please help before I blow up my boat

[ricklaw67]

I have a 1995 Searay with mercruiser 5.7L. Have not have any trouble until this year. Always ran like a top. Back in June i had a tune up done. The engine fires up and runs beautifly "on the trailer". I put it in the water and she runs good for a few minutes and starts stalling skipping ect. Start it up and same thing. It's tough to start back up but it does start up. I put it in neutral and rev her up "Beautiful". put it in gear she either dies or goes but only at idle speed then dies again. bring it out of the water and it runs like a champ again. I did compression test 145-150psi on each cylinder. Changed wires,distrib cap and rotor. dumped out water seperator filter and gas is perfect. It ran perfect when we winterized it last fall. What else could it be?? ignition pick up?? I'm lost and have'nt been able to boat yet this season. I'm going to bring it back to my mechanic but already spent over $2000 this season and im looking to try something myself first.

 

[lowkee]

Re: please help before I blow up my boat

1st thing to check: is the fuel vent host clogged?
2nd thing: adjust the fuel mixture screw out 1/4 turn at a time, as it may be starving for fuel. no load (trailer test) needs little fuel, load (on the water) needs plenty.

 

[Bondo]

Re: please help before I blow up my boat

dumped out water seperator filter and

Ayuh,... There was/ is probably More water in the Carb.....

 

[ricklaw67]

Re: please help before I blow up my boat

First off thank you for the responses!! My mechanic already took the carb off and cleaned it out. I blew on the vent and heard bubbling so i dont think the vent is clogged. What would turning the screw do? it has never been touched and ran fine in the past??

 

[Fishermark]

Re: please help before I blow up my boat

put it in gear she either dies or goes but only at idle speed then dies again.

Do you know what specifically was done in the tune up? I had a similar problem following a tune up last year, turned out to be bad spark plugs. (They were Autolite. I put AC Delco plugs back in and didn't have another problem).

Have someone look and see if the shift interrupt switch is activating when you put it into gear.

If I understand you correctly, when you say you poured out the fuel from the separator, you noticed no water there - correct? The fuel looked good?

 

[Fishermark]

Re: please help before I blow up my boat

What would turning the screw do? it has never been touched and ran fine in the past??

I would not suggest messing with the mixture screw. They don't just go out of adjustment. There are other steps to take first.

 

[ricklaw67]

Re: please help before I blow up my boat

They replaced the plugs when they tuned it up with Champion plugs(junk) but I went and replaced the Champion with NGK last week along with the wires, Cap and rotor. And yes when I looked at the fuel there was no water, scum or odd color it looked good. My mechanic keeps saying it's a fuel problem but I dont know. He told me to bring it in and he will check the disributor pick up??? I'm just trying to see if there is something I can do with out spending another 5oo. Every time it goes in it aleast $350. The biggest problem with checking things is it runs great at home and when I go to the ramp I have to call sea tow for a tow back.

 

[littlebookworm]

Re: please help before I blow up my boat

I'd like to suggest that you check/change the flexible ("rubber") fuel line between the tank and the pump. I've seen a few such lines on cars and boats swell internally because of e10 fuel or age. This cuts off the fuel supply under load when pump suction increases. It's a relatively simple and inexpensive replacement. Just use marine hose rated for e10. Let us know what you find. Hy

 

[ricklaw67]

Re: please help before I blow up my boat

Thank you I will definetly try that and let you know how I make out.

 

[Gary H NC]

Re: please help before I blow up my boat

First off the timing needs checked.Point gap checked and dwell set.
Then the next step i would do is pull the fuel pickup tube out of the tank.
Any signs of fuel in the clear hose from the fuel pump to the carb?

Another easy test is to remove the fuel line from the tank and run the engine off of a portable tank.That will tell you if the pickup tube or anti-siphon valve has a restriction.

If this has the Thunderbolt ignition box make sure it is grounded good to the riser.
I had one doing the exact same thing and it acted like a fuel problem.I chased it for 2 days before i found the ignition box was not getting a good ground at the riser.I ran an extra ground to the block and it has run perfect since.

 

[180shabah]

Re: please help before I blow up my boat

I would not suggest messing with the mixture screw. They don't just go out of adjustment.

...But the mechanic did have the carb apart for "cleaning", probably wasn't in gear, in the water ideling when the mixture and speed were set.

 

[searay3]

Re: please help before I blow up my boat

See if your manual is available at the top of the forum. It has testing procedures for the pickup coil, ign, etc. A multimeter and a free manual are pricesless....

 

[ricklaw67]

Re: please help before I blow up my boat

YEAH IT IS FIXED!!!! The coil had no oil in it. When she heated up it started miss fireing. Replaced the coil and ignition pick up and yeah all better.

Thank you everyone!!!

 

[Fishermark]

Re: please help before I blow up my boat

Glad you got it fixed - and thanks for the update. It can help others when they search for similar issues.