Another Overheating Question

[Frank1]

1990 100 HP Evinrude 4 cylinder<br />Get alarm 5 minutes after starting. Have read where air gets trapped in Tstat housing not allowing water to reach Tstats. Vent hole plugs not allowing air out fast enough. Have read where some people drill small hole in poppet valve or Tstat. Will this do any harm? <br />Thanks in advance!!

 

[IndySpecialty]

Re: Another Overheating Question

Frank1: Before you do anything are you sure its a overheat alarm or is it an oil related alarm, I have never had to drill a hole to keep the alarm off, the only thing I have done is drilled the small bleed holes in the t-stat & pop-off housing just a touch bigger only because they were plugging all the time, not for any other reason.

 

[Frank1]

Re: Another Overheating Question

Its a steady alarm. Which I understand is a heat issue. If I touch the top of cylinders they are hot. Once the tstats start working you could feel the difference. Slightly warmer then cool down. I put a .060 hole in each poppet. I dont think it will do any harm but I am not sure. <br />Thanks for responding!

 

[seahorse5]

Re: Another Overheating Question

The crossflow V4 thermostats are known to "stick", especially if the small air bleed and drain hole gets plugged. The water then stays in the aluminum housing and corrodes the brass t'stats. The factory now uses stainless steel ones that last a lot longer.<br /><br />Usually, filing 2 small notches 180 degrees apart on the white pressure relief valves, helps with bleeding the air out on startup, and draining the housing on shutdown. Position the notches facing up and down for best results.

 

[EVMIII]

Re: Another Overheating Question

Frank,<br /><br />Is the engine overheating? I recently discovered that on my Johnson 225 (1989) the water pressure and overheat alarm were the same. I was getting the alarm, but was not overheating. I changed the water pump (not just the impeller) and have not had a problem since. I'd definetely change the water pump and the thermostats before I drilled any holes. Good luck.

 

[Solittle]

Re: Another Overheating Question

Where is this drain/bleed hole? Anyone know if the 1988s have this?<br /><br />I pulled the thermostat assembly off of my 1988 engines today and would like to do "whatever" before installing the new thermostats and putting them back together. <br /><br />Pain in the butt removing them but got them out OK.

 

[IndySpecialty]

Re: Another Overheating Question

Guard Bum: That is a great point to all, far to many people go the cheap route & just replace the impeller, these housing get warpped & leak out the sides & do not provide enough volume or pressure, its best to place the complete assy. My 2 cents.<br /><br />solittle: Yes your s should have the same set-up, just look close at the piece that held the stats & pop-off's the little hole are probably plugged & you can't see them. a parts book break down will give you a good look at what they look like & the little tip about filing a little groove is a great idea to help get the air out.

 

[Solittle]

Re: Another Overheating Question

This is to indydan - Found the vent hole - thanks. Mine were relatively clear which is remarkable for 14 year old engines that run in salt water. Guess the fresh water flushing pays off.<br /><br />Do you have any tips on how to keep the assemblys together when I go to reinstall them on the motors? e-mail direct if you prefer (hw8478@bellsouth.net)I did not pull the powerheads or drop the pan at the base of the engine. I removed the rear plastic shell to access the two outside bolts on the thermostat housing. I am concerned that something will move out of position as I try to fit the assembly back and get it bolted down.

 

[Frank1]

Re: Another Overheating Question

Installed new tstats (stainless) and drilled .060 hole in each poppet. No alarm now. From my understanding air getting trapped in housing prevents the water from reaching the tstats. Which of course prevents them from opening. <br /> The spring tension on those poppet valves seems to be pretty strong. Is there that much pressure created to push them open? <br /> Appreciate everyones suggestions.