Yamaha 25hp thermostat

[zenostone]

Howdy. Just changed my water pump and thermostat in a 1997 C25. Initially I had no water out the pisser; long story short - I tested the thermostat and it isn't opening until 160 degrees. I'm too much of a wuss to let it run that hot. My manual says it should open between 110-140 degrees.

My question - is 160 ok or too hot for the motor?


Thanks in advance.

 

[99yam40]

Re: Yamaha 25hp thermostat

It should start opening at about 120 and be full open at 140.
Is that the new one or the old one?
If it will not open until 160 then it is not functioning properly is my thoughts

The thermostat opening has nothing to do with the tell tail water flow, water comes out all the time.

 

[zenostone]

Re: Yamaha 25hp thermostat

The thermostat is new. With it installed there is no flow - uninstalled water flows fine.

Thanks.

 

[99yam40]

Re: Yamaha 25hp thermostat

All water cooled motors need their thermostats in place to act as a restriction to force the cooling water to circulate properly to all parts of the motor. without it in place there will be hot spots in some areas and the motor itself will not stay at the proper temperature for burning all of the fuel efficiently in the cylinders. Some have installed restrictor plates(washer with a proper sized hole through it) to act as a restriction, but I recommend putting a working stat in where Yamaha designed it to be.
I personally have never seen a motor that the tell tail was dependent on the thermostat to open before water would flow out of it.
But I have not seen all of the different motors out there

 

[zenostone]

Re: Yamaha 25hp thermostat

Yep, I think I have a plugged water jacket somewhere. I'm going to try low pressure compressed air and perhaps white vinegar to solve the problem.


Thanks for your help!

 

[Peter16]

Re: Yamaha 25hp thermostat

I personally have never seen a motor that the tell tail was dependent on the thermostat to open before water would flow out of it.
But I have not seen all of the different motors out there

USA built Merc 9.9/15hp are just 2 that i know of. Tell tale hose runs directly off the thermo housing cover.