1990 200hp over heat..

[Sponge_bob]

I just got the boat back form the an authorize Yamaha repair shop and they have given up after charging me 400 bucks for a whole bunch of parts that I didn’t need.

Engine runs great at low RPM and the starboard side of the engine runs 30 degrees hotter above 3200 rpm.

They replaced both thermostats, the pressure relief valve, all the gasket that are on the top of the engine block and got me a whole bunch of new bolts, compression check, leak down check but the problem still remains. They claimed to have spent over 10 hours on the motor trying to isolate the problem but since they were not able to solve it they were not willing to invest any more time in it. They claim the last option is to remove the power head and check the base plate and they couldn’t guaranty that would solve the problem.

i went to the dealer because I figured that they would be able to diagnose any problem. What am I to do?

[dtmackey]

Sounds like you have a blockage of some sort preventing the full flow of water to cool the engine. If this is the case, your options are very limited and removal of the powerhead is likely.

I would be looking for $400 back if the problem was not fixed.

David M

[Hamfisted]

Did they pull the heads and clean out any mineral buildups that could be blocking the cooling passages? Did they install a new waterpump? How are you reading the temperatures on the heads? With a IR thermometer? If you don't have one already go to www.Yamahapubs.com and order a service manual for your motor. In all that stuff you never said if they replaced the waterpump or not.


Mike........ Miami, FL

[Sponge_bob]

the water pump impeller was replaced in october of last year. They took it apart and verrified that it was in exccellent shape. I am sure they would charge me for one if it had just a bit of salt on it. I only have 10hrs on it since the lower unit was resealed and the water pump replace.

They did not want to pull the power head because they couldnt guaranty that would solve the problem. most of the local shops are refusing to even look at it now. the manual arrived a couple of days ago but it doesnt have a clear cooling chapter in it. I expected to see a water cooling diagram but...

[Sponge_bob]

someone told me to check the temperature of the water that comes out of the side stream to see if it's warm. Is that an indication of anything or is it fishing?

[Ken]

SpongeBob,
Yea, the Yamaha service manual is accurate for what it has in there, but, boy, they sure leave out a lot as far as theory of operation, etc. is concerned.
I am curious as to how you are reading 30 degrees hotter on starboard side of your motor vs port? Do you have temp sensors and gauges for both sides? Is the temp the same up to 3200 rpm?
From what has been done to your motor so far, I would suspect waterjacket restriction of some kind - eiher in the cylinder assy/and/or the heads. You might try a cooling system flush with "Salt-Away" or "Salt-Terminato". Probably won't make any differenc, but is worth a try to remove possible salt/mineral builup. Other than that, the heads will have to be removed and inspected for buildup and cleaned out.
The side stream discharge won't give you an indication of cooling - only water pressure from the pump. I think it completely bypasses the water jackets - just gives you an indication that the water pump is working.
Good luck,
Ken K

[kotzebuealaska]

With the lack of parts available around here (and cost with shipping) we run engines (mine a 1992 200) without thermostats. Old timers started taking them out when the buzzer went off and have been running them since. NOT recommending to others but just letting you know what we've found. Takes a little longer to warm the engine up but that's OK. Even running in spring and fall through ice-water (floating ice) is OK.

[Ken]

alaska,
That's hilarious! Here we are down in these relatively warm waters, and we get worried about thermostats and a few degrees diff in temp of port vs. starboard, and you guys just say the heck with the thermos and throw them away. I'm still chuckling.
I guess that just shows you how tough these Yamahas are. And, yes, I will still run thermostats in my C115 - because I'm so darn anal about keeping everything perfect with my boat, motor and trailer!
Good luck,
Ken K

[Pete1]

Sponge_bob,

Did you ever find the reason for overheating?

I have same "problem" the starboard side is warmer than port side ,just feel by hand.

I haven`n notest any problem ,yet....

Pete