slipping at high rpms

[gary randall]

Hello,
My reversing gear is slipping when I am moving forward at higher rpms. It is more or less just a nuisance because the slippage begins at a speed that is just above the engine's comfort level.
Things are working well otherwise and I am tempted to just ignore it. The boat will cruise along just fine if I don't push it.

So, the question is, should I ignore it? Or, is it a sign that the reversing gear needs adjustment?

[Loki9]

I would adjust it. Letting it slip promotes wear and although you only notice the slippage at high RPM, it may be slipping at lower RPM too.

[Mo]

Are you sure you are slipping or cavating and hitting max speed. If the engine rpm's come up dramatically you may be slipping. If the rpm increase and seem consistent with the increase throttle, yet no increase speed, the prop may be cavatating.

[seapadrik]

I would like to hear more about the difference between slipping and cavitation as well, and what if any tests there are.

My gear was not adjusted properly and a while back it was slipping at something like 1500 RPM. I went in and adjusted the nut to what I think is the max setting and still be able to shift into forward detente.

Now , I can get to 1900 RPM at the dock and 2100 in open water. At the max RPM, when I increase it more it seems to shoot to close to 3000 RPM, then of course I back off. I wonder if I advance one more notch on that collar might be just right.

[Mo]

Sure sounds like it needs to come another notch...worth a try. Mine will increase rpm but not pick up speed, however, the rpm increase is not a "run-a-way" increase such as what we'd have with idle. The engine remains under load, however, there is no increase in speed. At this point, cut back the throttle to where you have max speed and lowest RPM.

Prop type, size, pitch,... and boat size all come into play of course.