1997 yam 40, overheat, steaming

[jackd1023]

Hello, working on this Yam 40 hp for my neighbor. I installed a new impeller and new thermostat because of overheating. It is still overheating. it pees, then steams, pees then steams...etc, while underway. On fake a lake..(MUFFS) it is fine.

I am going to backflush the system, it is freshwater only motor. any ideas??

 

[99yam40]

Re: 1997 yam 40, overheat, steaming

Check compression after overheating a motor.
Could be blown head gasket, plugged passages, impeller installed wrong, sucking air because of warped housing, etc.

My 1999 40 has a very hard indicator stream at idle on the water or on muffs, does this one?

 

[jackd1023]

Re: 1997 yam 40, overheat, steaming

Compression is 130

Stream is very good on muffs, they said that the water was streaming good but going from warm to cold and back to warm.

 

[jakelogsdon]

Re: 1997 yam 40, overheat, steaming

Seems like it might be something to do with the thermostat still. Take the thermostat off, see if it does the same thing????

 

[jackd1023]

Re: 1997 yam 40, overheat, steaming

Thats what I was thinking to do, I am going to pull it in the morning.

Does anyone have a idea on the best way to flush or is there any product I can use??

 

[99yam40]

Re: 1997 yam 40, overheat, steaming

They sell something called salt away, but I have never used it myself.
It is best to pull and test thermostat if you think it has a problem. Leaving it out will not allow the water to flow properly through the motor

 

[jackd1023]

Re: 1997 yam 40, overheat, steaming

Ok, does anyone know what temparature these are thermostats are supposed to open. I will test the thermostat in water if I knew when it is supposed to open.

Is there a way to "close the system" to do a leak test or a pressure test to diagnose?

 

[99yam40]

Re: 1997 yam 40, overheat, steaming

Should start opening around 120 deg F and fully open at 140 at least that is what my 1999 C40 manual says. It would be a good idea to pick up a manual for that one to get all the specs and info on repairs

 

[jackd1023]

Re: 1997 yam 40, overheat, steaming

Ok, I pulled the head off after determining that the thermostat was good.

I found that the bottom cylinders water jacket was completely clogged with deposits. It took me over two hours to scrape and blow all the crap out of there. I ordered the new gaskets.

I inspected the cylinders and as much of the pistons as I could see and they all look good, no gouges or cracks, the head looks good and now I can get air to move throughout the whole system.

Gaskets are on their way I will post results.

 

[ertlj]

Re: 1997 yam 40, overheat, steaming

even though air will pass u may want to pull the exhust manifolds and clean them