Prop / Drive Slipping

[gar2243]

I have a Mercruser 4.3 170 with an Alpha drive 1986
While on the river we hit a object with the prop pretty bad
could back it off quick enough and tore about 2 inches off the
aluminum prop.
I replaced the prop with the old original one, and took it out again
I got about 1/2 mile with good thrust and I heard a high pitch wine
like a clutch slipping rpm's were at 3,500 and boat was slowing down
I was able to get it back to the dock reverse worked forward but when
I give it heavy throttle it slips again.

Where do I start to find out my problem, it seems obvious that it is in the
stern
I am looking for some direction to get started. I bought a manual for the upper and lower unit but not sure what I should be looking for..
Help !

[Tech Support]

If the boat is still working properly at low speed I would suspect the prop hub or the engine coupler. Since the prop was an old one I would suspect that first. Then look at the engine coupler. Normally with the coupler, you smell burning rubber when it fails. It could have also taken out the splines. To check that you need to remove the drive and visually inspect them with a flashlight.

If it does not work at all, then I would suspect something in the drive. You can pop the top cover off and make sure the gears are okay, then seperate the halves and turn the lower driveshaft while shifting the drive to verify the lower is working properly.

Tech Support