1976 OMC Outdrive slips when underway..

[jmr11]

Hello folks, any help with this would be much appreciated. Older 246 Aquasport with 351 Ford and OMC outdrive with electronic shift. Problem developed recently. When underway just about when the boat would go on plane (and be under its heaviest load) I would get a slipping or spinning sound from the outdrive and would lose forward motion. As soon as I came back on the throttle everything would reengage and run fine and if I slowly accellerated I could get back on plane. Now however, not only does this slippage (for want of a better description) happen as boat planes it will sometime happen when boat is cruising. I have tried changing props as initially I thought it might be cavitation but it still happens so I have ruled that out. Hoping against hope but could this be a clutch problem with the pesty spring assembly in the lower unit. Thanking in advance for any direction with this thing.

 

[Kovah55]

Re: 1976 OMC Outdrive slips when underway..

Ball gears good ? Prop has a pin so the prop isn't spun. Really sounds to me it's the coupler, don't run it anymore till you pull the motor and have a look see at the splines on the shaft and the splines on the coupler.
You can pull the motor, without pulling the drive on stringers. Just have someone support the drive when you pull the motor. When you have everything loose from the motor, just lift the motor free of the mounts and slide forward 6 inch's and the shaft will come loose, then straight up with the motor.
If you find the coupler good, and you need a shaft i have 2 you can have for free just pay the shipping. But i think you will find the coupler is bad also, it's a one piece coupler no rubber on it at all.

 

[Kovah55]

Re: 1976 OMC Outdrive slips when underway..

I have given more thought to your problem sir. Do you know there are 2 shafts in the upper drive? One is the water pump shaft, that has splines, that enter the bearing carrier shaft,that also has a gear. Could it be that the shafts are about to go, and the splines are almost gone.
Only way to know is to drop the lower housing and remove the four bolts that hold the water pump. it will all come out in one piece,then you can examine the shaft splines.

 

[bruceb58]

Re: 1976 OMC Outdrive slips when underway..

Couple things...you could have bad shift springs. You may have a resistive connection to the forward shift wire. Is your ground wire between the drive and the intermediate housing there?

When you changed your gear oil did you use type "C" oil?

 

[Howard Sterndrive]

Re: 1976 OMC Outdrive slips when underway..

really sounds like a failing w/p shaft.
How many years since the splines were greased in there (i.e. when was impeller last changed)?

Prop has a pin so the prop isn't spun.

many pin type props still have a rubber hub that can slip

Also look for electrical issue and check the lower unit oil for water intrusion.

 

[jmr11]

Re: 1976 OMC Outdrive slips when underway..

Gentleman, thank you all for your suggestions. I will take your advice and see what I can do this weekend. Kovah, thanks for your generous offer, much appreciated. Bruceb, I suspected the clutch springs but how would one know if they were defective unless they were actually broken. Will double check ground. Have used OMC Premium Blend for electronic shift religiously. Howard, I am quite certain that the w/p shafts have not been greased in some time. As you and Kovah are suspecting something going on there I will definately check that out. Thanks again guys.