biagio154

mercruiser 5.0 EFI cuts down at high speed

22 posts in this topic

Hello Guys, how is everyone doing?

I have a two year old dilemma with my boat and after trying to resolve the issue on my own I now realize that it is the time to seek the wisdom and knowledgeable expertise of some of you fellows.

Here is my problem (which started last year toward the end of the season): The Mercruiser 5.0 EFI in my 2002 Chap 240 starts fine and gets up to good high speed (3500+ RPM), the boat will plane fine and then after about 3 to 5 minutes into the ride the engine suddenly cuts down to a very rough idle speed and wile it will not shot off completely it sounds like is going to. When I shot down the engine myself and restart after 30 secs.it will maintain a very rough speed up to about 1000 RPM but when I try to increase the RPM it will choke and shoot down, so I have to keep at that very low speed to maintain the engine on and slowly make back to the marina.

After a long wile (the engine cools down maybe?) everything goes back to normal and the next day

the engine will perform properly again, sometime even for the duration of about a week and then suddenly it will do this erratic and frustating nonsense again.

I have checked for water in the fuel system many times but it was always clean. At the beginning of the season I even changed the electrical fuel pump as a precautionary measure, although it did sound in good working order, I changed the thermostat and water pump impeller kit, the engine oil level and pressure are fine, oil level of the outdrive reservoir is at the proper level, check for obstructions in the water pick-up, and check so much more other things, but I cannot find anything that could be at fault. It is a real frustating dilemma!!!!

I talked to the marina's mechanic about this: he has not clue to what it could be, and he does not have the on board diagnostic computer for my model engine to check but he made a list of possible causes that was a mile long (a lot of which made absolutely no sense to me) and for an unspecified amount of deer's, of course, he said that he would look into until he finds the problem. (???!!!)

Not exactly the kind of answer that anybody would like to hear from a "reputable and expert" mechanic.

I understand that this engine has built in some precautionary safety system designed to protect the engine from damage if improper conditions are present.

Does anybody knows the specifics about this safety system and how it works?

Is any of this information on the Mercruiser manual or other literature?

And if yes where can I find them?

So far, I have managed to make back to port and put the boat back inside the slip without the aid of Boat-US, but I am concerned also for safety, so even when the boat runs fine I keep inside the relative safety of the Jamaica Bay and not longer venture out in the ocean or take those nice family strolls around NYC that we used to enjoy. Very disappointing!

I greatly appreciate any help with this issue.

Thanks guys

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Sorry to hear about your problems. You need to forget about your "mechanic" and find a Mercruiser technician trained to work on your engine and who has the diagnostic computer needed to "read' what's going on electronically with your engine. It sounds to me like either a bad sensor or a bad computer. Since the computers themselves rarely go, it's probably a bad sensor. To find out which one, the computer needs to be read. Please stop throwing money, parts, and wasted time at the problem. Find a real Mercruiser technician. Hy

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If it was the limp home feature or a bad sensor, you would be hearing at least 2 beeps every 45 seconds if it was a minor problem, and a continuous beep if the electronic control unit went into full protection mode.

Since you are not hearing the beeps, my guess is that it is not sensor related, but voltage related. The ECU requires a constant 12.5-13.5 volts to work properly. If is gets less than this or the voltage is erratic, it can have intermittent random problems.

I would first check to make sure that your batteries are being properly charged by your alternator, check the voltage regulator on the alternator for correct voltage output (usually at 14.4 volts or higher at 1000 RPM). Also check the battery to make sure that it will hold a charge by load testing it. Lastly, check to make sure that all battery cables are FIRMLY attached to the battery posts, tighten the wing nuts if needed. Also check for corrosion of the battery cable connectors at the battery, and check for clean battery posts. If corroded, clean the battery posts and connectors, and reattach using dielectric compound to reduce corrosion.

Also check the battery cable connectors for corrosion in the battery cable wires under the connector. Lots of people miss this, and it leads to erratic voltage which can cause the ECU to malfunction.

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Intermittent problems are a b@stard to fix.

Seeing what your symptoms are though, I'd opt for the following seeing you have a 5.0L EFI MerCruiser. (throttle body) You don't mention which drive you have, but I'm assuming the boat has a Bravo 3.

#1. Replace the ignition sensor under the distributor cap and rotor. There was a bulletin back in the day about some iffy sensors that would give poor running or a no start condition. (running the MerCruiser Thunderbolt style ignition) 5.0L MPI motors use a Delco ignition system. You'll want a new rotor too, and probably need a cap.

