Slippage?

[Shallow Minded]

Posting a question on behalf of my brother.... he's running a 20' Crownline open bow, stock 454 Mercruiser with Bravo 1 outdrive. The boat has about 250 hours on it and has always ran really well.
Long story short, the boat seems to have a "slippage" problem that just randomly occurs. We'll run it all day and have no problems, then it'll show up. Engine sounds/feels fine, guages all check out, but it feels like the prop is simply not turning to match the RPM's. We've checked the rubber insert inside the prop and it appears fine.
Any ideas what might be causing something like this? Thanks in advance.
SM

[HP350SC]

Coupler?

[Shallow Minded]

That's what I was wondering. He had it replaced in August 2002 or something like that. I guess I thought a coupler either worked or did not work, with no in-between. We've heard from our local Crownline dealer that coupler failer is not uncommon with their BBC's.

[Shallow Minded]

So I take it the coupler seems to be the consensus?

[wideopen545]

check the hub in the prop again sounds like it might be slipping

[celeb1]

Prop might be cavitating or ventilating, pay attention to when the slippage occurs and make note of trim levels, trim tabs, turning radius. Could be something stupid like a damaged prop or even weeds on the prop.

[MANIC MECHANIC]

It's the cone clutch in the drive slipping...?
Ask in the outdrive section, it's a little slower in responses but I think you'll be told that that's the most likely culprit.
Good luck.
Tim