Prop slipping

[crazy_s_dime]

Hey all, you may have seen my other post/build of my 64' crownline with 80hp west bend.

http://forums.iboats.com/showthread.php?p=2523838&posted=1#post2523838

I took her out today to take some friends out for labor day, and I was skipping around and after a while my engine would lose bite after a certain RPM. I couldnt get the boat to rise above 15 or so mph without the prop feeling like it was slipping. I tilted the engine up and put it in forward and tried to turn the prop by hand and even with the shear pin in and cone on, it still would turn just a little bit. Come to find out there is this brass insert that the shear pin goes through that looks like it is pressed into the back side of the aluminum prop, and it is spinning on that. I am supposed thats what is causing my slipping, and Im betting its not supposed to be doing that and it most likely no go any more. I need some help with this one, cause I cant find any prop info for replacement or anything. any help would be great.

 

[F_R]

Re: Prop slipping

If you are able to turn it by hand (without also turning the shaft), then it is slipping very badly. Think about it---that thing has to hold back 80 horses. I hardly think you are as strong as 80 horses.

The anatomy is that there is a rubber cushion bonded to the bronze hub. Then that whole assembly is pressed into the prop itself. If the bond betwen the rubber cushion and bronze hub fails, it slips.

With that said, make a mark on the cone and another mark on the prop itself, aligned with the first one. Then run the motor till the suspected slippage occurs. Now stop the motor and look at the marks. If they are no longer aligned, the hub slipped. If they are still aligned, repeat the test--there is a slim chance it stoped slipping in the same position.

I dont know what to tell you to do about it. A prop shop could replace the hub---IF they have a new hub. Not likely.

There might be a Chrylser prop that fits. I sort of assume that Force changed from a pin drive to spline drive, but assuming isn't very reliable either.

 

[crazy_s_dime]

Re: Prop slipping

yeah F R, that must be my problem. it IS slipping, there is no doubt about that. it always starts slipping at a certain rpm. well, now I need to figure out what to do to get a different prop on there, all it has is one 5/16" dowel hole in it for the shear pin. everything else on the boat is working just fine, so If I could get this problem solved, it would be grand!

 

[crazy_s_dime]

Re: Prop slipping

anyone know of a place I can buy a new prop or retro fit kit for this??!?

 

[crazy_s_dime]

Re: Prop slipping

did some research, its a michigan PJ51 Prop with 13" diameter and 8 degree pitch. I have found some used and or new old stock in box on ebay for 100-150 bucks. should I be able to trust a NOS prop to not leave me stranded again?

 

[F_R]

Re: Prop slipping

I'd trust a NOS one as much as any. Can't say as much for a used one.

Really?? only 8" pitch?? Well, if you say so, but that doesn't sound right to me. That sounds like a barge prop.

 

[crazy_s_dime]

Re: Prop slipping

all I know is that the prop model number comes up with a 13 x 8 description and the guy on ebay says it will match my current one on there. I found another guy with a NOS one for 80+ shipping, probably going to go that route.

check out my boat thread, i posted some in water pics