Boat shifts and revs but doesn't accelerate?

[iluther]

I have a 1986 140hp mercruiser and boat was working fine but now it will shift into gear and push the boat at idle but when you throttle up the engine revs but the boat goes no faster. I checked to see if the propeller is spun It does turn on the hub but it takes a lot of pressure and in gear the spline that the propeller goes on does not turn so I am at a loss. Also the drive shaft does move faster when the engine revs and the gears in the upper unit look good. And the propeller moves faster when out of the water on ear muffs. Any help would be greatly appreciated! Thanks!

 

[Scout Sport Fish]

Re: Boat shifts and revs but doesn't accelerate?

...what?

Very odd.

Does the engine seem to run ok? Just you dont move and it revs up pretty high?

 

[ondarvr]

Re: Boat shifts and revs but doesn't accelerate?

Welcome to iboats.

It sounds like a spun hub, it would need to be falling apart befor you would to be able to turn it by hand. Mark the prop and the hub before putting it in the water then check after you take it out, if the marks don't line up it's spun.

 

[iluther]

Re: Boat shifts and revs but doesn't accelerate?

The engine runs great and it shifts in and out of gear smoothly. The prop just doesnt seem to go faster than idle. Also it seems to want to start going faster if I throttle up slowly but then right away goes back to idle and if I continue to idle in gear for a while it seems to go slower and slower

 

[Chris Hyde]

Re: Boat shifts and revs but doesn't accelerate?

Definitely a spun prop.

 

[danond]

Re: Boat shifts and revs but doesn't accelerate?

iluther: turn the engine off, shift the drive into gear, get out and try to turn the propeller. If it turns and the internal hub stays put, take the prop off and bring it to a propeller shop for a rebuild.

 

[KMaher]

Re: Boat shifts and revs but doesn't accelerate?

72 Reinell, 350, omc everything has been rebuilt,
runs great sounds great, but doesn't go any faster than about 8mph. 9 with a tail wind LOL.

 

[Wayne R]

Re: Boat shifts and revs but doesn't accelerate?

I saw that some one said that you shouldn't be able to spin the prop by hand is that true, because I can spin the prop on my boat? The problem I'm having with my boat is that it runs great but I can't get get it to go faster than 20 miles per hour, it has a chrysler V8 with an Volvo Penta 270 outdrive. Any suggestions to get it o go faster would be outstanding.

 

[ondarvr]

Re: Boat shifts and revs but doesn't accelerate?

Wayne R

When checking for a spun hub when the motor is in gear, normally you still can't turn it (get it to spin on the hub) by hand, if you can the prop is very bad. We're not talking about having it in neutral, it should turn (with the hub) then.

 

[chiefalen]

Re: Boat shifts and revs but doesn't accelerate?

If your not overheating than it's the prop.

Buy a new one and fix the old one and keep it as a spare.

I always carry a spare with me.

 

[runbwood]

Re: Boat shifts and revs but doesn't accelerate?

iluther: turn the engine off, shift the drive into gear, get out and try to turn the propeller. If it turns and the internal hub stays put, take the prop off and bring it to a propeller shop for a rebuild.

I had the same issue. Did exactly what you suggested, saw the prop turning, but not the center hub. Changed out prop and I am back to moving. Thank you!