MerCruiser ignition sensor assy (updated and more robost style) # 87-892150K02 or Q02.

MerCruiser V8 cap & rotor kit # 805759T3 or Q3.

If you have MerCruiser 5.0L EFI (not be confused with the 2002 and newer MPI model) and the bugger won't start or runs rough, my first guess would be the ignition sensor under the distributor cap if you have the Mercury ignition. Merc had a bad batch of sensors back in the day - MerCruiser Service bulletin 2000-14) The Delco distributor didn't suffer from this affliction. NOTE: neither the gray or black sensors made by 'Cherry' were worth a d@mn IMO.

MCbulletin2000-14.jpg

MCbulletin2000-14001.jpg

MCbulletin2000-14003.jpg

If you have the Mercury ignition, and need a new sensor, the new part # is 87-892150K02 or Q02. The dist. rotor will most likely be badly mangled when removed. Merc # 13524T1 for V8 power, or 13524a6 for V6 power. The rotor can be a proper b@stard to get off too.

Like Jeff stated, check the battery cable connections, especially around the starter motor. EFI/MPI talks to itself and with its sensors by voltage, and loose wires can cause a bad case of 'telephone'.

Lastly, if you have an Alpha 1 drive, I'd switch out the neutral safety switch, part # 87-808009a3. I've seen this item causes problems by retarding the engine timing...Bravo doesn't use this switch.

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hey Professor how you do?

I aggree with you, I need to perform a full diagnostic and read the stored data of the ICM , but unfortunatelly, in order to do this I have to take the boat out of my marina and bring it to another marina with a reputable meccanic because no outside meccanics are allowed to work into GATEWAY, my marina. Talking with fellow boaters around here it turn out that this will be a very tough task because the reputations of these marinas meccanics around here are very questinable. Maybe I can found and rent the diagnistic ICM tool and perform a reading myself, which, accorderly with the manual, is fairly easy to do.

do you know of any of such possibility?

The fuel pump that I changed was the original one and pretty old so I do not feel so bad about changing it, the rest of the parts that I changeg were part of yearly mantainance as well, so no harm done there anyway, but this is very little consolation because I still remain with my problem to resolve.

Thanks for being there so quickly PROF. it is allway a pleasure talking to you

By the way how is you windlass anchor working? mine is fine although i need to change my rope to something a little more stiffer in consistency to get a better performance

ciao

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If it was the limp home feature or a bad sensor, you would be hearing at least 2 beeps every 45 seconds if it was a minor problem, and a continuous beep if the electronic control unit went into full protection mode.

Since you are not hearing the beeps, my guess is that it is not sensor related, but voltage related. The ECU requires a constant 12.5-13.5 volts to work properly. If is gets less than this or the voltage is erratic, it can have intermittent random problems.

I would first check to make sure that your batteries are being properly charged by your alternator, check the voltage regulator on the alternator for correct voltage output (usually at 14.4 volts or higher at 1000 RPM). Also check the battery to make sure that it will hold a charge by load testing it. Lastly, check to make sure that all battery cables are FIRMLY attached to the battery posts, tighten the wing nuts if needed. Also check for corrosion of the battery cable connectors at the battery, and check for clean battery posts. If corroded, clean the battery posts and connectors, and reattach using dielectric compound to reduce corrosion.

Also check the battery cable connectors for corrosion in the battery cable wires under the connector. Lots of people miss this, and it leads to erratic voltage which can cause the ECU to malfunction.

Thanks Jeff, I will check the batteries and their connections, although since my problem starter last year i did remove, trickle charged, and then reinstall the batteries at least once at the begging of this season, I will also check the connection by the starter like Shepperd is suggesting (that was never checked) and see if there is a loose of faulty connection.

Thank you Jeff and Sheppard!!

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Intermittent problems are a b@stard to fix.

Seeing what your symptoms are though, I'd opt for the following seeing you have a 5.0L EFI MerCruiser. (throttle body) You don't mention which drive you have, but I'm assuming the boat has a Bravo 3.

#1. Replace the ignition sensor under the distributor cap and rotor. There was a bulletin back in the day about some iffy sensors that would give poor running or a no start condition. (running the MerCruiser Thunderbolt style ignition) 5.0L MPI motors use a Delco ignition system. You'll want a new rotor too, and probably need a cap.

MerCruiser ignition sensor assy (updated and more robost style) # 87-892150K02 or Q02.

