89 Mariner 40HP Magnum over heating

[Deleye1]

Does a 89 Mariner 40HP Magnum SN OC186625 have a thermostat? It is a 4cylinder 2 stroke

 

[Harry B.]

When's the last time you serviced the impeller?
Can you see water coming out of the motor?

 

[racerone]

No thermostat shown on these I think.-----Do a compression test if it overheated.-----Replace impeller.

 

[Harry B.]

I always wondered without an answer how do some motors get away without a thermostat?

 

[Deleye1]

Thank you both for your replies. I have changed out impeller and the water out of tell tell was a little more than before. It still runs hot, if you rev motor up you would get more water out and it wouldn't run hot checked hose to see if and junk was stuck nothing there. I took water pump and impeller off put a new water pump gaskets the whole nine yards. Took it to the lake and running across the water it runs hot. I can just idle around and it runs normal temp to a little hot.

 

[Harry B.]

They run pretty hot normally.
You've checked off the items I would have done to assure the water flow through the motor short of putting a high pressure spray nozzle into the pipe coming off the impeller but you may have already done that.... of sorts.
They do have indicators to determine the temperature they are running per old manuals to assure the are not running "too hot."
Iim sure there better ways than putting a chalk or wax mark on the motor to see if it melts off or not nowadays, but they do run pretty hot.

 

[Deleye1]

Hello All

Update on over heating. I started over and replaced all gaskets and parts on water pump. also back flushed the motor. To off cooling jacket and plate replaced gaskets. The motor is running cooler but it will eventually run hot. I is like air is getting the flow of water. Sometimes it flows then spits sometimes it sprays mist then steam. Is there any where else that it may be pulling air from?

 

[racerone]

The fitting where water tube enters the powerhead has a grommet.----Checked that ?----These motors run fairly cool.----Tell tale should never be hot.----Are you testing with boat launched or a test bucket ??

 

[Deleye1]

I was thinking it to be a grommet or some type of seal where tube enters the powerhead. It seems the only way to tell is take powerhead of to see unless you know a better way that would be awesome.. I have checked in a lake after replacing everything. Since it doesn't have a thermostat my thought is there should be a hard constant flow from the pee hole but like I said it isn't. There is always some amount of air that comes through