If I had a clutch it would be slipping

[Red Delicious]

I have a 1996 Maxum 2000 SRL with a Mercruiser 3.0 L/LX on a Alpha 1 Gen 2 outdrive. I have three props one is a High 5 I've had since I purchased the boat in 1995. A second one I've had for several years is a Turning Point Hustler 14.25X21

Aluminum,​

the last I just bought a few months ago, it is a Michigan Wheel Vortex XHS also a 14.25X21 Aluminum.

The High 5 is my ski/tubbing prop and works as it has all these years. Same speed at the same RPM and have the same hole shot.

With the Turning point I can cruse at 36 MPH @ 4,500 RPM when I put the new Michigan on I get to about 7 MPH and then the engine RPM jumps to 5,000 and the boat stays at 7 MPH. If I back the throttle off I can gently get it up to 20 MPH @ almost 5,000 RPM. I've double checked the hub and splines, put it in gear and tried to rotate it to make sure it's not slipping and there isn't. If I was in a car I'd think the clutch was slipping.

Any thoughts on what might be going on?

Thanks

 

[Red Delicious]

Both 14.25X21 are 3 blade props.

 

[flyingscott]

You won't be able to turn a slipping hub by hand. Mark the hub across the rubber and metal and take it for a ride. If the marks move which I guess they will. The hub is slipping.

 

[jimmbo]

You have the correct Hub Kit for the new prop?

 

[Red Delicious]

Thanks flyingscott, I'll give that a try when I can get back to the water.

jimmbo - It's the hub kit that came with the prop and says it's for an Alpha I'll take a closer look at it. Thanks for the help.

 

[QBhoy]

If it’s not the hub slipping it sounds like the typical reaction of a vented prop like the merc pvs (horrible things). Not overly sure that prop has vents though.