yamaha C40 running hot

[jl_photo]

My 1996 C40 seems to be running hot. The warning buzzer keeps going off.


I have lots of water at the pisser. new water pump last season.

If I remove the thermostat housing, lots of water comes out at idle.

I tested and installed a new thermostat.

I tested the heat sensor in boiling water. it does not come on at 212 degrees.

I recently removed the head. It was clean inside and so was the water jacket.

I did not remove the side cover.

when the buzzer goes off the block is warm, but not so hot that I can't leave my hand on it.


The engine is on a tunnel hull. Could i be getting a little air trapped in the top of the cooling system?

 

[jl_photo]

Re: yamaha C40 running hot

???? I removed the thermostat and the buzzer is not going off now.

 

[Yamajoe]

Re: yamaha C40 running hot

Im not sure if this model has a grommet located in front of the thermostat, if it does, pull the grommet out and clean, flush the motor while you have the Tstat off; i wouldn't run the motor too long without a Tstat.

 

[rodbolt]

Re: yamaha C40 running hot

at 212 the temp switch should be closed.
double check your test procedure.
as far as water pressure simply install a pressure guage. especially since your running a unique hull.

 

[pine island fred]

Re: yamaha C40 running hot

You mentioned that you did not remove the side cover. Under no circumstances should you consider putting a wrench to those 12 or 14 bolts!
Trust me, you have adequate water flow around the exhaust. Look somewhere else. FRED