MerCruiser V8 cap & rotor kit # 805759T3 or Q3.

If you have MerCruiser 5.0L EFI (not be confused with the 2002 and newer MPI model) and the bugger won't start or runs rough, my first guess would be the ignition sensor under the distributor cap if you have the Mercury ignition. Merc had a bad batch of sensors back in the day - MerCruiser Service bulletin 2000-14) The Delco distributor didn't suffer from this affliction. NOTE: neither the gray or black sensors made by 'Cherry' were worth a d@mn IMO.

MCbulletin2000-14.jpg

MCbulletin2000-14001.jpg

MCbulletin2000-14003.jpg

If you have the Mercury ignition, and need a new sensor, the new part # is 87-892150K02 or Q02. The dist. rotor will most likely be badly mangled when removed. Merc # 13524T1 for V8 power, or 13524a6 for V6 power. The rotor can be a proper b@stard to get off too.

Like Jeff stated, check the battery cable connections, especially around the starter motor. EFI/MPI talks to itself and with its sensors by voltage, and loose wires can cause a bad case of 'telephone'.

Lastly, if you have an Alpha 1 drive, I'd switch out the neutral safety switch, part # 87-808009a3. I've seen this item causes problems by retarding the engine timing...Bravo doesn't use this switch.

Thanks Shapperd, you guessed right my drive is a Bravo III. I am not sure about the distibutor cap and ignition sensor simple because for the most part the engine run fine: it has plenty of power at all speed ranges, no esitations, nor miss firing, or detonation and it does have this malfuntion only sporadically and then the next day it goes back to normality. Loose connection or bad sensors maybe more probable.. What are the sensor involved with the safety shot off protection system? is there any litterature about it?

Thanks again

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Biagio: I had forgotten about the ignition module problem Shepherd mentioned. That's a strong possibility and not impossible, though difficult, to replace. You state you're in Brooklyn/Long Island. There are many good marine mechanics in those areas. You're just going to have to look. Yes, you may have to take the boat to a different marina for it to be checked out. Unfortunately, many marinas do not allow outside mechanics to work on boats docked there. I've got the same deal with the marina we're at. The windlass worked out fine. I need to replace the bolt holding the bow roller because it's too short, so the roller doesn't roll. When i first tried to use the windlass a few weeks ago, it locked up. I had wired the switch backwards, so Up was Down and Down was Up. I had to remove the dash panel and the switch and turn it over. No big deal. Stay safe. Hy

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On a scale of 1-10 (1 being easy, and 10 being hard), I'd say replacing the ignition sensor under the distributor/rotor to be a 7. For a guy who's handy with doing a tune-up on their car, this job in well within their realm of comfort.

Seeing you have the Bravo 3 drive, there is no cut-out switch issue like the Alpha.

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If it was the limp home feature or a bad sensor, you would be hearing at least 2 beeps every 45 seconds if it was a minor problem, and a continuous beep if the electronic control unit went into full protection mode.

Since you are not hearing the beeps, my guess is that it is not sensor related, but voltage related. The ECU requires a constant 12.5-13.5 volts to work properly. If is gets less than this or the voltage is erratic, it can have intermittent random problems.

I would first check to make sure that your batteries are being properly charged by your alternator, check the voltage regulator on the alternator for correct voltage output (usually at 14.4 volts or higher at 1000 RPM). Also check the battery to make sure that it will hold a charge by load testing it. Lastly, check to make sure that all battery cables are FIRMLY attached to the battery posts, tighten the wing nuts if needed. Also check for corrosion of the battery cable connectors at the battery, and check for clean battery posts. If corroded, clean the battery posts and connectors, and reattach using dielectric compound to reduce corrosion.

Also check the battery cable connectors for corrosion in the battery cable wires under the connector. Lots of people miss this, and it leads to erratic voltage which can cause the ECU to malfunction.

I had exactly the same problem on my mercruser check your battery its eather bad or going bad yes it starts np and runs acc's np but not enough power for the

efi good luck

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Thanks guys you are all very help full and your input is greatly appreciated.

Yesterday I started checking things out following your suggestions and so far this is what I find out:

My Battery#2 is going bad, so I will replace it today, but Battery#1 if fine.

I checked all terminals and connections. There was no sign of corrosion anywhere and all connection were good and tight with the exception of the Starter connection which was a little loose, of course, I tie up the nut and now if fine.

