Volvo penta revs up no go?

[kinger87]

HI, I'm new here and bought a boat last august, its relatively old, but in good shape, I figured I can fix just about anything so yea..lol.

Its a 82 Bayliner equipped with the volvo penta aq120b motor and 270 outdrive. I used in for a couple months last summer with no problems. I changed the outdrive oil and engine oil before parking it for the winter.

I had the outdrive slightly overfilled, that is corrected now. but the issue that has started this year is as soon as you get to about 3000 rpm's and try to get it to plane out and start moving, the motor just kinda "free revs" and you get very little additional forward movement. low speeds it works great. The engine sounds healthy, I replaced the oil points with a pertronix setup..etc. Am I missing some additive in the oil thats not allowing it go?? or is there something mechanical shot, like maybe clutch cones or something?? thanks for any assistance.

 

[Phantom_II]

Re: Volvo penta revs up no go?

Sounds like a spun prop hub or cavitation.
Are your prop blades in good shape?

 

[kinger87]

Re: Volvo penta revs up no go?

yea the prop is in great shape, I chewed it up a little last year, but got it all repaired with no problems. (paid the 30 bucks for the good launch now..lol) I actually have 2 of them, both are good. It feels really odd, but no matter how much you fiddle with the throttle it just will not go fast. I guess the proper way to explain it would be like a clutch slipping, but without the clutch .. lol.

 

[Fun Times]

Re: Volvo penta revs up no go?

Put the drive in a gear of you choise with the engine off and on the trailer then try turning the prop with little pressure till it locks up one way [and it might not lock up the other way yet not 100% sure of that right now] But once it's locked up put some pressure to it and see if it will turn it should not turn and if it dose then try to watch the shaft if it dose not turn and the prop dose then you have a spun hub in the prop, If the shaft turns the something might be wrong inside the drive, also try putting it in the other gear and spin it to see if it locks up or not.

 

[bruceb58]

Re: Volvo penta revs up no go?

Is a Volvo so it has to lock up...cone clutch.

You will not be able to hand test the prop out of the water. Even standing on it won't be much help since your problem is at 3000 RPM and there is much more force being applied than you can do.

Mark the prop and the hub and see if it slips or not when you take it out next.

 

[kinger87]

Re: Volvo penta revs up no go?

ok I will do that today, and post back. but out of curiosity what usually goes bad most often that would cause this? The thing was treated relatively well over the years, and I believe just standard wear items would be goin, but I would expect nothing less on something that is over 25 years old. thanks for the help so far,

Mark the prop and the hub and see if it slips or not when you take it out next.

by that you mean the splines that the propeller attaches to correct?

 

[bruceb58]

Re: Volvo penta revs up no go?

The hub is the center section of the prop that contains the splines. That whole assembly is pressed into the prop and it is that interface...between the prop and the hub that may slip. They are designed to slip in case you hit something. In your case that may be your problem...let's hope!

If you have a spare prop, put it on!

 

[kinger87]

Re: Volvo penta revs up no go?

YES!! this was the problem, I put my spare prop on and took her on a little beat run today, running perfect, planes right out, hammer on it for the hole-shot and its good to go!

On a side note anybody have a lead on another used prop so I have a spare? 14 R 17 is what it says on the side of the prop...

 

[tbear1964]

Re: Volvo penta revs up no go?

Your prop shop can redo your hub.

 

[bruceb58]

Re: Volvo penta revs up no go?

Your prop shop can redo your hub.

I second this.

You can also buy one on Ebay but just be aware that you could get one with a bad hub as well. Best to get the one you have repaired