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2016 Sunesta 224 won't plane with full fuel tank


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I've been fighting some mechanical issues for this "new to me" boat that sat neglected for a few years (bank repo)

The bank changed the fuel pump and needed to drain/flush the trim cylinders had that water in them.  When I got it I had a guardian alarm for low water pressure and needed to change the impeller.  From a previous thread I found an incomplete cap assembly on the gear oil reservior tank that was causing gear oil to dirty up my bilge.

Still wasn't running well (only would turn maybe 3800 rpm) - but with a few cans of Sea Foam and some fresh fuel it was running like a champ.  4500 rpm with light loads - jumping right on plane out of the hole.

Here's where it gets weird.  Out with a full lot of 4 adults and 4 kids yesterday and everything was fine.  Pulling all four kids on an oversized tube and she got rigth on plane and performed great.  BUT... that was with nearly dry tanks.  Drove to the gas dock and put in 40gal of fuel - and now the boat is a pig.  Max RPM maybe 3300-3500... won't plane... only will get to 12-14mph.  Didn't matter if we had the tube in the water or not.  Tried moving everyone to the bow to help (again 8 of us on the boat... 4 adults and 4 kids).  But night and day before and after getting fuel..... Strange??? 

Oh, and looking at other forum posts and videos - I was going to change the fuel filter... but there is not a external fuel filter/water seperator that I can see.  Only the small cartiage filter in the fuel pump which I assume is brand new if they changed that whole assembly.  (maybe I should check to see if it sucked in any junk from the tank?)  Only other thing I can think of is ignition issues... mabye fouled plugs?  Any other ideas?

 

 

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No idea on the prop(s).  It's a Bravo3 with duel props.  Assuming it's whatever came stock from Chaparral so guessing that's not an issue.  But I just treked down to the marina on a hunch and hit paydirt... well fuel dirt that is.  Dirty fuel filter.  Had assumed it was not an issue since the whole fuel pump/cooler assembly was just changed. but must have been some left over sediment in the tank - because the new filter is toast.

Anyone happen to know if that basket paper in the photo is a pre-filter or is it "after" the cartridge above it in the Mercruiser fuel pump/cooler assembly?  The cartriage looked fine... but if all that got through - it's likely restricted as well???

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  • 1 month later...

Update... been fighting intermittent low power (won't plane) for a month now.  Seemed to have a pattern of worsening when the engine was hot - also was getting Guardian alarms at times when the power was good and I was at higher speeds.  Finally broke down and got my hands on a Rinda scan tool to stop guessing.  Still somewhat in the dark because I don't have the proper Mercruiser plug adapter till later in the week (standard tool connector doesn't work - I have a 2016 engine with catalysts and it takes as special box) - but the limited CAN read was saying Engine Misfire (SPN1322) and an Injector problem (SPN 651 -Low voltage or shorted) - seem related, right?

Fun part follows - was running around a bit and the engine got really rough - lots of intermittent hesitation - much worse than before with only intermittent low power.  Of course I had my Rinda tool still plugged in - and now a new fault shows up out of the blue... SPN 626 - Crank Position Sensor - Data erratic, intermittent, or incorrect.  What are the odds that the stupid Crank Sensor fails while I'm out running diagnostics, but I verified that code wasn't stored or active before today?  Did order a new sensor after first checking to make sure the connector was tight as the boat is running much rougher (even stalling occasionally at idle) since that fault surfaced.

Few questions:  I don't have a manual - but can you change the Crank Sensor without removing any of the front end belts/pulleys?  Seems pretty tight down there in my 224 Sunesta engine "room" but I think it's worth a shot to save the trouble?  Also, I read  on another site that removing the injectors is tricky... recommended using some PB Blasters to loosen them up.   Also said to depressurize the rail first.  Is that just done by cranking with the fuel pump disconnected like the old engines?  Likely will pull all 8 injectors down the road to have them tested/flowed... but just want to get running so I ordered #1 to swap asap.

New Rinda plug due later this week and I'll update the thread with the "history" insights I can pull about past faults and guardian reasons.  What a mess!  

 

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stalling at idle and rough running are for sure symptoms of a bad crank sensor.  However,WOT loss of power is generally not a bad crank sensor., that's fuel/filter - perhaps distributor cap ignition wires, etc. 

Yet your boat is 2016  - those sensors are pretty simple things perhaps its wiring/plug from the sensor.  Check to make sure no issues with the sensor wire or breaks in the wire..

