Engine revs out once it hits 3000rpm

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Skybreeze

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I have a volvo penta DPA powered by a 431a engine. Went to get up on the plane and all seems fine untill I hit 3000 rpm and its like its a spun prop and lets go. The engine revs out and the boat goes nowhere. It goes into gear fine and runs along fine under 3000rpm. As soon as I hit 3000 it just revs out. Took the props off to check but I have solid aluminium props so no facility for them to fail. Can anyone point me in the right direction of where the problem is. It doesn't feel like the cone clutch as I have had one of those fail before. From my experience when one of those fails it revs up slightly hire from idle before it engages into gear with a clunk.
 
Bondo

Bondo

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Skybreeze said:
I have a volvo penta DPA powered by a 431a engine. Went to get up on the plane and all seems fine untill I hit 3000 rpm and its like its a spun prop and lets go. The engine revs out and the boat goes nowhere. It goes into gear fine and runs along fine under 3000rpm. As soon as I hit 3000 it just revs out. Took the props off to check but I have solid aluminium props so no facility for them to fail. Can anyone point me in the right direction of where the problem is. It doesn't feel like the cone clutch as I have had one of those fail before. From my experience when one of those fails it revs up slightly hire from idle before it engages into gear with a clunk.
Click to expand...
Ayuh,..... I'd start by checkin' the drive oil for debris,....
Next, I'd be looking at the drive coupler,....
 
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Skybreeze

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Bondo said:
Ayuh,..... I'd start by checkin' the drive oil for debris,....
Next, I'd be looking at the drive coupler,....
Click to expand...
I was thinking coupler but will check drive oil first. What should I be looking for in particular.
 
Bondo

Bondo

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Ayuh,....... Anything other than oil,....
 
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Skybreeze

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Bondo said:
Ayuh,....... Anything other than oil,....
Click to expand...
Finally got onto draining the oil
There was a little water that came out first.
Then a little milky
Followed by what appeared good oil.
No sign of any debris.
Not sure next move but was thinking fill with new oil and test run.
I guess the only 2 things it could be is cone clutch or drive damper.
My experience with a failed cone clutch before is when engaging forward the engine revs a bit and then engages with a clunk.
This isn't doing that at all.
It engages nicely and accelerates but when it hits around 3000rpm the engine revs out like a clutch plate in a car slipping. When I decelerate the drive takes up again but never sounds as though it comes out and back into gear. It just slips then doesn't.
Do you think this points towards drive damper or can the cone clutch do that as well. I have only had the one experience with a failed cone clutch and that was due to hitting something in the water with the props which caused the clutch to let go. After that it always revved a bit before engaging.
 
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Skybreeze

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Jul 14, 2010
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Put fresh oil in the leg and took the boat for a run out the lake.
It runs fine now.
Conclusion: It had the wrong grade oil in it.
Milk grade doesn't work very well.
Have to change the oil a bit more regularly. I've become a bit slack with servicing as the years have gone by.
 
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