Yamaha 85 temperature

[Marlinman10]

Hey Guys, What temperature should a 1995 85hp Yamaha run at at cruise speed? After running at cruise, I could take the cover off and put my hand on the cylinder head and keep it there. Seems it should be running hotter than that. I have a little gadget that I can point at it and push a button and it shows the temperature. It read 100 degrees. Could this be right? Any ideas or suggestions would be appreciated. I'm thinking that the thermostat could be stuck open.

Thanks!

Mike

 

[robert graham]

Re: Yamaha 85 temperature

Thermostat closes in the 130F range and opens in the 180F range, but if your motor is running well and your spark plugs are clean and tan(not black/carbon from a rich mixture) then you're probably just fine. Are you having any problems? Good Luck!

 

[99yam40]

Re: Yamaha 85 temperature

pull the thermostat and test in a pot of water to see what temp it is opening, how far it opens and the temp it closes and compare to specs in manual.
Check and clean PRV to make sure it is not stuck open.
Look at passages and clean as necessary.
This is regular maintenance that needs to be done along with changing the water pump

 

[Marlinman10]

Re: Yamaha 85 temperature

Thermostat closes in the 130F range and opens in the 180F range, but if your motor is running well and your spark plugs are clean and tan(not black/carbon from a rich mixture) then you're probably just fine. Are you having any problems? Good Luck!

So i guess the awnswer to my question is it's running cold. If it opens around 130 then i shouldn't have a temp of 100? and yes my plugs are black and it's running rich. I need to change them every 3o hrs or so. My thinking was if it's running cold this could be part of my problem.

 

[robert graham]

Re: Yamaha 85 temperature

Probably time for a new thermostat so your motor can operate at a normal temperature. Plugs should be a fairly clean and tan color although a lot of trolling or "idle speed" can foul plugs some. I try to run my motor wide open some to maybe "blow out" the carbon and oil from the cylinders and combustion chambers. Good Luck!

 

[Marlinman10]

Re: Yamaha 85 temperature

pull the thermostat and test in a pot of water to see what temp it is opening, how far it opens and the temp it closes and compare to specs in manual.
Check and clean PRV to make sure it is not stuck open.
Look at passages and clean as necessary.
This is regular maintenance that needs to be done along with changing the water pump

What's a PRV?

 

[Marlinman10]

Re: Yamaha 85 temperature

I removed the thermostat and checked it and it worked fine. I went ahead and replaced it and took the boat out for a ride. The motor runs the same temp so I guess it's fine. I need find someone to clean the carbs since it runs rich at slow speeds. I've checked around here but no one wants to work or they want 750 to do the work.