Mercruiser 5.0 L stalling at 1200 rpm

Hi I have a 1994 SeaRay Sundancer 230, with a 5.0 L Mercruiser engine (carburetor) and I have a problem. When I start the boat and slowly accelerate to 1200 rpm, it cuts out completely and stalls. If I throttle up quickly, I can get it past 1200 rpm up to its max, about 3200 rpm. As I throttle down, the engine slows until it gets to about 1200 rpm and then it cuts out and stalls again. I'm able to restart it immediately, sometimes needing a little throttle. This has happened while in gear on my way home yesterday, as well as today (never left marina). Also happens when using throttle only. I have tried adding some fuel injector/high octane cleaner. I have also tried spraying the linkage and the throat of the carburetor w carb cleaner.

Thanks for your help-

JM

Re: Mercruiser 5.0 L stalling at 1200 rpm

My initial thought is the carb. 1200 RPM is about where the carb changes from the primary jets to the secondary jets. There could also be a vacuum leak causing a lean issue. Your boats WOT is between 4400 and 4800 and if it is only getting 3200 ROM I will suggest you do a compression test.

Re: Mercruiser 5.0 L stalling at 1200 rpm

AllDodge said:

My initial thought is the carb. 1200 RPM is about where the carb changes from the primary jets to the secondary jets. There could also be a vacuum leak causing a lean issue. Your boats WOT is between 4400 and 4800 and if it is only getting 3200 ROM I will suggest you do a compression test.

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Thanks, I rarely run it WOT, so I'm really not sure what the WOT max rpm is, when I'm at my normal ideal cruising speed, I'm at 3200 rpm. I've had it tuned up in the spring with new plugs, filters, distributor cap, etc. I'm not sure if they did anything w the carb. Appreciate the thoughts.

Re: Mercruiser 5.0 L stalling at 1200 rpm

I had the same issue on my wellcraft. I used some seafoam in the gas tank and it cleared that problem up. It took three trips to the lake before the hesitation at 1200-1500rpm was gone.

Re: Mercruiser 5.0 L stalling at 1200 rpm

hivoltg said:

I had the same issue on my wellcraft. I used some seafoam in the gas tank and it cleared that problem up. It took three trips to the lake before the hesitation at 1200-1500rpm was gone.

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Before the seafoam, were you able to accelerate past the 1200 rpm "kill zone" if you throttled up quickly? If I go slow on the throttle up or down it cuts out just about every time now. We're you still cutting out after the first time you went out after adding seafoam? Or just hesitating? Thanks-

JM

Re: Mercruiser 5.0 L stalling at 1200 rpm

Jmanteu1 said:

Before the seafoam, were you able to accelerate past the 1200 rpm "kill zone" if you throttled up quickly? If I go slow on the throttle up or down it cuts out just about every time now. We're you still cutting out after the first time you went out after adding seafoam? Or just hesitating? Thanks-

JM

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Yes, I was able to accelerate past 1200rpm if I throttled quickly but I always got that hesitation or I stalled at that rpm. The first time out on the lake after seafoam it still did it but less stalling as the day went on. The second time out it got even better, no stalling, but still some hesitation at 1200-1500. The third time out on the lake the problem had cleared. My tank is 47 gallons and I added a bottle of seafoam. I probably needed two bottles for that much gas but I never tried the stuff before so I didnt want to over do it. Im now using it with every fillup on my boat.