Don't worry about pulling the belt -its super easy, only takes two wrenches (16mm & 8MM on the tensor pulley)  -  mercruiser belts are not tightened very tight -  just take a picture to remember the belt pattern.   As FYI -  youtube can help - lots of videos pull the belt - like when you change the impeller on the sea pump.

 

Let me know what engine you have.   My manual is on the boat, but I'll pick it up tonight. 

 

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Crank position can control a lot of bad running at all speeds.

That very old fuel is probably coming loose and  into your filter a lot. 

Sensor & the filter change first.  Then see if it revives.

Someone else just had a crank sensor die. Similar complaints

Repo boats are usually run into the ground.  Might want to do a full plugs to distributor change. Could do wonders for not much money.

The can of SeaFoam in the tank just before you reload the tank .  Tank may have enough junk to bock a couple of filters.

Just remember........... Boat ran fine until a full load of gas stirred up & disolved crud.  Or is bad fuel load. Keep checking / cutting open the filters to see the crud.  Water stirred up in the supplier tank can cause some of your problems also.

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Thanks to you both for the insights.  Couple added points - we've probably been through 4 tanks of good marine dockside fuel and a half a dozen cans of SeaFoam since my first blocked filter change.  Also added an external Raycor oversize (60gph) filter/water separator a few tanks ago when I suctioned the tank dry so I'm guessing the fuel going in now is solid.  Still doesn't help if gunk got past previously and is being stirred up in the rail or still working its way through the injectors (or not!)  Assume the fault I'm getting for the #1 injector (low voltage/short) is more than a blockage or does that line up, i.e does a plugged injector freeze and present itself as an electrical issue?

Oh, and thanks for the plug/distributor/wires suggestion.  Did that separately (plugs first) to see how much incremental improvement was to be had.  Plugs helped significantly.  Did cap/rotor yesterday right before the crank sensor fault showed up... so haven't gotten a read on if it was beneficial.  Wires tbd (too hot yesterday).  Plugs were in pretty bad shape (chalky tips and very rusty outside) and distributor cap contacts were not great either.  Existing wires look ok...but I'll change anyway.

One more thing... @JPW - we might be neighbors.  I see in your profile that you're in NE Ohio.  Where are you docked?  I'm in CLE at Edgewater.

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Another update for those following (laughing at my stupidity).  With the better Rinda adapter I found the “crank” sensor error to actually be a “cam/crank” sensor error.   Upon further investigation I realized that I had mistakenly unplugged the Cam/Hall Effect sensor under the distributor when changing out the cap/rotor.  Easy fix (little embarrassing) but now I’ve narrowed my issues down to an intermittently faulting injector #1 and a fairly regular Guardian alarm for high Port Side ECMT sensor temperature.   

 

Injector issue seems straight fwd.  Need to pull and have those flow checked to eliminate the bad fuel struggles of the past (any service manual help on that would be much appreciated).  As for the Guardian - after any decent run at 50%+ throttle - my exhaust manifold temp on the port side builds to 212 and the Guardian cuts power to 5%.  Starboard manifold temp (164) and main ECT (159) are fine - just the high temp on the Port side.  
 

Any ideas on the possible cause.  Sensor seems responsive- feels like a legit reading.  Had a bad sea water pump impeller and it was replaced a few months back.  Maybe a chunk got downstream and is partially blocking something?

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New injector due tomorrow according to UPS.  Still curious if all 3 of my "faults" might boil down to the one problem injector?  In summary - I have active codes for an "Injector 1 Output Fault" (Mercury Fault 340/SPN 651), I'm seeing high Port EMCT leading to a Guardian Alarm under load (~214 deg), and also in the RINDA tool I see some misfires in the history (cylinders 1,2,7,8... but highest count for #7?).  Hoping all are intertwined and I'm not going to be chasing yet another issue when I fix the injector?  Any guidance @Wingnut   With Injector #1 on the Port side of the block - seems like more than a coincidence that my miss, bad injector, and high temps all line up on that side?

Also - with this being my first time dealing with gasoline injectors (I'm a diesel guy - ex Cummins engineer) are there any tips/tricks for remove/install?  I've heard the advice to kill rail pressure by cranking with the fuel pump disabled, lots of PB Blaster to help free the injectors from the block, new o-rings... but anything else?  Do I just remove the bolts/fuel rail... and then wiggle the injector free from the head?

