2004 70c yamaha overheating

[gettbnt]

I have a 2004 2stroke 70 yamaha I ran thruogh mud, oops! ever since it wont go more than 2 miles wide open without overheating, thermostat opens around 130F, at idle water comes out of thermostat hole about 6 inches, water comes out of pee hole strong, temperature sensor closes at about 185F, impeller is a little scuffed up but not to bad, also buzzer and warning light comes on (please help! thanks)

[dtmackey]

Try a new impeller kit, could be scuffed enough to prevent full flow at the higher RPMs.

D-

[gettbnt]

Thanks dtmackey I'll try that

[Ken]

gettbnt,
Before you replace the impeller, check the pressure relief valve - it may be partially stuck open from debris. It is fairly simple to check. If it is partially stuck open, it can dump cooling water from the pump - this can be seen coming out the exhaust holes that are at the top of the upper casing. Is this what you mean by "thermostat hole"?
Good luck,
Ken K

[gettbnt]

Ken What I ment by thermostat hole is taking out the thermostat and looking at the water flow, but what you are saying is if water is coming out of the two holes under the cowling then its not the impeller, but if its not coming out then it probably is the impellar? (sorry I"m new at this)

[Ken]

gettbnt,
If you hook up the ear muffs (motor flusher) on the drive way and crank up the outboard, then most of the cooling water should be coming out with the exhaust in the center of the prop.
There should be a little exhaust and just a few drops of water coming out of the two vent holes at the top of the upper casing. If there is a lot of water coming out these holes, then that is usually an indication of a partially stuck open PRV. Since it is fairly easy to check, I would do that before I replaced the impeller. A Yamaha shop manual would be handy. On my 2000 C115 the PRV is located under the small round dome at the bottom of the exhaust cover - it has a rubber hose that is attached. On mine, the CDI unit has to be removed to get to it. Two bolts hold the PRV cover. The PRV itself is just a spring loaded valve that opens when pressure in the cooling system gets too high. If there is debris in the water at the time, then some can get trapped under the valve seat and cause it to stick open. Just check it to clear any debris and remove any deposit buildup on the valve and spring.
Good luck,
Ken K

[gettbnt]

Sorry one more question when I run the water muffs in the driveway is it normal to have water coming out above the lower unit where the rubber hose comes through the lower casing at the rear of the motor? (thanks) I think the hose is for gear case preasure relief.

[Ken]

gettbnt,
With the ear muffs hooked up and motor running, there will be water coming out the center of the prop with the exhaust and also out of the slotted holes at the top of the lower unit just above the ventilation plate and towards the rear. Also, on my C115 there are several other small round holes in the lower unit that water comes out of - this is normal.
Ken K