1989 150hpCooling water pilot hole, Water Temp.

1998 Yamaha C150TXRW
How hot should the water coming from the cooling water pilot hole be after the engine has warmed up (2 to 3 minutes) and has been run for 20 minutes? I thought it should be approximately whatever the thermostat rating is unless the pilot hole on this engine is fed from the flow before it passes thru the engine/head water jackets ahead of the thermostats. The thermostats are opening at the set temp...I tested them using a pot on the stove with a digital thermometer. The bypass valve and spring were replaced also.

The engine runs great, does not overheat and the flow from the cooling water pilot hole is strong at idle and stronger at 4000 rpm. The water coming from the pilot hole on this engine never heats beyond the lake water temp......Any ideas?

Re: Cooling water pilot hole, Water Temp.

Mine is warmer than the water that goes in, but it never gets hot.
I would guess it's about 100 degrees or so.

Re: Cooling water pilot hole, Water Temp.

Depending where your tell tale is fed from it will be a little warmer or a little cooler than your thermostat temp range.

If it's being fed from the thermostat housing (at the top of the block), it will definately be cooler than if it's fed from further down the block or off of the exhaust cover (after the water has absorbed heat from the powerhead to a greater extent than at the top of the block).

Most motors, at operating temp, will be running in the 130-160'ish range, so once warmed up your stream should be "warm", but not so hot that you can't keep your hand under it - should feel like a "hot shower" - on the other hand, cold is NOT a good thing - a motor running too cold is almost as bad as running too hot...

Re: Cooling water pilot hole, Water Temp.

Thanks for the input.