Drive still slipping after coupler replacement

[BillNH]

Hi all,

I've learned a lot from this forum and looking for some assistance. I've got a 1989 Sylvan V-188 with a 4.3L/Alpha One (Engine SN# 0C614566) that I've been working on. The boat was working fine until I hit a rock shredding the prop and cracking the lower unit. I replaced the lower unit, prop and hub, took the boat out for a test drive but couldn't get the boat over 2500 RPM without it "slipping." I marked the prop hub and shaft with a marker, took it back out and didn't see any movement. Pulled the engine and installed a new coupler and aligned the engine. Tried another test drive and still had the same slipping problem. I replaced the yoke shaft and still have the slipping. The marks I put on the prop are still lined up so I don't think it's spun.

Could the old yoke have stripped the splines in the new coupler? If I install another coupler, should I replace the yoke again as well? Is there something else I should check?

Thanks,
Bill

 

[achris]

Hello Bill and :welcome:

What do you mean by 'slipping'?

If the splines in the coupler were damaged/stripped out, then it's unlikely you'd get much above idle before the engine would feel like it wasn't in gear, lots of revs, no forward motion. In fact, any spline, once stripped out, will not transfer torque, they just spin.

If you're still moving at speed, but the engine revs, then it's more like you have air in the prop.

Chris.......

 

[BillNH]

Hi Chris,
I can idle out at headway speed but once I give it any throttle it feels like it's going to start moving but the engine just revs up and the boat doesn't move. It idles around just fine. I just double checked the replacement prop and realized it's the wrong part. The old one was a Quicksilver Nemesis 14x17p and the new one is 13.8x11p. Could that be the problem?

Bill

 

[achris]

Going from 17" of pitch to 11" is going to feel like you're still in first gear... Yes, that sounds like the problem.

 

[BillNH]

Thanks Chris, I never would have double checked that I received the correct prop. At least the coupler replacement allowed me to find a couple broken flywheel bolts and replace the leaky y-pipe o-ring. New prop is ordered and fingers crossed.

BTW, your videos were extremely helpful.

 

[BillNH]

The new prop is installed and I'm back in business. Learned the prop you order is not necessarily the one you receive. Thanks again for the help.

 

[Rick Stephens]

Nice!