Spun Prop Hub?

[2004_3300_SCR]

Apologies for the non-Maxum content, but in addition to the 3300 I have a 20' 1998 Crownline bowrider lake boat that I bought in the summer of '19. Power package is a 350Mag / Alpha 1.

Question is - how common is it to spin the hub inside of the prop? It has a 3 blade stainless prop on it, don't recall the size and brand offhand but I pretty sure it is a Mercruiser branded prop. The holeshot was great when I first bought it - it would pop on plane in seconds with almost no bow rise. Now it seems to rev higher without accelerating as hard. Feels almost like a slipping auto trans that catches eventually - when it catches you can feel the boat accelerate a little bit while RPM simultaneously drops a few hundred RPM. Feels to me like the hub may be slipping inside the prop and eventually it re-locks together when there is enough friction. Is that common, or is there some other phenomenon that could be going on? As far as I'm aware when it's in forward gear, from the prop to the engine is a direct gear drive, so either the prop is hydrodynamically slipping in the water (I checked and all the lobes are there and in good shape), or the hub is spun.

[Phillbo]

It happens.. Have the prop checked by a prop shop and also take a look at the coupler.

[mmwjr]

I had it happen twice, once from hitting bottom and the other the old rubber just failed.

[gamoooos]

it's so cheap to change it yourself, just do it. I don't do any mechanical work on my boat, and this was the easiest thing you can do yourself. Props are available everywhere, even on Amazon, and it takes 15 minutes to do the job yourself.

[jparsons121]

Easy to verify. Mark the hub and the prop. Go for a short ride with a few brisk ‘high acceleration’ starts. If the marks aren’t still aligned, the hub is slipping.

I use a small center punch on the larger boat to mark the prop nut and the prop. Tried Sharpie on the small boat and it kinda worked. (That’s an outboard, so the prop is a bit less slimy).

[shrew]

Is that a repower? The 300HP engine is right at the bleeding edge of the specs for an Alpha I outdrive. Max RPM for the Alpha I is 300 HP, which should be the HP for a 350 Mag MPI Engine.

All you would need to do is overload the boat, or horse the throttle on an aging hub. Going from zero to wide open throttle attempting to pull a slalom skier out of the water might do it.

[2004_3300_SCR]

Thanks for the replies. Glad to hear this is relatively common. Been boating forever and wrecked an aluminum prop or two but never had one spin it’s hub.

Not repowered to my knowledge - the prior owner had been slipped a few over from me for almost 20 years. The boat never really went anywhere - it was an older gentleman; occasionally his adult son would bring his kids and take it out for a bit. When he decided to sell it I jumped at it ... came fully stocked with vests and toys since he was getting out of boating. From the rub rail up it looks practically new - it was always under a mooring cover.