4-injectors are killed if RPM's are above a certain level (generally 2,500 until below 1,200).  On Volvo Penta's of the same vintage, there is an audible alarm and it's visible on the scan tool. 

I don't know if Mercury's audible alarms function this way or not.  Regardless of Mercury or Volvo Penta, the scan tool will show what is going on.

1 hour ago, Dozer said:

- Tested for Spark, all 4 wires produce spark on the port side

I assume each was grounded-out on the port side, and each sparked with the plug seated.  Correct?  If so, there's spark and it's not a sensor killing spark.  There are only two things the ECM controls to protect the engine at the individual cylinder level - spark/no-spark and fuel/no-fuel (via the injectors).  If there's spark with the plug seated, we've narrowed to compression or more likely a sensor.  A few quick questions.  When new manifolds were replaced, were new exhaust temperature sensors/switches installed?  Was the hole pre-drilled (it should be a blind hole, not a thru-hole)?  Is the wire seated on both ends?  Is the wire good?  

1 hour ago, Dozer said:

-- all worked, and has I removed each plug to test did not notice any change on the RPMs, so I tested one of the plugs on the starboard side, as soon as I pulled the plug, the engine almost died, and that one tested the same as the port plugs.

The first part of this sentence indicates the port side is not running, for whatever reason.  What does this last part mean (..., and that one tested the same as the port plugs.")?

 

 

 

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So what is causing the no power condition on 4 cylinders ? Did you test for a HOT BLUE SPARK on each sparkplug lead ?. Using a good spare plug in a sparkplug lead and holding the metal plug body on a BARE METAL block place ? Did you get a great spark at ONLY the gap ?  Of deep down & out of sight in the insulator body.......Like a defective insulator can do ?

Hard to believe all 4 plugs are bad............... OR........... The ............Forgot you have coil & distributor cap..........Test run the engine with the old Aluminum cap again. New cap is bad ?

The sudden  failure to fire smoothly & then run better is like a electrical problem. Sooty plugs true.............. The overheating is hard to explain just at the same time ?........Not sure the WOT overheat is related to dead cylinders.

A read out will help get us back on track.  .............. Seems like 1/2 of the distributor is cross firing those 4 cylinders?  Even possible.

These massive parts changes are tricky. a bad new part start another trouble.  Hate that.

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Is there any chance the 4 plug wires were plugged into the distributor wrong sequence ?  check that first.

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1 hour ago, cyclops2 said:

A totally / partially blocked rail could do it very nicely.  Is that the sooty sparkplug side ?

When I pulled the rail from the injectors, fuel just poured out it -- so not blocked. Tested the injectors on the bench with 12V and can of pressurized seafoam. Clicked and sprayed even. So not the rail or injectors.

1 hour ago, cyclops2 said:

Is there any chance the 4 plug wires were plugged into the distributor wrong sequence ?  check that first.

Nope, I made sure to label them as I unplugged the old cap. This was the first thing I did to take care of this issue, because once I took that cap off and saw all the crap on the posts, I immediately went and go tow caps and rotors, -- the starboard engine was just as bad, so I figured get them both replaced. The engine still ran the dame as it did with the old cap.

1 hour ago, cyclops2 said:

So what is causing the no power condition on 4 cylinders ? Did you test for a HOT BLUE SPARK on each sparkplug lead ?. Using a good spare plug in a sparkplug lead and holding the metal plug body on a BARE METAL block place ? Did you get a great spark at ONLY the gap ?  Of deep down & out of sight in the insulator body.......Like a defective insulator can do ?

I had to wear gloves and hold the wire boot with a pair of pliers, as to not get shocked. The spark was strong and about 1 inch from the manifold it would get a nice spark

1 hour ago, Curt said:

Not real high.  I'm sure you know this, but just in case, some auto parts stores "rent" certain tools for free.  I was doing the rear brakes on my Son's vehicle a few months ago, and didn't have the tool to spin the parking brake ball screw back into the caliper pocket.  Went up to O'Reilly to purchase or rent one.  Learned they "rent" them for free.  I bought the pads from the dealer, but when I took the tool back, I ordered a set of NGK iridium spark plugs and purchased a few other things.  Interesting way to drive traffic.  At any rate, It'll be interesting to see the results.  Either way, this will help isolate the issue. 

Oh yea, I have been renting (deposit $$) tool kits from O'Reilly and other part stores for years. You're right, it's a great service and does drive customers to then buy the part they need...
Wish we had a marine parts store that did that... :) 
As for the pressure testing, I'm really not feeling it right now, maybe its the aching body and the disappointment of not being able to narrow down this issue. I figure I will just wait for the boat shop to diagnose it, and then go from there.  Right now I look like I have been in a fight with a cat, I'm all scratched up.

1 hour ago, Curt said:

Can't help with this - I'm not there able to listen.  I sure would want to identify the sound though, even if it meant getting a buddy to work the key.

I feel stupid on this one, figured it out. when the port engine is turned off the Bennet trim tabs motor runs for about 30 seconds, I guess to retract the tabs in case you forgot them down.

