Running Hot

[dale1]

Greetings, I just bought a 2000 Yamaha 150, 2 stoke. It runs hot after 2 minutes of idle. "alarm sounds" I took cover off. could not put my hand on the cylinder heads. not sure how hot it should be. I changed the water pump with a new kit. housing, plate, etc. "no help"

I removed the thermostat housings. did not find thermostats????

any help appreciated

 

[axolotl]

Re: Running Hot

Seems like last owner knew about the problem.
Check/replace the pressure control valve.
If outboard was used in seawater, salt scale might have been build within the block, or a blown head gasket might allow exhaust gases in the cooling system.
As soon as you pinpoint the cooling issue, replace the two thermostats.
Good luck and let us know what was the issue and how you rectified it

 

[dale1]

Re: Running Hot

Seems like last owner knew about the problem.
Check/replace the pressure control valve.
If outboard was used in seawater, salt scale might have been build within the block, or a blown head gasket might allow exhaust gases in the cooling system.
As soon as you pinpoint the cooling issue, replace the two thermostats.
Good luck and let us know what was the issue and how you rectified it

OK, thanks. it is a salt water boat. however, we took it to a fresh water lake today. Warning alarm did not sound. I was afraid to let it idle to long. longest period was about 2 or 3 minutes. how long should i be able to let this motor idle. water temps were mid 60s. where is the pressure control valve located? How can i descale the motor? thanks. dale

 

[jtwalker]

Re: Running Hot

I am having the same problem I had the water pump changer last year some one told me it was probably the thermostat where is the thermostsat does anyone have a diagram

 

[dale1]

Re: Running Hot

Jt. I changed the water pump because of a warning buzzer. It could have been a oil issue "2 stoke oil" I'm not sure. I'm on a steep learning curve, since i've only had the boat a week. anyway the pump did not stop the buzzer at idle with the water hose hooked up. on the lake it did not buzz.

the water thermostates are on top the cylinder heads. 4 bolts the thermostat housing. they are really easy to change. the best diagram is in the parts section of this site.

hope this helps,
dale