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Author Topic:   Yamaha 200 overheating
greyg8r posted 03-24-2004 07:50 PM ET (US)   Profile for greyg8r  
One of my 1997 Yamaha 200s (the Saltwater Series, if that makes a difference) has an overheating problem. The engine has only 100 and change hours since 1997. The previous (original) owner had not replaced the water pump or thermostats. My mechanic replaced the water pump and thermostats and it still overheated. He then took off the heads and inspected for clogging of the water ports, but said they were surprisingly clean. He then reassembled it, but without the thermostats, and it did not overheat.

The marine mechanic says to run it with the thermostats requires removal of the blocks to fix the problem. He estimates this will cost $500 (8 hours @ $65/hour), if no problems develop.

So, it runs fine without the thermostats and, in Florida, that is not a problem. I am content to run it as is until or if the problem worsens and then fixing it for good. But... not knowing what the true problem is is driving me crazy!

Any ideas?


TampaTom posted 03-24-2004 08:50 PM ET (US)     Profile for TampaTom  Send Email to TampaTom     
Does it overheat at idle, high speed or both? After your mech put it back together without the thermos, did he try it one more time with the thermos? Did he check the water pressure before and after? There might be a water dump (poppet valve) that is not opening at higher speed and allowing heated water to leave the engine faster (which I assume removing the themos is doing.) Are all the water carrying hoses clear? Did he backflush it? You might find something on the Screem and Fly forum. Not many racers running Yamahas, but those guys know a lot about engine cooling.
greyg8r posted 03-24-2004 10:54 PM ET (US)     Profile for greyg8r    

The engine will overheat quite quickly at speed, within 5 minutes. It will overheat at idle, eventually, but takes longer.

He has not tried running it with the thermos after removing the thermos.

I will ask him if he checked the water pressure and also about that poppet valve, which I had not heard of.

I will check out the screem and fly webpage.

By the way, where do you live? What kind of boat do you have? Where do you usually boat?


John from Madison CT posted 03-25-2004 05:13 AM ET (US)     Profile for John from Madison CT  Send Email to John from Madison CT     
Go here and ask for Rodbolt:;f=30

He is truely a Yamaha expert AND will give you great advice with prompt replies.


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