1 hour ago, Curt said:

The ECT will kill fuel to 4-injectors when the engine is cold and the throttle is pushed past certain RPM set-points.  On Volvo Penta's of the same vintage, no audible warning when this happens but it's visible on the scan tool.  

Likewise, if protect mode is triggered from high heat (or a high heat ECT reading) for example, 4-injectors are killed if RPM's are above a certain level (generally 2,500 until below 1,200).  On Volvo Penta's of the same vintage, there is an audible alarm and it's visible on the scan tool. 

I don't know if Mercury's audible alarms function this way or not.  Regardless of Mercury or Volvo Penta, the scan tool will show what is going on.

ECT?? what is it and where would it be located?
Now that you mentioned, when the boat first overheated it had a very loud alarm that is located under the dash. But since this issue has occurred, I have notice a faint series of beeps when I first turn on the engine. They are hard to hear, and I think it's about 3 or 4 and then goes away. I think I read somewhere this may be the "Guardian" kicking in. Any insight into this?

2 hours ago, Curt said:

I assume each was grounded-out on the port side, and each sparked with the plug seated.  Correct?  If so, there's spark and it's not a sensor killing spark.  There are only two things the ECM controls to protect the engine at the individual cylinder level - spark/no-spark and fuel/no-fuel (via the injectors).  If there's spark with the plug seated, we've narrowed to compression or more likely a sensor.  

Not sure what you mean by "Seated" I did not remove the plugs from the engine, I just used a spare plug and plugged into each wire one at a time, as I moved the plug near the manifold the spark started jumping as far as one inch away until I touched it to the manifold and had the spark jump from the center electrode to the ground prong on the plug.
I hope it's a sensor.... because this tail chasing is tiresome.

 

2 hours ago, Curt said:

When new manifolds were replaced, were new exhaust temperature sensors/switches installed?  Was the hole pre-drilled (it should be a blind hole, not a thru-hole)?  Is the wire seated on both ends?  Is the wire good?  

I don't have exhaust temp sensors/switches on my manifolds. There were none on the old ones. Absolutely no wires connected to the manifolds or risers.

2 hours ago, Curt said:

The first part of this sentence indicates the port side is not running, for whatever reason.  What does this last part mean (..., and that one tested the same as the port plugs.")?

Sorry for the confusion on this. I test each plug for each injector on the port side with the Noid light. As I unplugged, tested and plugged each there was no affect on the RPM's, and the Noid light flickered the same on all four. I then removed the plug from cylinder 2 (starboard side) to compare the flickering to the port side - That's what I meant ("..., and that one tested the same as the port plugs."). Also by removing the injector plug on cylinder 2 the RPMs dropped to the point the engine almost died.

 

I guess now I will wait, and as soon as I get a response from the boat shop, I will post it here... hopefully with the repair solution. I don't like to read UNSOLVED topics.

Again, thanks you for all the help and time, it's really appreciated.

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Well you have done as much DIY as is possible.  I am satisfied the Sensor or computer is reading a FALSE ERROR SIGNAL .  A read out is now required with the engine running. It should be throwing continuous errors about why those plugs are dead when running.

Not to anger you about this problem.

But this is why I really avoid Computers & FI in boats. ………..Most of us that post CAN TROUBLE SHOOT...………..But not when there are so many sensors that can cause a problem like this.

Curts reasoning about 4 plugs being shut down fits now. If it is the same 4 plugs that will fire by computer design.

But I can not see how you get sparks by using the test spark plug method. But the cylinders do not produce power. I comeback to they are not firing each cylinder at the correct time.

That would explain the new clean plugs smelling of gasoline. 

Hope you get a great mechanic.  Best of luck on a toughy to nail down. 

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15 hours ago, cyclops2 said:

If it can drop 4 cylinders when below 140 F.  How can you run the boat until 140 F is reached ?   What is the warmed up temperature  ? 

240, Please give the guy a break.

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9 hours ago, Dozer said:

ECT?? what is it and where would it be located?

Again, I'm not a Mercury expert but their respective EFI systems have some similarities with the same aim of efficiency and protection.  ECT is the engine coolant temperature sensor.  On Volvo Penta's of a similar year, there is 1 sensor that kills 4-fuel injectors under certain conditions when engine protect mode is engaged, the ECT.  In addition, there are 2 sensors that kill spark to 4-cylinders when engine protect mode is engaged, the exhaust temperature and oil pressure.   

9 hours ago, Dozer said:

I just used a spare plug and plugged into each wire one at a time, as I moved the plug near the manifold the spark started jumping as far as one inch away until I touched it to the manifold and had the spark jump from the center electrode to the ground prong on the plug.

Thank you for clarifying.  You've confirmed there's spark.  What we don't know is whether you problem is caused by killing 4-injectors or killing spark to 4-cylinders.  This is where the scan tool is quicker because what the engine is being doing can be seen.  At the same time, there is a way to test each one by one and based on the result (what the engine does), narrow the issue.

9 hours ago, Dozer said:

I don't have exhaust temp sensors/switches on my manifolds. There were none on the old ones. Absolutely no wires connected to the manifolds or risers.

