1993 mercruiser 4.3lx dies after a few minutes

[Kjohn223]

Hi, this is my first post and I’m having serious trouble with my 1993 Baja 180 islander with the mercruiser 4.3lx. It has a 4bbl carburetor. Here’s my problem, the engine starts up great and runs fine out of the water. When I put it in the water, i can cruise out and get on plane no problem, engine runs great and will go WOT. However, after about 2-3 minutes of cruising at 3200 RPM, the engine will start to surge and eventually it will quickly die out unless I reduce throttle. The engine will continue to idle and will run up to about 2200 RPM. However, as soon as I get past this certain point with the throttle, the motor completely dies, and it is a struggle to get back started. Once running again, I am able to limp back to the dock and get back out of the water. My question is, what is causing my boat to behave like it is running out of fuel? I replaced the water separator, fuel pump. But here’s the kicker, after replacing the fuel pump, the engine ran fantastic again and acted like it had no problems, so I assumed all was fixed. I tried going out again today and I had the same exact problem, the engine acted as it did before I replaced the fuel pump. If anyone could please give me some advice I would appreciate it.

 

[Scott Danforth]

your running out of fuel

check your fuel pressure you most likely have a restriction before the pump

could be plugged anti siphon valve
could be debris in the pickup tube
could be plugged tank vent

always test and diagnose prior to replacing parts.

 

[Eric 3.7LX Alpha 1]

What he said ^^^^^^^

 

[Bt Doctur]

And could also be a filter inside the pickup tube

 

[Kjohn223]

Just took the floor off and pulled the fuel pickup out, it is spotless and clean. What else could be causing this problem? I'm thinking I got bad gas with water in it from the gas station... Would water in the gas cause these symptoms? If not, what else could be the cause.

 

[nola mike]

Just took the floor off and pulled the fuel pickup out, it is spotless and clean. What else could be causing this problem? I'm thinking I got bad gas with water in it from the gas station... Would water in the gas cause these symptoms? If not, what else could be the cause.

Yes, that's possible. Did you check the contents of the filter when you changed it? Other causes already listed in post #2

 

[Kjohn223]

Yes, that's possible. Did you check the contents of the filter when you changed it? Other causes already listed in post #2

yeah I poured the water seperator into a clear cup and couldnt see any water in it, but since it sat all winter with ethanol fuel, I'm suspicious... I'll also check the other items listed.

 

[Scott06]

Just took the floor off and pulled the fuel pickup out, it is spotless and clean. What else could be causing this problem? I'm thinking I got bad gas with water in it from the gas station... Would water in the gas cause these symptoms? If not, what else could be the cause.

see post #2 Have you checked th otheritems on the list

rule fuel pressure out by measuring it.

Have you checked spark when it dies ?

 

[poconojoe]

Is there a filter stone or strainer at the carb fuel inlet? That could also be clogging up.

If there's no clog in the fuel lines and components, couldn't the carb have some blockage or problems with the float or it's needle?

 

[Kjohn223]

after siphoning all the gas out and taking apart the anti siphon valve that’s connected to the fuel pickup, and the anti drain back valve works fine. The only thing left would be the carburetor. Not sure what’s wrong with the carburetor, I don’t have much experience with big carburetors, just dirtbikes.