Water pump appears not to work after 2900 rpm

[Jessie Hill]

I have just installed a used very low hour 1992 90 HP Force. It has great compression on all three cylinders; starts and runs good up to 2900 RPM. After 2900 RPM the water pump seems to quit working. There is no exhaust stream or mist. If I keep running it over 2900 RPM, the overheat alarm goes off after a few minutes. Any idea what the problem could be?

 

[roscoe]

Re: Water pump appears not to work after 2900 rpm

Hi Jesse, welcome to iboats.

Time to replace the water pump impeller.
They wear out, and need replacing every few years.

 

[Jessie Hill]

Re: Water pump appears not to work after 2900 rpm

I had the impeller changed out, by my regular mechanic, before I put the motor on my boat. Would a bad water pump work up to 2900 rpm and not after? I tried to put the motor in neutral and rev it past 3000 RPM to see if the pump worked after 3000 RPM, but the controls seem to have a governor on it to not let one rev past 3000 RPM in neutral. It worked fine in neutral up to 3000 RPM. I was wondering if the design of the foot was causing the water to cavitate around the intake holes.

 

[roscoe]

Re: Water pump appears not to work after 2900 rpm

I was wondering if the design of the foot was causing the water to cavitate around the intake holes.

Not the design of the foot..... But if the motor is mounted too high, or trimmed out too far, the water intakes may be out of the water.

 

[Jessie Hill]

Re: Water pump appears not to work after 2900 rpm

Not the problem; made sure motor was completely in the water and the intake ports were in the water about 18".