Today I will check the alternator output, although it looked like it was charging battery #1 (I disconnected bad #2), in fact, after I start the engine, I could see the voltmeter on the dashboard move up and slowly pass the 13 volts marker by a little fraction? Is it good or weak?

I also checked the anti-siphoning valve on top of the fuel tank for obstructions using some practical disgusting methods; It looks like is in good working order,

I also checked the fuel line going to the water separator; is the new USCG approved type, and there is not visual sign of any damage o deterioration do to alcohol in the fuel,

So I figured these are less thing to be worry about.

After I did all of the checking and perform the little intervention that I could, running just on battery #1(forget to shot-off the refrigerator thought) I took the boat out for a spin.

And sure enough it did it again! 2 miles into the run it shot-off again, and this time paying more attention, I also noticed that above3000 RPM there was not proper increase of power and very little speed increase on the boat as well.

It looks like is time to move to next step and look into the Ignition Sensor and the rotor like Shepherd is very eloquently suggesting, thank you Shepherd.

Also wile taking the stroll to nowhere fast, I noticed that it also sounded like my transom bearing is on is way out or maybe already gone.

Great!!! One other thing that I will be messing with in the very near future!

And some people say that boats are not FUN!!!!

Well I am the one who wanted a boat anyway so the FUN goes on. :0)

I Will keep you informed guys

Thanks Again

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Check your anti-siphon valve at the fuel tank outlet. Had a chunk of glass mat in one on a Sea Ray with your engine which showed up whenever it felt like it. Same issues as yours.

W

The anti-siphon valve

The anti-siphon valve installed at the fuel tank outlet fitting is a spring loaded ball poppet valve that prevents the contents of the fuel tank from siphoning into the bilge in the event of say a fuel line failure. In order for the valve to open allowing fuel flow, the fuel pump needs to exert a negative suction pressure. Failure of the pump to establish this vacuum condition will cause the type of situation you described. Also make sure the separator/fuel filter and fuel line fittings are tight as it is in the pump suction and could be leaking air. Before cranking, leave the key in the on position for several seconds in order for the fuel pump a chance to prime and fully pressurize the fuel rail. The fuel pressure regulator (a separate element on MPFI) may also be leaking down when the engine is shut off. A fuel pressure check at the fuel rail will confim this and aid with finding the problem.

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Wingnut has brought up a very possible issue. Sometimes running an engine on an outboard tank can eliminate what is wrong or right with an engine. One would need a 6 gallon tank though for any kind of true test...highly recommend this if proper safety steps are taken.

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Check your anti-siphon valve at the fuel tank outlet. Had a chunk of glass mat in one on a Sea Ray with your engine which showed up whenever it felt like it. Same issues as yours.

W

The anti-siphon valve

The anti-siphon valve installed at the fuel tank outlet fitting is a spring loaded ball poppet valve that prevents the contents of the fuel tank from siphoning into the bilge in the event of say a fuel line failure. In order for the valve to open allowing fuel flow, the fuel pump needs to exert a negative suction pressure. Failure of the pump to establish this vacuum condition will cause the type of situation you described. Also make sure the separator/fuel filter and fuel line fittings are tight as it is in the pump suction and could be leaking air. Before cranking, leave the key in the on position for several seconds in order for the fuel pump a chance to prime and fully pressurize the fuel rail. The fuel pressure regulator (a separate element on MPFI) may also be leaking down when the engine is shut off. A fuel pressure check at the fuel rail will confim this and aid with finding the problem.

Thank you Wingnut,

I did check the anti-siphonig valve two days ago, it was working properly; it was free of any dirt or obstructions and the spring inside was of the proper tension, it was allowing the full flow with a discrete amount of vacum in one direction, wile it was blocking the flow in the opposit direction fully. Wile i did this I also checked the fuel line to water separator for clogging or other possible problems that too was in good working order and the water separator was clean of any water or dirt and it was full with gasoline when I removed it from is seatand very thight. That all section of the fuel system looked Ok

Today I will be concetrating on the batteries I will test them with a heavy duty battery tester (resistor type). I should be able to see

how the batteries behave under direct load; if they mantain proper voltage or if they drop below 12,5 volts which according to all consenses will compromise the ECM electric feed and funtionality.

