'83 Evinrude 115hp bizarre cooling problem

[ashedd]

I've done a lot of work recently on my '83 115hp evinrude that I got with a project boat purchase. I removed all the internal corrosion from the powerhead, replaced head gaskets and cylinder head gaskets. Replaced the exhaust cover gaskets, valve body and thermostat cover gaskets. As well as the valve body and thermostat cover themselves. And I of course replaced the thermostats, springs and valves. Oh and the deflector tubes in the cylinder heads.

The motor pumps water(all new impeller etc) great, and cools fantastic with the hoses from the cylinder heads to the valve body removed, the water coming out is lukewarm. When I install the hoses the left bank of cylinders stay cool to the touch but the right side over heats(too hot to touch). I take it apart and swap thermostats, same problem, left cool/right hot. Nothing looks out of place. Both springs and valves are free, all gasket material is trimmed up. The thermostat seals look fine. At this point the only way to keep the right side cool is to remove the thermostat. But I can't run with the left at the right temp and the right too cool. I was going to get a new thermostat but swapping them didn't fix it, and I tested them with heat and they both opened.

What's going on?

 

[interalian]

There are two tiny holes in the bakelite spacer for the thermostats. If blocked you don't get water flowing past the thermostat so it won't open. I've seen plenty of suggestions to hog out those tiny holes somewhat. I just did mine a shade under 1/8".

 

[ashedd]

There are two tiny holes in the bakelite spacer for the thermostats. If blocked you don't get water flowing past the thermostat so it won't open. I've seen plenty of suggestions to hog out those tiny holes somewhat. I just did mine a shade under 1/8".

I will definitely check that out. I'm not sure if I knew about them or forgot they were there... I burned holes in the old spacer with my oxy torch trying to get the bolts out, so this one is new. Thanks

I'm also running fuel from last year, maybe that's a problem too(In reference to my other thread).

 

[emdsapmgr]

Ashedd makes a very valid point. It's true. I'd be surprised if one of the two small holes in the valve body is plugged, since you say you replaced the valve body. Unless the replacement body was used and one side might have been plugged.

 

[interalian]

True enough, but a bit of crud could have made its way through and blocked the hole. The thermostat housing is a major pain to R&R...

My current rebuild is getting close to done and I plan to flush the block with the head-to-thermostat hoses off before buttoning it up, just in case something is dislodged and plugs the bleed holes. Housing is bad enough to R&R on a flat back, but with a bubble butt exhaust, it's even more a PITA.

 

[emdsapmgr]

You are lucky that your 1983 engine is a flatback.

 

[interalian]

One question: how are you testing it? Tub? Muffs? If tub, how deep? Really sounds like an air bubble at the highest point.

About 10 years ago I drilled and tapped 1/8" NPT holes at the top of the cylinder head water covers and fitted thermo senders and a switch to monitor Port or Stbd (usually left it on Stbd since that's the more likely candidate for bleed problems). Might also tap another spot next to them and run pissers off the top of each cover, which should eliminate any air pockets. Or am I on crack?

 

[ashedd]

I think there is a lot of sealant on in that area, I'll go get new gaskets and check it out. I'll probably forego the sealant this time.

 

[ashedd]

I cleaned/cleared any suspect sealant, drilled out the hole mentioned above. Right side still gets hot. I just pulled the thermostat for now. I can't keep screwing with this, I'll just run without a thermostat on the right side.. If it is an air pocket as mentioned earlier, Maybe it will work it's way out over time. I dunno.

 

[ashedd]

Motor is running fine in the water.. some point this year I'll try to pop a thermostat back in and see what happens.