Force 50HP prop stops spinning at full throttle

I have a '85 Force 50hp on a 14' Bayliner Capri. Have had it out many times since buying from a friend 10 years ago, and it has been very reliable.

Well, I had it out in the bay last week, and after fishing all day, we put up and started heading back in. For the first time all day, I gave it full throttle, and it was very sluggish getting on a plane. I honestly thought something was wrong, but it is the most weight I have ever had in that little boat (3 grown men with ice chest, etc, and we had taken on some water from wave action), and so I thought that was the reason for the sluggishness.

Well, it finally got to full plane, and was at normal mph. Then, after about 10 seconds, I heard a loud noise and immediately lost power (motor kept running, but boat fell out of plane). I thought maybe I had hit an oyster reef or sand bar, but did not notice any mud in the water behind me. I brought the throttle back to neutral, then tried to go forward again, but the motor just revved (very smoothly I might add), but no forward motion. I tried several more times, and same result. I then very slowly put it in forward gear, and noticed that the boat had a slow forward motion. I limped back in to the ramp like that.

Back at home in my driveway, the motor runs fine, and the prop spins fine in gear.


So, I would really like suggestions for my next steps.

I am planning to mark my prop to see if the hub is slipping next time I take out. But what else can I do to make sure I won't have a problem on the water?

Any help would be GREATLY appreciated. Sorry for the length of this post.

Re: Force 50HP prop stops spinning at full throttle

Sounds like a spun prop.
And a badly spun one at that.

Engine OFF, put it in Forward and try to turn the prop with all you can muster by hand, Backwards, Counter Clockwise.
If you CAN turn it, the prop hub is spun.
If NOT, that doesn't mean it isn't.

But at least you save the time of taking it out again!

Re: Force 50HP prop stops spinning at full throttle

Uncle Willie is right, you have a spun hub. mark the hub and prop, and if the marks don't align after running it a WOT for a bit, its spun.

Re: Force 50HP prop stops spinning at full throttle

Since that motor uses a pin drive, it's possible that the "pin" has sheared.

Re: Force 50HP prop stops spinning at full throttle

All,
Thanks much for replies. I will definitely mark the prop before taking it out to check for slippage. By the way, I took my prop off and verified my shear pin has not sheared.

A friend told me to check my shift linkage as well, to see if it has slipped a little. Does that make any sense based on my symptoms?

Re: Force 50HP prop stops spinning at full throttle

It is NOT a shear pin, it is a thrust pin. The shaft splines drive the prop. The pin takes all the forward thrust. If the pin breaks, the prop will slip backward and contact the gearcase housing.

NOW: Your prop is spun, no doubt about it. You can send it out for re-hubbing or buy a used on on the auctions for about the same price. You can also "Pin" the prop, in essence making it a solid hub that will never slip again. These are bronze props that I have pinned. You can clearly see how I have drilled and tapped the hub to accept three stainless 1/4 X 20 (long) set screws.

Re: Force 50HP prop stops spinning at full throttle

Yes, I definitely have a spun prop. I put it in gear as suggested, and was able to get the prop to slowly turn by hand.

Thanks all very much. Saved me a trip out in the water only to have it spin again.

I am now a huge fan of iboats.com !!!!