Final question - guessing I should have all 8 injectors tested because if water got to #1... likely others might be partially affected.  Hate the idea of pulling all 8 and waiting a week+ for servicing/shipping back and forth (short boating season in NE Ohio... every week counts!)  Does anyone do swaps where you get 8 freshly rebuilt injectors and then give them your cores after the swap which get passed to the next guy - or is that not a common practice?

 

Thanks in advance!!!

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  • 1 month later...

Quick update- Guardian alarm issue for high EMCT finally was resolved.  Found two pieces of the old impeller wedged in the output hose fitting blocking water flow.  
 

Thought my issue of poor performance when hot would rectify itself now that I’ve solved this major water flow /cooling issue but much to my dismay - same situation occurs.   Boat runs flawlessly cold- first run - for about 45 min to an hour.  Then it loses about 50% of its power.  Depending on how much it’s loaded it either struggles to plane or just barely can be coaxed to plane.  Typically bogged down to about 2500 rpm max or ~12 mph.  Almost as if the second 1/2 of the throttle doesn’t exist.  
 

Having the boat “rest” for an hour to cool down has no improvement- only the next day will things return to normal.   So strange!!!!

 

I’ve had friends suggest a bad fuel tank vent but I’ve tested and it’s clear nor do I get any air “woosh” when I crack the fuel fill.  I’ve changed all the electrics (plugs, distributor cap/rotor) and both low and HP fuel pumps.  Fuel filters new.  
 

Just can’t explain why it’s fine for an hour and then goes to crap every time !!!???!!!  Any suggestions on what to check next?  @Wingnut

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11 hours ago, Buckeye94 said:

Quick update- Guardian alarm issue for high EMCT finally was resolved.  Found two pieces of the old impeller wedged in the output hose fitting blocking water flow.  
 

Thought my issue of poor performance when hot would rectify itself now that I’ve solved this major water flow /cooling issue but much to my dismay - same situation occurs.   Boat runs flawlessly cold- first run - for about 45 min to an hour.  Then it loses about 50% of its power.  Depending on how much it’s loaded it either struggles to plane or just barely can be coaxed to plane.  Typically bogged down to about 2500 rpm max or ~12 mph.  Almost as if the second 1/2 of the throttle doesn’t exist.  
 

Having the boat “rest” for an hour to cool down has no improvement- only the next day will things return to normal.   So strange!!!!

 

I’ve had friends suggest a bad fuel tank vent but I’ve tested and it’s clear nor do I get any air “woosh” when I crack the fuel fill.  I’ve changed all the electrics (plugs, distributor cap/rotor) and both low and HP fuel pumps.  Fuel filters new.  
 

Just can’t explain why it’s fine for an hour and then goes to crap every time !!!???!!!  Any suggestions on what to check next?  @Wingnut

You may have tweaked a head gasket during all the overheating events. Time for a compression and leak down test. Sometimes they will introduce cooling water into a cylinder or two after warm up, but not on a cold engine. Pay particular attention to what each plug looks like when you remove them.   A bad coil will also degrade when it gets hot. W

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@Buckeye94 last summer I bought a 2008 Sunesta 284 that sat for 6+ years on a lift.  Long story short, I spent weeks and a ton of hours fighting a similar problem, but mine would just cut out for no apparent reason at higher rpm's and stutter at lower rpm's.  We put a fuel gauge on the rail and it was showing 40-45psi and would just drop to 0.  After pulling apart the fuel system, replacing filters, using mechanics laptop to track sensor potential issues (we got a random camshaft sensor error once).  It turns out I had "trash" in my fuel tank that would get sucked up in the pickup line that is inside the fuel tank because there is a little metal screen on it.  We pulled that things several times before we finally found something stuck to it...the trash would get sucked onto that screen and then fall off.  If you have trash, sediment in your fuel filter then I'd bet you have more in that tank still.

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Thanks @Stretch79   Appreciate the comments.  I too had crap in the fuel tank and believe that was driving some of my early issues.  Since then I've completely vacuumed the tank dry and added a Raycor pre-filter (screw on with a metal bowl) prior to the Merc Cool Fuel3 on-engine system.  No more water/old ethanol in the system as I've checked both Merc filter/screen as well as drained the bowl and it comes out clean.

This one is acting like a clock... every time just konking out at the same 45-60min mark and then "resetting" itself when it cools off.  So strange?!?!?!?

