yamaha 150 overheating?

[bruingtonbeagles]

i have a 1987 yamaha 150 that seems to be overheating.the motor will rev up to wot when first started cold but after about 2or3 minutes it will only rev to 2000rpm if i pull the temp sensors out of the heads it will rev to wot.i noticed the water coming from the pee hole is cold?even when engine is to hot to touch.so i removed the t-stats and the water from the pee hole is still cold?is the waterpump not circulating cooling up into the motor properly?what could cause the overheating?thanks any info would be greatly appreciated,i need to go fishin....

[99yam40]

Replace the water pump, stats, and RPV.
If it still overheats open motor up and clean water passages

[bruingtonbeagles]

thanks , where is the rpv located? i took a cover off where the main water line comes into the motor next to the water indicator hose and there was a spring and a plastic insert in there is this the rpv?

[boats.net]

Pressure control valve is number 35 in this diagram, 1987 150ETXH Yamaha Outboard CRANKCASE CYLINDER Diagram and Parts

[bruingtonbeagles]

thanks for the info.is it possible that the garden hose and ear muffs just arent supplying enough water to the engine?all of the overheating issues i described were on the muffs not in the water!has always ran with no issues on the water.

[99yam40]

Yes the larger outboards can have a problem on hose, but might wait for someone with a motor like yours to chime in

[bruingtonbeagles]

update...i took the boat to the river today and backed it down in the water and fired it up,it ran perfect!let it run for about 20minutes with no issues the heads never got to hot to touch.it seems my water hose and ear muffs do not supply sufficient water flow...the pee stream was very good and even warmed up with the motor..thanks guys for all the help!me and the wife are going out in the morning for some monster cats!!!!!

[Bluefish]

It’s not a good idea to rev up motor in natural and out of gear

[happy1gilmour]

I had the same issue with my 08 F150 when flushing the motor on my muffs and hose. I found that if I had the hose on anything but full flow and finding muffs that supply water to both sides of the water intakes and not just one side like the standard muffs I dont have a issue any more.

Water pressure at your place could be lower as well which wont help.

regards