50 hp force revves up but does not exceed 10mph

[gerkel]

I have a 1990 50 hp force outboard that starts great and runs great until I add 1 to 2 people. As I speed up the motor revs up but the boat will not go faster than 10mph. If I am by myself I can sometimes get it to get to normal speed if I slowly (I mean very slowly) push the throttle. When I get the throttle to halfway the motor revs up so high that I have to pull back to keep the motor from blowing. I have tried 3 different props and they all do the same.

What can I do to fix this?

As you can tell this is my first boat.

 

[Frank Acampora]

Re: 50 hp force revves up but does not exceed 10mph

We really need more information. What type of boat and how big, where are the peolple located in the boat, is the engine matched to the transom. A photo at speed would be nice too if possible.

It sounds like with the load, the prop is ventilating which may sound counterintuitive but you may be setting the prop in roiled or disturbed water from a protrusion on the bottom of the hull.

 

[gerkel]

Re: 50 hp force revves up but does not exceed 10mph

15' Maxum and it does not matter where the people are sitting. I have tried the motor at all three levels/positions. How can I test to see if the prop is ventilating?

 

[wifisher]

Re: 50 hp force revves up but does not exceed 10mph

mark the prop and the hub, to check if it is spun.

Use a center punch, knife blade or whatever you want, and mark both pieces. Drive a little and check your marks. If they have moved, you need to re-hub the prop.

 

[jerryjerry05]

Re: 50 hp force revves up but does not exceed 10mph

Check the prop and make sure the exhaust snout is still in place.Sounds like the hub is bad.If the snout is missing it will make the prop cavitate.J