4.3L stalling after running fine for 30 minutes

[ajnader]

I have a 2002 Searay with twins 4.3L. When you start both engines they run perfect, after running them at about 4000 RPM for 30 minutes the rpm's on the port side engine star to drop to 2500-3000 and keep going up and down. If I pull down the throtle and bring the RPMs down to 3000 the engine works fine and after a couple of minutes I can bring it up to 4000 again with no problem. Also, if I stop the engine for a couple of minutes the problem goes away but after a few minutes the engine start with the same problem.
Do you think it may be a fuel filter problem or an ignition problem.
The engine starts on the first crank and idles perfect.
Any suggestions?

Thanks in advance.

 

[imported_TheMan]

Re: 4.3L stalling after running fine for 30 minutes

If it is running fine for 30 minutes you probably have a faulty ignition system. A fuel supply problem would probably render itself long before hand, whether on the supply side or filter side. I suppose it is possible you could be boiling fuel out of the carb at higher RPM, but I think that is pretty unlikely especially since it comes and goes.

I would personally try to inspect the coil and distributor. If it were my boat I would switch ignition coils between and engines and see if that causes the problem to shift engines. Then you can replace the faulty coil if that is indeed the problem.

Welcome to iBoats!

 

[imported_TheMan]

Re: 4.3L stalling after running fine for 30 minutes

Just to add a little more, my own experience involved a faulty coil that failed to provide a charge when it got hot. Ran perfectly for the first 40 minutes, then wouldn't do anything until it cooled off. If yours is malfunctioning it might be providing weak/errant charging conditions.

 

[ajnader]

Re: 4.3L stalling after running fine for 30 minutes

Thanks all of you guys for the advices, I'm going to replace the coil this weekend and test it. Hopefully this will solve my problem, I will let all of you know. I took the boat out last weekend after replacing the fuel filter and it did the same except that it only ran fine for about 10 minutes and then the RPM's started to drop again. I have a question, why at 2800 RPM's or less the engine works fine? Maybe the coil doesn't get hot at low RPM's?
Thanks again for your help.

 

[Don S]

Re: 4.3L stalling after running fine for 30 minutes

You may also have a fuel delivery problem on that engine, instead of an electrical problem. Read this thread.

http://forums.iboats.com/showthread.php?t=167561

 

[imported_TheMan]

Re: 4.3L stalling after running fine for 30 minutes

I was recommending switching coils between engines to try and prevent replacing parts without knowing if they are good/bad.. But if you got the cash or are confident enough from our opinions, I hope it works!

To anyone else: Since it's the Thunderbolt ignition (non points)that eliminates several other problems, right?

Don, if you get a chance could you explain why/how it would be an intermittent fuel problem to me? Just trying to learn as much as I can..

At 4000 RPM for 30 minutes, what type of fuel problem would show up and then go away after you idle down and re-appear when you throttle back up?

 

[ajnader]

Re: 4.3L stalling after running fine for 30 minutes

Yesterday I was installing my new coil and the negative electric connector broke. I replaced with some spare connectors I had in my tool box and finished the job( I will test the boat this weekend and will let everybody know how it works). I noticed the connector that broke was long and covered with black rubber, I replaced it with a regular electric connector(round eye type), can this cause any problem? If yes, where can I buy this long insulated electric connectors?
Thanks

 

[imported_TheMan]

Re: 4.3L stalling after running fine for 30 minutes

You shouldn't have any problems based on that connection. Additional insulation/tape/etc is just to protect the wires... either from chafing or atmosphere or to protect users

Keep us updated.

 

[ajnader]

Re: 4.3L stalling after running fine for 30 minutes

OK guys need more help. Took the boat yesterday for a ride. The first 10 minutes the boat ran perfect, both engines at 4000 RPM, after 10 minutes the same engine started stalling and I had to bring it down to 3000 RPM. I made to my destiantion with one engine at full throtle and the other one at only 3000 RPM. On my way back got worst, again both engine ran perfect for 5 minutes and then the same engine start it again but this time I could not take it over 1800 RPM, so basically I came back with one engine. I already replaced full filters on both engines and the ignition coil on the engine with problems. What else should I check?
I notice the battery gauge on the engine with the problem only marks 12 and the other engine is always at 14 volts. Would a bad alternator cause a problem like this?
Also, if when the engine start stalling I don't bring the throtle back you start smelling gasoline.

Thanks

 

[Bondo]

Re: 4.3L stalling after running fine for 30 minutes

At 4000 RPM for 30 minutes, what type of fuel problem would show up and then go away after you idle down and re-appear when you throttle back up?

Ayuh,.....

Crap floating around in the fuel tank,..?? Clogged tank Vent,..??

I notice the battery gauge on the engine with the problem only marks 12 and the other engine is always at 14 volts. Also, if when the engine start stalling I don't bring the throtle back you start smelling gasoline.

Ayuh,....

Did you click on,+ read this link Don left for you,....
You Should,.... It'll probably lead you to the root of your Issue.....

You have an electric fuelpump,.... I'd probably start There from your description.....

 

[ajnader]

Re: 4.3L stalling after running fine for 30 minutes

OK guys, after replacing the ignition coil, alternator,2 water separators and 2 batteries, I finally found the problem: it was the in line fuel filter between the tank and the fuel pump. I didn't know these engines had these filters. I still have a question, why my engines don't have the fuel cooler system as it shows on the parts book? my engines only have a shut off solenoid, an in line fuel filter, the fuel pump and the water separators,is this normal?

Thanks

 

[Don S]

Re: 4.3L stalling after running fine for 30 minutes

What is the Mercruiser SN for your engine?

 

[ajnader]

Re: 4.3L stalling after running fine for 30 minutes

serial number is 0M092192 and I did find it also has a fuel cooler system with another fuel pump, so these engines have 2 pumps?

Thanks