getting hot

[memaw777]

1984 mark twain 25 ft 350 260 hp runs fine at 3000 rpm. pulling kids on tube with hard acceleration it gets hot. has a new impellor and prop. whats most likely to make temp go up pulling tube.

 

[Sandy]

Possibly over pitched prop and excess load of tow strain and POB's , so the engine is no longer propped to reach mfgr's specified WOT range. Or the RW pump housing is scored to reduce suction at lower rpm when the impeller is still contacting the wear surface.

Is it RWC or FWC and do the tops of the riser/elbows get hot to the palm of your hand when pulling? That would be a good indication of insufficient cooling RW flow.

 

[cwms]

So what prop did you have and what do you have now? What was your WOT with the old prop and what is it now?

 

[memaw777]

wot is 4400 i think rwc does not have radiator it only gets hot when pulling tube at high rpm

 

[HappyKamper]

Sounds like the water pump is scored. Remove the impeller and feel the end cap and bottom of the impeller pocket.
If there are ridges, then you need a new pump. The impeller is not pulling water thru at high RPM's.

 

[cwms]

When was the last time manifolds and risers were replaced? If it's been a while, they may be clogging up. Not enough to cause overheating during normal operation, but enough to overheat when putting a heavy load on the engine.