Not coming up to full power out of the hole

[Brucebu]

I have a 1988 Malibu Skier, GM 350, "5.7 Ski" with a direct drive Borg Warner Velvet Drive inboard transmission. The boat idles well and revs normal when in neutral but out of the hole to pull a skier it coughs and sputters having trouble going up in RPM. I have replaced the points, condenser, rotor and reset timing to factory spec. I have had the carb. rebuilt, replaced the fuel filters and will replace mechanical fuel pump tomorrow. I will also clean the fuel lines. Some people tell me it is the fuel system. Some say it is the distributor and advise changing to an HEI. I also drained and cleaned the transmission case and filter. Everything on the boat is 21 years old with no problems. I have no problem replacing the parts one at a time as the boat has been bullet proof for 21 years. I just don't know where to go next!
The boat purrs like a kitten in the front yard and I will give it a lake test next week. Any advice where I should go next if the lake test goes bad?
Thanks, Bruce

 

[danond]

Re: Not coming up to full power out of the hole

Suggesting you change to HEI for a hesitation problem is crazy. Don't listen to that guy.

Carbs are frequently rebuilt wrong and then hooked up incorrectly and not adjusted properly. Since it doesn't generally miss/hesitate I'd start with a full carb review and adjustment, including the control/throttle linkage, then check for vacuum leaks (maybe the carb is cracked, intake cracked/leaking, carb to intake seal is on backwards, etc).

It doesn't immediately sound like an ignition system issue.

 

[dontask]

Re: Not coming up to full power out of the hole

I didn't see that you replaced the spark plugs in your list.
I had a Bimini Skier (with a PCM motor) owner come to me with a problem he had been chasing for a while and it turned out to be the oil related safety switch tied into the ignition system control module. It would only allow the engine to stutter at low rpm's.
What rpm's does your engine problem start and how high can you get the rpm's when its happening?

 

[Brucebu]

Re: Not coming up to full power out of the hole

Suggesting you change to HEI for a hesitation problem is crazy. Don't listen to that guy.

Carbs are frequently rebuilt wrong and then hooked up incorrectly and not adjusted properly. Since it doesn't generally miss/hesitate I'd start with a full carb review and adjustment, including the control/throttle linkage, then check for vacuum leaks (maybe the carb is cracked, intake cracked/leaking, carb to intake seal is on backwards, etc).

It doesn't immediately sound like an ignition system issue.

Thanks for the advice against the HEI, that will save me a few bucks. The problem started before the carb rebuild. I did the rebuild to try to solve the problem and won't know if it made a difference until the lake test.

 

[Brucebu]

Re: Not coming up to full power out of the hole

I didn't see that you replaced the spark plugs in your list.
I had a Bimini Skier (with a PCM motor) owner come to me with a problem he had been chasing for a while and it turned out to be the oil related safety switch tied into the ignition system control module. It would only allow the engine to stutter at low rpm's.
What rpm's does your engine problem start and how high can you get the rpm's when its happening?

Thanks, I will replace the spark plugs. I dont think my Mercruiser has the oil related safety switch you mention. Regarding the RPM issue I will check with my son. He had the boat when the problem began. He just described it as not coming up to power when pulling the skier up. It also sputtered and coughed while cruising back to the marina.

 

[buddhapi]

Re: Not coming up to full power out of the hole

pull your distributor cap, and make sure the centrifugal weights are moving freely. this is common with GM distributors. I also agree that double checking your carb for proper tuning may help.

 

[Brucebu]

Re: Not coming up to full power out of the hole

Thanks, I will look in the distributor and try to figure that one out. I just work with points, rotor and condensor!!

A highly recommended mechanic rebuilt the carb. I have to assume it is to factory spec. I would not know any different.

I have been told to use compressed air and blow out the fuel lines from the water separating filter back to the tank. I am assuming this is safe if I remove the filler cap and am careful not to pressurize the tank. Be careful to remove the ball-check valve at the top and only use mild air pressure. I will also clean the fuel tank vent hose as that could be clogged.