Drive Slipping

[DLindow]

This is my first boat. I put it in the water for the first time yesterday. At about 10mph the drive would start to slip. If I tried to go faster it would just rev like it came out of gear.

The guy I bought it from said he rebuilt the lower and replaced the upper. the serial plate does not have a number on it. I did find this number on the side. 94992s.

[Tech Support]

It is most likely the prop hub or coupler. Read this thread for more info. http://www.sterndrive.cc/vbforum/sho...hlight=coupler

Tech Support

[Bt Doctur]

drive

what kind of motor , what kind of drive? what service was done?
drive oil level checked?,engine alignment checked?
Slipping could be the prop hub, Remove prop, mark a line on the hub and retest, lines don`t line up,prop hub slipping.
Can also be the engine coupler. With the ign key in your pocket, shift into fwd gear, have someone watch the shaft inside the boat where it enters the engine, and stand on a prop blade and try to turn it. Shaft at engine turns,then coupler is slipping, prop turns and shaft dosent, drive issue.

[DLindow]

He said the motor was rebuilt 2 years ago and the whole outdrive last year.
He rebuilt the lower and bought a used upper.

Mercruiser 3.0 Alpha one

[DLindow]

If it is the prop hub I think I will go ahead and get a new prop also.Its in pretty bad shape.

What is the correct size prop? The boat is a 1984 Harbor Craft 17.5" I can't find any numbers on the prop.

[starcraft21foot]

I think you have a good chance it is a prop hub, I have heard of similar problems with the prob hubs. Engine couple I doubt, I had a engine couple failure and it was all of a sudden, when from trolling to no forward in a matter of seconds.
Also may want to try an adjustable prop (westmarine), composit 4 blade prop and allows you to adjust the pitch. I have had one for 4 season and like the prop, I am able to fine tune the pitch. They also have replaceable blades if you hit a rock. I have a 21 foot starcraft cuddy cabin with a 3.0 chevy 4 cylinder with a se 106 outdrive.

[DLindow]

I marked the prop and took it out today. It ran fine no slipping. I don't under stand. The load was about 300lbs lighter.

[starcraft21foot]

I have only had one boat 86 starcraft, but I had to do a lot of work because owner prior to me put an old merc 140hp outdrive in it. So during the past 4yrs of working the bugs out I have had the outdrive off, split apart, new engine coupler, new boots, other gimble housing parts, replaced engine in 2007 (broke timing gear), new se 106 in 2009 (old merc. 140 had rust on the gears) and other work. Never the same thing twice. By all means I do not know everything but have a good idea of how the outdrive works.
The power is fed from the flywheel on the engine, through engine coupler, driveline to outdrive, then to the prop. My assumption is if the metal to metal drive splines in the (engine coupler, outdrive) slipped they are gone. So I still think it could be the prop (rubber hub slip), or ???. Any metal or discolloration with your outdrive oil. Not sure if it could be the outdrive fwrd/neutral/rev clutch) I have never tore the lower unit of an outdrive apart so not real sure if something in the lower unit could slip intermittently. If you fish on a lake you can probably get to shore and change the prop (keep a spare). If you fish ocean you are out of luck until you get back to dock. This assumes the prop is the problem.