1991 MerCruiser 350: Fuel Problem?

[remmi002]

I have a 1991 MerCruiser 350 in a 21' Ski Supreme, engine ran excellent when out last week. Went out last night, started hard (first time ever), but eventually did start. There was moisture over the engine, including the disturbitor as we have had some heavy rainfall over the last few days and my cover is not in the best condition. Engine would sound like it was starving when attempting to accelerate. Would run decent/not great when more of a constant (non-accelarating fuel was applied), but would basically kill whenever acceleration was attempted. Puilled plugs and rechecked gapping all were good, but one, reggapped it. Attempted to drive again and with a slow really easy going accelration got up to top end and cruised fine. When slowed and attempted to accelerate hard it would starve again, and it sounded as if it was backfiring through the carb. Not sure what the problem could be, my guesses are either fuel pump or maybe distributor point gapping??? Please let me know what you think, I surely appreciate all advice, and have a good weekend. Hopefully I will get her up and running for it as well!

 

[Haut Medoc]

Re: 1991 MerCruiser 350: Fuel Problem?

Welcome to iboats.......
Remove the distributer cap & look for moisture.....
Change the water separating fuel filter.....​

 

[Chris1956]

Re: 1991 MerCruiser 350: Fuel Problem?

Remmi, that motor should have an electronic ignition, w/o points. I would check the coil tower for arcing, and if the cap. rotor and wires have not been changed in a few years, this would be a good time.

I had a similar incident where the ocean was rought enough to toss salt water up on top of the motor. The coil and dist cap started arcing over. I replaced the cap, rotor and wires and the motor ran 100% better than it did before the salt water incident.

 

[remmi002]

Re: 1991 MerCruiser 350: Fuel Problem?

I believe it does have points, distributor points? As when I first bought the boat about two months ago it ran rough, so the seller had them regapped by his marine mechanic before payment. This in turn caused it to run flawless up till this point.

 

[Haut Medoc]

Re: 1991 MerCruiser 350: Fuel Problem?

I really doubt that you have points on that late of a model......
Pull the cap & look for moisture....
Or just replace cap & rotor if they are a few years old....
There are really only three things that will cause backfire through the carb.....
Lean condition, which can be caused by water in fuel....
Incorrect ignition....Caused by crossed plug wires or tracking from excessive moisture in dist cap, or....
Defective or tuliped intake valve....
Take your pick......​

 

[remmi002]

Re: 1991 MerCruiser 350: Fuel Problem?

I just checked it out, it appears as if there is not an electronic ignition, in fact does have point. I am in the process of getting a new fuel filter at this time? Any other suggestions?

 

[Haut Medoc]

Re: 1991 MerCruiser 350: Fuel Problem?

Points....Surprising.....
No moisture in the cap?.....
What is the condition of the points?....
Get a timing light that can detect advance.....
You might have sticky advance weights from the rain & moisture....​

 

[Windykid]

Re: 1991 MerCruiser 350: Fuel Problem?

Clean the points plate with emery cloth. Replace and regap points and condenser.

Replace cap and rotor.

replace fuel water separator.

If the problem still exist, probably coil.

 

[remmi002]

Re: 1991 MerCruiser 350: Fuel Problem?

The engine model is a 350 c.i. MerCruiser "Ski" (260 hp), apparently the only non-electronic ignition of that year, it is also sea-cooled as well. Will check the cap and what not when I return home from work. Thank you for all the good advice, I'll let you know what I find.

 

[remmi002]

Re: 1991 MerCruiser 350: Fuel Problem?

Aother question of the sort, is now a decent time to just dive in and install an electronic ignition conversion. Rather than just replacing the points and the condensor? What are your opinions on an electronic ignition? Is it the best route to go, or just repair what I have?

 

[Haut Medoc]

Re: 1991 MerCruiser 350: Fuel Problem?

You could, but I would figure out what is wrong before I would start throwing other parts at it....
Some swear by the Pertronix....
I personally think points are a time tested method & not really a pain....​

 

[dpmdwm]

Re: 1991 MerCruiser 350: Fuel Problem?

I have a 1991 MerCruiser 350 in a 21' Ski Supreme, engine ran excellent when out last week. Went out last night, started hard (first time ever), but eventually did start. There was moisture over the engine, including the disturbitor as we have had some heavy rainfall over the last few days and my cover is not in the best condition. Engine would sound like it was starving when attempting to accelerate. Would run decent/not great when more of a constant (non-accelarating fuel was applied), but would basically kill whenever acceleration was attempted. Puilled plugs and rechecked gapping all were good, but one, reggapped it. Attempted to drive again and with a slow really easy going accelration got up to top end and cruised fine. When slowed and attempted to accelerate hard it would starve again, and it sounded as if it was backfiring through the carb. Not sure what the problem could be, my guesses are either fuel pump or maybe distributor point gapping??? Please let me know what you think, I surely appreciate all advice, and have a good weekend. Hopefully I will get her up and running for it as well!

HI THERE REMMI02 - did you ever fix this problem?
I have a 1983 Ski Supreme with a Ford PMC 351/4 in it - same issue. I can start and run for a short time. Tow a skier or tuber for maybe 15 minutes. BUT - once I have run for a short time and cannot throttle up anymore. It stalls on acceleration and is difficult to restart. Time heals the problem, but it always comes back when run.