Again, sorry, I'm not a Mercury expert.  I believe with any MPI (a.k.a. EFI) engine, though, the system needs input from the exhaust system (at least Volvo Penta's of the same vintage do).  Perhaps on a Mercury this sensor is not included or not located on the manifolds.  I don't know.  Wingnut will.

9 hours ago, Dozer said:

Now that you mentioned, when the boat first overheated it had a very loud alarm that is located under the dash. But since this issue has occurred, I have notice a faint series of beeps when I first turn on the engine. They are hard to hear, and I think it's about 3 or 4 and then goes away. I think I read somewhere this may be the "Guardian" kicking in. Any insight into this?

This is significant.  Glad you recalled this.  The system is shouting out two things.  First, what triggered or that engine protect mode was triggered (engine temp., exhaust temp. and/or oil pressure).  The original loud alarm.  Second (a.k.a.), a code was present.  It's basically an audible FYI.  If engine protect mode was active, the loud steady alarm would sound.  (Again, sorry, this how Volvo Penta's does it.  There are similarities, for sure, but also some differences.)

9 hours ago, Dozer said:

As for the pressure testing, I'm really not feeling it right now,

I'm with and you and feel the same.  In lieu of, look to see if there is any sign of leakage (e.g. not torqued, gasket blow-by, etc.).  If none, I doubt it's compression.

 

9 hours ago, Dozer said:

I guess now I will wait, and as soon as I get a response from the boat shop, I will post it here... hopefully with the repair solution. I don't like to read UNSOLVED topics.

Don't give up, you are closer than you think to solving... just in the "trough" at the moment.  Take a breath, give it a day perhaps, but you are close.  Yes, a scan tool would allow almost immediate gratification (the solution), but you've practically rounded 3rd and home plate is insight.

Wingnut posted a site that has Mercury parts and schematics.  I'll find it and see if an exhaust temperature sensor can be confirmed and a few other things.   

In the meantime, consider two things. 

First, we've not discussed oil pressure.  Is it good, right weight oil and type, not over/under filled, etc.? 

Second, given everything you've described, it seems there's a bad ECT or its wiring is chaffed or one/both terminations aren't fully seated or there are damaged pins.  Yes, I need to confirm if there's an exhaust temperature sensor as well.  Working on it.

  

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13 minutes ago, Curt said:

Again, I'm not a Mercury expert but their respective EFI systems have some similarities with the same aim of efficiency and protection.  ECT is the engine coolant temperature sensor.  On Volvo Penta's of a similar year, there is 1 sensor that kills 4-fuel injectors under certain conditions when engine protect mode is engaged, the ECT.  In addition, there are 2 sensors that kill spark to 4-cylinders when engine protect mode is engaged, the exhaust temperature and oil pressure.   

Thank you for clarifying.  You've confirmed there's spark.  What we don't know is whether you problem is caused by killing 4-injectors or killing spark to 4-cylinders.  This is where the scan tool is quicker because what the engine is being doing can be seen.  At the same time, there is a way to test each one by one and based on the result (what the engine does), narrow the issue.

Again, sorry, I'm not a Mercury expert.  I believe with any MPI (a.k.a. EFI) engine, though, the system needs input from the exhaust system (at least Volvo Penta's of the same vintage do).  Perhaps on a Mercury this sensor is not included or not located on the manifolds.  I don't know.  Wingnut will.

This is significant.  Glad you recalled this.  The system is shouting out two things.  First, what triggered or that engine protect mode was triggered (engine temp., exhaust temp. and/or oil pressure).  The original loud alarm.  Second (a.k.a.), a code was present.  It's basically an audible FYI.  If engine protect mode was active, the loud steady alarm would sound.  (Again, sorry, this how Volvo Penta's does it.  There are similarities, for sure, but also some differences.)

I'm with and you and feel the same.  In lieu of, look to see if there is any sign of leakage (e.g. not torqued, gasket blow-by, etc.).  If none, I doubt it's compression.

 

Don't give up, you are closer than you think to solving... just in the "trough" at the moment.  Take a breath, give it a day perhaps, but you are close.  Yes, a scan tool would allow almost immediate gratification (the solution), but you've practically rounded 3rd and home plate is insight.

Wingnut posted a site that has Mercury parts and schematics.  I'll find it and see if an exhaust temperature sensor can be confirmed and a few other things.   

In the meantime, consider two things. 

First, we've not discussed oil pressure.  Is it good, right weight oil and type, not over/under filled, etc.? 

Second, given everything you've described, it seems there's a bad ECT or its wiring is chaffed or one/both terminations aren't fully seated or there are damaged pins.  Yes, I need to confirm if there's an exhaust temperature sensor as well.  Working on it.

  

No exhaust temperature senders on a 2006 5.0 MPI. There should be IMHO but there are none. This one is a real PITA but you will eventually get it. I hate the GM based distributor used on these engines as brand new caps right out of the box have left me down. Just for the sake of discussion, I would look inside of the new cap and look for carbon tracking. Cam offset angle is so critical to rotor/cap phasing on these engines. W

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