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Transmission slips?

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etsah57

New member
Mustang 38' with twin 454 Mercruisers. 1 unit operates perfectly, the other is great until it gets to just over 3,000rpm, then it appears to loose drive connection between the engine and prop as the engine suddenly has no load and revs to max. Quickly dropping the throttle back low then seems to reconnect the drive and we can slowly increase the rpm again. Keeping it under 3,000 rpm and we have no problem. Can anyone tell me what might be causing this problem?
 
Ya more info needed. Could be a few things. Engine coupler, prop hub if applicable, I'm thinking this may be a Bravo and suspect clutch too.
 
Will pull the boat out of the water next week. The boat only has 530hrs on it. Looking through the manual I am suspecting it might be the flo torq drive hub behind the prop. Any thoughts?
 
Ok, Will do. But why is everything fine up till about 3,200rpm, then the engine suddenly looses the load and revs its head off. Bring the throttle back down, load comes back onto the engine and we go cruising again. No problems if we keep that engine under 3,000rpm. The other engine is fine, no problems even at full throttle. It's a new problem that has suddenly developed.
 
You could draw a line thru the prop and run it and if the line doesn;t match up then it's the prop.

If the motor overheats, and the drive is a alpha with the impeller in the drive it's the coupler.

A bravo will have the raw water pump mounted on the engine with a belt.

See why when you post a question you need to give us that vital info. not what boat you have but what motor and drive. In your case we need to know the drive.

In a nutshell alpha drive impeller in the drive and it starts to slip does that motor start to overheat, if yes the coupler of no the prop.

You could throw on a spare prop, you do carry one don't you on the boat?

My opinion your prop spun, cause you didn't say you smelled rubber burning in your bilge.

By the way you don't have to pull the boat out to change a prop.
 
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We didn't have any overheating because as soon as it slipped we slowed the motor , it reengaged and then ran it up again to over 3,000rpm, slippage/overreving happened, slowed it down until reengaged and then kept the revs under 2,500rpm, no overheating or dramas.
All too quick to notice any burning rubber.
Don't know if there is a spare prop. My brother just bought the boat.
What is the best way to quickly tell if the sterndrive is an Alpha or Bravo type? I won't be back to the boat until next week when we pull it out of the water. It would be good to have a few clues to what I am looking for. I have zero experience with Mercruiser. Have worked on Tug boats and prawning trawlers. Been an Automotive mechanic for almost 40 years.
 
etsah57 said:
We didn't have any overheating because as soon as it slipped we slowed the motor , it reengaged and then ran it up again to over 3,000rpm, slippage/overreving happened, slowed it down until reengaged and then kept the revs under 2,500rpm, no overheating or dramas.
All too quick to notice any burning rubber.
Don't know if there is a spare prop. My brother just bought the boat.
What is the best way to quickly tell if the sterndrive is an Alpha or Bravo type? I won't be back to the boat until next week when we pull it out of the water. It would be good to have a few clues to what I am looking for. I have zero experience with Mercruiser. Have worked on Tug boats and prawning trawlers. Been an Automotive mechanic for almost 40 years.
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If you can run up to 3000 rpms or so and then the rpm's jump and it feels like you are spinning your wheels on the ice and the boat slows down then you lower your rpm's and do it all over again, Your propellers are in need of service because they are cavitating.
 
when i spun my prop i was good to about 2000.

look in the engine bay, starboard side if there is a pump with water hose going in and out run bye a belt it's a bravo.

Maybe you hit something like doc thinks and the props are all f---ed up.
 
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