I will let you guys know>

Thanks again and Ciao for now

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Thank you Wingnut,

I did check the anti-siphonig valve two days ago, it was working properly; it was free of any dirt or obstructions and the spring inside was of the proper tension, it was allowing the full flow with a discrete amount of vacum in one direction, wile it was blocking the flow in the opposit direction fully. Wile i did this I also checked the fuel line to water separator for clogging or other possible problems that too was in good working order and the water separator was clean of any water or dirt and it was full with gasoline when I removed it from is seatand very thight. That all section of the fuel system looked Ok

Today I will be concetrating on the batteries I will test them with a heavy duty battery tester (resistor type). I should be able to see

how the batteries behave under direct load; if they mantain proper voltage or if they drop below 12,5 volts which according to all consenses will compromise the ECM electric feed and funtionality.

I will let you guys know>

Thanks again and Ciao for now

You might want to hook a fuel pressure gauge to the fuel rail shrader fitting and take a high speed ride, while looking for a drop off in delivery pressure. Good luck. I had a strange issue with a Volvo ECM and a set of deep cycle batteries.

Old Post...

Picky ECM on Deep Cycle Batteries

The Volvo ECM has a rectifier bridge with series triacs which fire in unison when establishing their bias. As a result, this momentary amperage demand will draw the line voltage down significantly enough when the system is running off the alternator to set a fault, and then all manners of craziness begin. We stumbled upon this by accident when dealers started installing twin deep cycle batteries, in lieu of a deep cycle for battery #2 and a conventional starting battery for battery #1. If an owner started on battery 1 and quickly switched to battery 2, when the ECM went to open loop operation after warm up the momentary spike would look to the battery to have adequate amperage to service the high amperage spike and maintain a minimum line voltage of 13.5 VDC. As the alternator was only supplying 13.8 VDC at idle, the line voltage would drop to the mid 12's for a few seconds, and then all kinks of crap would begin to happen. Volvo actually has a bulletin out referencing the need for a starting battery to service the ECM, and the importance of using hex nuts instead if wing nuts on battery post to ensure they stay tight.

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Thanks Wingnut, my engine is a Mercruiser 5.0 EFI and my outdrive a Bravo III, but I beleve that somewhat your input is right on target, and so was WhiteCap II in fact I am very happy to report that my boat is working right again and the engine is back to tune and the problem gone!.

Yesterday, when I checked the batteries, #2 was totally shot ( the tester showed "FAIL") and battery #1 showed at 75%.

I think that although the batteries were in such bad shape I was getting my good Starting because of the Shore Charger power, but then when on the Move the full demand for electrical energy power, including the load of all the accessories on, mercathode system, radios, etcetera, was resting just on the alternator shoulders , and when periodically the compressor of my refrigerator would kick in, then the electrical drown was so high the the voltage probably dropped even below 12 Volts and that must compromise the electrical supply to the ECM and create my erratic problem, later when the compressor was off again then i would regain some voltage back and I was able to regain some power to ECM and restart the engine.

Yesterday I installed the new Battery #2 and I also turn off my refrigerator and the engine ran with no problems the all day.

I try to recreate the possible condions like when I had the problem: I ran the engine in all speed ranges, made all sorts of crazy turns; left, righ and full figure 8 , even jump over my own wake to simulate rough conditions that coud have possibly have triggered faults at potential loose electrical connections or even get potential dirt or muk to be taken from the bottom of fuel take, but the engine ran well and never quit once and it only shot off when I turn the key to off back at the dock.

So guys it looks like WE GOT IT! WE fix the problem! and I have you fellows and this blog to thank for it.

Thank you for all for your help and the input of your wisdom and experience I really appriciate it, and you all got my gratitude and respect.

PS. Now, it sounds like the gimble bearing has a louder voice; it grouls a little, expecially on the turns. I am going to grease it up again but I'm not to confident about the outcome and I think that this is going to be our next topic :0).

Ciao everyone, thanks again and Happy boating to you all.

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great to hear a happy ending! I was searching Fuel pressure for my EFI and came across your story.

I hope I have the same luck soon. I've had the Marina in Playa Blanca farting around with our boat for a year now and she just wont get on the plane now (used to) and at WOT she lugs, smells of fuel (like the choke was out) but lacks power above about 2000 rpm.

Engine is sweet at low revs and have checked all usuals like compression (great), plugs (new), batteries (new).

My Merc dealer in UK (but boat is in Canaries 1500 miles away) said first check the fuel pressure ! That will be the next job if I can find a man that can? Experts out there are few and far between.

Wish us luck. This is driving us crazy as its a long way to go to a boat you cant trust to take too far anymore. Nick

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Wingnut

Does nickbailey have any diagnostics to connect to ? If yes. I would recommend he buy his own code reader to get into the right areas. Not cheap . But no other alternative.

