72 85 Johnson slipping gear

[Timok]

Hi everyone, I am enjoying the forums and learning alot. I am hoping I can get some help.
I am having trouble with the bottom end which is an hydro electric drive.
The motor goes into gear both forward and reverse and I can get the boat to plane. But after 10 minutes or so after slowing down or stopping and then trying to get the boat planing again it starts to rev as if it's cavitating. When I pull back the throttle it's still in gear and will move forward albeit slowly.
I have tried a couple of different props,one new, so I don't think the hubs are bad. There are no grinding noises or any banging when I pull back the throttle.
It's the right gear oil (type C) and it's full and clean. I changed the oil after last summer and it was clean then as well. I have spoken to a couple of mechanics around here and none of them know much about the hydro electric drives or want to know. If anybody has any ideas before I take it apart it would be a great help.
Thanks
Tim

 

[F_R]

Re: 72 85 Johnson slipping gear

Hi everyone, I am enjoying the forums and learning alot. I am hoping I can get some help.
I am having trouble with the bottom end which is an hydro electric drive.
The motor goes into gear both forward and reverse and I can get the boat to plane. But after 10 minutes or so after slowing down or stopping and then trying to get the boat planing again it starts to rev as if it's cavitating. When I pull back the throttle it's still in gear and will move forward albeit slowly.
I have tried a couple of different props,one new, so I don't think the hubs are bad. There are no grinding noises or any banging when I pull back the throttle.
It's the right gear oil (type C) and it's full and clean. I changed the oil after last summer and it was clean then as well. I have spoken to a couple of mechanics around here and none of them know much about the hydro electric drives or want to know. If anybody has any ideas before I take it apart it would be a great help.
Thanks
Tim

Don't take it apart. There is nothing inside that can possibly slip without making a heckuva racket and grinding.

 

[tx1961whaler]

Re: 72 85 Johnson slipping gear

Hi everyone, I am enjoying the forums and learning alot. I am hoping I can get some help.
I am having trouble with the bottom end which is an hydro electric drive.
The motor goes into gear both forward and reverse and I can get the boat to plane. But after 10 minutes or so after slowing down or stopping and then trying to get the boat planing again it starts to rev as if it's cavitating. When I pull back the throttle it's still in gear and will move forward albeit slowly.
I have tried a couple of different props,one new, so I don't think the hubs are bad. There are no grinding noises or any banging when I pull back the throttle.
It's the right gear oil (type C) and it's full and clean. I changed the oil after last summer and it was clean then as well. I have spoken to a couple of mechanics around here and none of them know much about the hydro electric drives or want to know. If anybody has any ideas before I take it apart it would be a great help.
Thanks
Tim

I would definitely check the props first. Use a permanent magic marker and draw a line across the inner and outer prop hub. Run in the water, then check and see if the marks still line up.

 

[Timok]

Re: 72 85 Johnson slipping gear

I'm in the water this morning I'll let you know
Tim

 

[tashasdaddy]

Re: 72 85 Johnson slipping gear

take a permanent marker, draw a straight line, to match cotter pin. like the picture. take the boat for a spin, make it do what it is doing. if the lines are still line up, it is not the prop, if misaligned, the hub in the prop has slipped, and need to have a new hub installed by a prop shop, or a new prop.

 

[chumchange]

Re: 72 85 Johnson slipping gear

I had a similiar situation with my 70hp johnson. She'd go fine, and all of the sudden,rev crazy high and go nowhere. Then would proceed as normal. Finally, she did this, and there was the dreaded clanking noise....going nowhere. I pulled up the motor to check the prop, which was fine. AFTER A LONG UP WIND PADDLE, WITH WATERSKIERS WAVING AT ME, I got the boat back on the trailer. Took it home, dropped the lower unit, pulled out the shaft carrier, and found the pinion gear was eaten alive. the front half of the teeth were just not there, probably a shimming issue. I hope your story is something simple, unlike mine!
Good luck! There is nothing on it that isn't replacable. Just convince the wife it's worth it!