[rockmike]

I have an 80Hp(115 powerhead) Yamaha Jet that overheats at idle. I've had it back to the dealer four times, and they have checked all the obvious things(thermostat, obstruction, water pump), but it still overheats if you run it below 1000rpm for any lenght of time. There is no problem at higher RPM's. Any ideas? It's 100 mile roundtrip to my dealer, and I'm losing patience.

[rodbolt]

with no other information I would check the pressure control valve and grommet for debris/distortion. a water pressure test would be nice.
then check the actual temp with a temp gun.
also check the actual jet impeller for proper impeller clearence as this is where the seawater pump for engine cooling gets its water from.
as the engine is under the least stress at idle look for something that would create a low water pressure in the block condition.
also double chect the part number of the pump kit that was used as most jets require different housings than a standard outboard.
its haooened before anyway.

[rockmike]

Originally Posted by rodbolt

with no other information I would check the pressure control valve and grommet for debris/distortion. a water pressure test would be nice.
then check the actual temp with a temp gun.
also check the actual jet impeller for proper impeller clearence as this is where the seawater pump for engine cooling gets its water from.
as the engine is under the least stress at idle look for something that would create a low water pressure in the block condition.
also double chect the part number of the pump kit that was used as most jets require different housings than a standard outboard.
its haooened before anyway.

Most of this has been checked. I suspect it has the wrong water pump, because the literature on the motor cautions that it requires a new design water pump. Would have thought it would have come with the right pump, though. Guess it's like going to the Dr.----sometimes you have to diagnose yourself.