70hp Over Heating

[CaribouHills]

I have an over heating problem on an 2003 Yamaha 70hp, 2 stroke, but only in gear at idle speed. The motor has approximately 700 hours and is ran in fresh water only. <br /><br />Do pre-04 70hp motors have heating problems when idling?

 

[Ray Neudecker]

Re: 70hp Over Heating

Not to my knowledge. Basic trouble shooting of the cooling system from the water pump on will be necessary to cure the problem. If the impellor has not been changed in 700 hours, I would start there.

 

[CaribouHills]

Re: 70hp Over Heating

I have changed the impeller, pump housing, left the gasket out just below the pump housing to get a little more compression on the impeller. Removed and cleaned the water jacket. Blew compressed air through the cooling system. Changed the thermostat after drilling a small hole in it to let a little more water by-pass. I plan on checking the head today. Any suggestions would be more than appreciated.

 

[Ray Neudecker]

Re: 70hp Over Heating

The poppet valve and seat would be the next thing I would check. Disassemble and clean the plastic valve and the rubber seat very carefully. I would also put the gasket back on the water pump. If the pump does not seal correctly, it will cause the problem. The poppet valve not sealing good or a water pump not sealing correctly will either one give you the symptoms you are describing. When you have the pump body off place on a flat surface to be sure it is not warped any. I use white lithium on the o ring in the pump to hold in place while assembling. Silicone and similar gasket materials often will often keep it from sealing. Hope this helps.

 

[CaribouHills]

Re: 70hp Over Heating

Ray, thanks for taking the time to reply to my posts.<br /><br />What and where is the poppet valve on a 70hp two stroke?

 

[fmenezes]

Re: 70hp Over Heating

I'm having the same problem as Caribou. What's a poppet valve and where is it located?

 

[fmenezes]

Re: 70hp Over Heating

Originally posted by Ray Neudecker:<br /> The poppet valve and seat would be the next thing I would check. Disassemble and clean the plastic valve and the rubber seat very carefully. I would also put the gasket back on the water pump. If the pump does not seal correctly, it will cause the problem. The poppet valve not sealing good or a water pump not sealing correctly will either one give you the symptoms you are describing. When you have the pump body off place on a flat surface to be sure it is not warped any. I use white lithium on the o ring in the pump to hold in place while assembling. Silicone and similar gasket materials often will often keep it from sealing. Hope this helps.