Thanks again for your post and glad your 284 is  back up and running.

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Correct @cyclops2... the BEEPING (Guardian) alarm is done.  That was confirmed a month ago as the Port side ECMT overheat.  My cooling issue is in the rear view mirror.... Now just trying to understand why after the boat heats up I lose 1/2 of my throttle.  Not sure if it helps troubleshooting...but this problem was present before (hence the title of this thread).  Thought it was due to a full tank of fuel, but that was just happenstance.  So happened that I ran for a while (fine) - pulled into the marina for fuel and then when I went back out... no power.  Same thing now occuring independent of fuel.  Doesn't matter if fresh/old... full or empty tank.  Only varriable that matters is cold/hot.  :)

Just ordered the leak down test kit for Amazon for $30.  Won't be able to check that 'till Thursday.  Curious if there's any specs I can check (both hot and cold) with my multi-meter on the coil to see if that's the culprit.  Hate to buy a new one to "test" at $300... but after screwing around with manifolds and risers and fuel pumps... that would be a bargain!!!!

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O K   Quick test to help weather it is fuel or ignition. 

When the slowdown occurs. Is the engine back firing at that speed if you move the throttle to FULL SPEED ?  Or does it just moan & put out a blackish sooty exhaust ? Hang over the transom to see or smell the exhaust .

If none of the above is happening ?   Just a feeling of a smooth running stuck at 1/2 throttle ?

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5 hours ago, Buckeye94 said:

Thanks @Stretch79   Appreciate the comments.  I too had crap in the fuel tank and believe that was driving some of my early issues.  Since then I've completely vacuumed the tank dry and added a Raycor pre-filter (screw on with a metal bowl) prior to the Merc Cool Fuel3 on-engine system.  No more water/old ethanol in the system as I've checked both Merc filter/screen as well as drained the bowl and it comes out clean.

This one is acting like a clock... every time just konking out at the same 45-60min mark and then "resetting" itself when it cools off.  So strange?!?!?!?

Thanks again for your post and glad your 284 is  back up and running.

I missed that part reading through all of the posts.  I'm curious, do you have the part# for the pre-filter?  Also, did you remove the screen in the pickup line inside the fuel tank since you installed that pre-filter?  I might do this to mine since I did not clean out my tank 100%.

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Do you have a water cooled fuel line ?  Feel it up when the engine goes to 1/2 power.  Is there a warning horn during the 1/2 power condition ?

 on a car with a centrifugal advancing ignition. You would get your condition of smooth reduced power. 

So we need to find out what controls the automatic advance of timing .Not another Crank Position Sensor ?

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 - So the fuel filter/pump assembly is water cooled (CoolFuel3) but fuel line up to the rail is open to the environment.

  -No warning horn during the 1/2 power state.

I'm waiting for the kit to test compression leak down (suggested by @Wingnut) but really starting to feel something electrical is heat soaked and causing the motor to limp  - coil, sensor, (gulp?) ECM?   So much packed in up top between the heads and no positive ventilation in the compartment.

Took the boat out today and couldn't reproduce the condition.  Besides riding solo and not being loaded up (3 kids, 3 adults + tube) - one difference from Sunday when I had my 1/2 power issue was that I pulled the beauty cover from the top of the engine to screw in the fuel gauge (left it off) and also lifted the hatch every few minutes to read the pressure gauge.  Maybe the extra air flow was all that I needed to prevent the condition?  Doesn't solve my problem... but good for troubleshooting. ;) 

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So it ran much better with the engine cover off ? Is the engine cover damaged ? Check the air inlet holes in the engine cover.  What electrical parts are under  /  in   the engine cover ?any sensors ? A air temp sensor ?

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4 minutes ago, cyclops2 said:

So it ran much better with the engine cover off ? Is the engine cover damaged ? Check the air inlet holes in the engine cover.  What electrical parts are under  /  in   the engine cover ?any sensors ? A air temp sensor ?

When I say "cover" it's just a simple beauty plate that sits on top of the flame arrestor (1 1/2 x the size of a dinner plate)  Not all that confident what's all is under the cover... IAC valve, MAP /Temp sensor... but definitely the main engine ECM.  (hoping that's not the culprit at $1,500 - ugh!)

 

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Check every sensor for a good plug connection. The boat DID  DID run great for a time. Are you still buying  gas from the place that caused the first 1/2 power running ?

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