Alpha one drive or I meant "no drive"

[off course]

1999 Mercruiser 5.0L Alpha one drive, lost almost all forward drive with no noise or warning.While using the boat yesterday, it all of a sudden would not gain speed.The engine is fine and it goes into forward and reverse normally with no strange noises, but the boat will not go over 5mph @2400rpm(normally 22-25mph).With the console shifter in forward the prop will rotate forward but not backwards, in reverse it will rotate either direction. I didn't try the boat in reverse after this problem came about,(getting back to land was priority#1). I realize we have an outdrive problem, but before going into the drive are there an tips, test, or tricks to look for.Thanks for the help.

 

[jtybt]

Re: Alpha one drive or I meant "no drive"

Hopefully it's just a spun prop hub.

 

[cr2k]

Re: Alpha one drive or I meant "no drive"

First off check your drive oil and make sure its full and clean. Drain a little and check for metal chunks. If not drive...

2 possibilities come to mind:

1. Spun Prop hub (if older rubber hub type)
Check by painting a line across both the hub and prop center. Run again and see if lines mismatch. If so new prop. If not see #2.

2. Spun coupler (on back of engine). Requires engine removal to replace.
Was there any smoke or burnt rubber smell?

 

[off course]

Re: Alpha one drive or I meant "no drive"

I hoped it was the prop hub, but no such luck.(1st thing I checked).No smoke, smells or noise.

 

[Bondo]

Re: Alpha one drive or I meant "no drive"

.(1st thing I checked).

Ayuh,... How did you check it,..??

 

[off course]

Re: Alpha one drive or I meant "no drive"

Mine is the newer style prop hub w/the black plastic insert on the outdrive side and a splined metal insert on the prop side.I disassembled the prop assembly and examined all the pieces, there is no damage or wear to any of these parts.The splines on the prop shaft, and in the insert all look fine, the plastic insert looks fine as well. The insert still fits the prop good, and all the flats on it have no wear at all. The prop can be rotated forward easily by hand when shifter is in forward, is this correct?

 

[Maclin]

Re: Alpha one drive or I meant "no drive"

Make a mark on the hub and the prop for reference, then run it and see if the marks are still lined up.

 

[off course]

Re: Alpha one drive or I meant "no drive"

Tried the marking thing and the marks were still lined up.What else could it be?

 

[Don S]

Re: Alpha one drive or I meant "no drive"

Look at the coupler. If the rubber part is all lumpy, you spun it. It should be nice and smooth.

 

[Bt Doctur]

Re: Alpha one drive or I meant "no drive"

Check the drive oil level, if none present pull the top cap and look to make sure you dont see this.