Yamaha prop disengages at high RPM

Coming in yesterday, my 200 HP Yamaha (1990)<br />prop seem to stop spinning. Engine remained at high RPM but no forward motion. I thought I hit bottom (was in deep water) at first. I started the motor and began going forward at slow speed and was able to make it back to the dock. When I tried to go at a faster speed, the prop seem to not spin or slip on the spindle. However the RPMs went up when I increased the gas. It acted almost like a burned clutch!!!<br />Before I pull the boat and take it to a dealer for repair, do you have any sugestions as to what it may be? I listen for noise in the lower housing, but it seemed to be running normal. I checked for any damage on the lower housing and there was none.

Re: Yamaha prop disengages at high RPM

The hub has spun in the prop. Remove it,take it to the prop shop and have it rehubbed.<br />If you didn't run aground or hit an underwater obstruction, you night wanna re-hub it,get another prop,and put the rebuilt one in the bilge,because it might be pre-disposed to spinning hubs... My Forces are.<br /><br /><br />------------------<br />the Early bird get's the worm...So, he don't have to stop for bait.

Re: Yamaha prop disengages at high RPM

What do you mean by "spun in the prop"? I had this same problem last week, but it stopped after I killed the engine and inspected. I hit a submerged tree limb at idle speed and the motor acted like the "transmission was slipping". Should I have it checked out? It is a '96 Force 75hp.

Re: Yamaha prop disengages at high RPM

"Spun in the prop" means that torque from the engine causes the rubber spline between the prop shaft and the prop to slip inside the prop hub. Thus rpms climb high, but the prop doesn't turn faster. Best analogy is to compare it to a car tire. When you floor it and the tire breaks loose, the tire spins, the speedometer climbs, but the car doesn't move. When you back off, it catches and it works fine again.<br /><br />Hope this helps.

Re: Yamaha prop disengages at high RPM

Whacking the prop on submerged objects will cause hub to "spin out", saves the gearcase. However, the rubber also can "dry rot" and will also cause the prop to "spin out". Re hubbing (sp?) is a cheap/easy fix.<br />Machine shops that do this can also "true" or rebalance the prop (in case you did whack something and put in bends or nicks).

Re: Yamaha prop disengages at high RPM

I had a similar problem yesterday - '96 70 HP Yamaha, crusing at 4500 RPM, engine started racing. Idled back to neutral. Slowly increased power and prop re-engaged, but now engine starts to race and prop disengages above 2500 RPM. The prop seems tight, and lower end seems OK when I try to turn it by hand. Could this be the same issue? Should I try a new prop?

Re: Yamaha prop disengages at high RPM

bjoreriw said:

I had a similar problem yesterday - '96 70 HP Yamaha, crusing at 4500 RPM, engine started racing. Idled back to neutral. Slowly increased power and prop re-engaged, but now engine starts to race and prop disengages above 2500 RPM. The prop seems tight, and lower end seems OK when I try to turn it by hand. Could this be the same issue? Should I try a new prop?

Click to expand...

Same issue, buy a new prop !!