01 Yamaha OX66 200 port side running hot

[Puttering]

Overheats shortly after running WOT. First time it happened, buzzer sounder and rev limiter engage. I pulled the cover off for a while to cool it off... then it was ok. I replaced the waterpump and the same thing happened again. I immediately checked the temperate of the heads with inferred thermometer. the port side was about 160? vers 120? on the starboard side. I did a bench test on port thermostat several times. It opened up a little slowly but fully from 140? up. It would not close fully until below 100?

 

[Puttering]

Re: 01 Yamaha OX66 200 port side running hot

Is there a Doctor in the house? No, serious.... Anyone every have this happen. I guess I could try to run it without the thermostat and see what happens.

 

[rodbolt]

Re: 01 Yamaha OX66 200 port side running hot

why not simply change the thermostats, they dont live forever.
DO NOT run it without the t-stats, they are part of the water pressure control system.

 

[Puttering]

Re: 01 Yamaha OX66 200 port side running hot

I went ahead and put in a new thermostat, I will have to wait till the weekend to try it.

 

[Puttering]

Re: 01 Yamaha OX66 200 port side running hot

Still overheats. I was running not more then a mile at mid speed when it happen. The port head was 200? while the other 120? I was able to run it at idle speed ok.
What could cause only the one side to overheat?

 

[jeffersondodson561]

Re: 01 Yamaha OX66 200 port side running hot

If your motor ingested some sand or dirt could possibly be problem, have you checked the pressure relief valve?

 

[Puttering]

Re: 01 Yamaha OX66 200 port side running hot

It's very possible I may have sucked up sand and shells before all this started happening. Whats the best way to go about checking the PRV? I will do a search as well. Thanks!

 

[jeffersondodson561]

Re: 01 Yamaha OX66 200 port side running hot

Check to see if the seat is not worn, it will be on the back of the motor, identified with a hose going to it.

 

[Puttering]

Re: 01 Yamaha OX66 200 port side running hot

Jefferson, thanks for the diagram.
I open the valve housing. The valve and seat were in good condition. The housing was very corroded.

 

[Puttering]

Re: 01 Yamaha OX66 200 port side running hot

I pulled the head off and there were blocked passages from chunks of corrosion. Funny how just the one side ran hot. Do I open the other side or wait and see? When I torque the head bolts, how can I get to the lower bolts behind the cowling with the torque wrench?

 

[Bob Gilvary]

Re: 01 Yamaha OX66 200 port side running hot

I pulled the head off and there were blocked passages from chunks of corrosion. Funny how just the one side ran hot. Do I open the other side or wait and see? When I torque the head bolts, how can I get to the lower bolts behind the cowling with the torque wrench?

I hope you changed the head gasket. As far as torquing the lower bolts, if you can't get a torque wrench on the bolt, just use a wrench. See how much pressure it takes to slightly move one of the torqued bolts and go on to the lower bolts with the wrench. Clean all the threads before reassembly.

 

[Puttering]

Re: 01 Yamaha OX66 200 port side running hot

Gaskets are on order. I will try the wrench. I noticed there is a plug on the top of each head. I wonder (a little late now) if there is a way to back flush through there without having to disasemble?