Just saw the last date of the original posting. :) Double :)

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The problem has coming back regularly I thought it was fixed but it was just a coincidence an longer period of time before eventually it show up again and it has driven me nuts! But now after three years I figure out my problem and I even got to fix it!!and this time for GOOD!! But in order to do that I had to fully empty the gas tank and look inside with the aid of a small video camera. When I inspected the tank I found a brown, thick and strong 15 sq.in. piece of wrapping paper. I pulled it out by using a vacuum cleaner, which I had to modified for the occasion and now my problem is solved and I have not being having any issues for since April 2015 and I have being running the boat almost every day for more then 90 hrs. Here is my theory: The paper was floating around at the bottom of the tank and every once in while it would end up right under the gas pickup inlet and the suction from the electric pump would pull it up blocking the hole and the gas flow of gas to fuel system. In fact at that point the only gas that would find his way to throttle body was that that was allowed to flow true 2 little V shaped notches that were cut and present at the bottom of the inlet gas pick-up tube. Logically this explains exactly the sequence of the events and the way the problem present it self: the boat will cutoff for luck of fuel and the minimal amount of fuel let in by the 2 notches was just enough for the engine to run at idle speed. It even explains the fact that the next day the boat would run fine because when overnight the vacuum, normally generated by the electric pump, would drop to zero it would allow the piece of paper to drop back to the bottom of the tank and move away from under the fuel pickup tube and later reestablish a perfect gas flow at least until some time later when the process would repeat itself. I still do not know how this piece of paper find its way into my gas tank but I can tell you that as result of that I have now moved to another marina and the mechanics from of my old marina never got a dime from me. I am trying to post a picture of the piece of brown thick paper so that I can show it and point out some peculiar characteristic on it.

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The problem has coming back regularly I thought it was fixed but it was just a longer strick that i whent without problems but eventually it did happen again and from time to time has driven me nuts! but now After three years I figure out my problem and I even got to fix it!! This time for real!!!!! But in order to do that I had to fully empty the gas tank and with the aid of a video camera inspect the same and when I found a brown thick 15 sq.in. peace of wrapping paper. I pulled it out by using a vacuum cleaner which I had to modified for the occasion. The paper floating around the tank every once in while would end up right under the gas pickup inlet and the suction from the electric would pull it up blocking the gas flow of gas to fuel system. In fact at that point the only gas that would find his way to throttle body was that that was allowed to flow from 2 little V shaped notches that were cut at the bottom of the inlet gas pick-up tube. Logically this explains exactly the sequence of the events and the way the problem present it self. It Even explains the fact that the next day the boat would run fine because when overnight the vacuum from the electric pump would drop to zero it would allow the piece of paper to drop back to the bottom of the tank and move away from under the fuel pipe inlet and later reestablish a perfect the gas flow at least until some time later when the process would repeat itself. I still do not know how this piece of paper find its way into my gas tank , but I can tell you that as result of that I have now moved to another marina. I am trying to post a picture of the piece of brown thick paper so that I can show it and point out some peculiar characteristic on it.

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The problem has coming back regularly I thought it was fixed but it was just a longer strick that i whent without problems but eventually it did happen again and from time to time has driven me nuts! but now After three years I figure out my problem and I even got to fix it!! This time for real!!!!! But in order to do that I had to fully empty the gas tank and with the aid of a video camera inspect the same and when I found a brown thick 15 sq.in. peace of wrapping paper. I pulled it out by using a vacuum cleaner which I had to modified for the occasion. The paper floating around the tank every once in while would end up right under the gas pickup inlet and the suction from the electric would pull it up blocking the gas flow of gas to fuel system. In fact at that point the only gas that would find his way to throttle body was that that was allowed to flow from 2 little V shaped notches that were cut at the bottom of the inlet gas pick-up tube. Logically this explains exactly the sequence of the events and the way the problem present it self. It Even explains the fact that the next day the boat would run fine because when overnight the vacuum from the electric pump would drop to zero it would allow the piece of paper to drop back to the bottom of the tank and move away from under the fuel pipe inlet and later reestablish a perfect the gas flow at least until some time later when the process would repeat itself. I still do not know how this piece of paper find its way into my gas tank , but I can tell you that as result of that I have now moved to another marina. I am trying to post a picture of the piece of brown thick paper so that I can show it and point out some peculiar characteristic on it.

Wow, glad you figured it out and posted the solution!

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