Evinrude 115 operating temp on muffs

[kcm805]

I recently picked up my first boat, a 19ft 1979 glasply runabout in amazing shape from the original owner really cheap (trailer needed work and boat needed a good cleaning). Has not been on the water since 2013. Outboard engine is a early 80s evinrude 115 v4 crossflow with low hours on a rebuild. I was testing it in the driveway on the muffs to make sure everything is all good and the temp on both cylinder banks climbed beyond 190 in about 15 min at idle (measured with IR thermometer). Shut it down and pulled the thermostats and they were really corroded from salt, stuck closed, and full of sand. Cleaned everything up, got new thermostat kit (tested on stove first and they worked perfect), fired the engine up and now after 15 min at high idle on the muffs the head temps barely got to 100 deg. Is that normal? Could the water pressure from the hose be forcing the spring loaded bypasses open? I am getting solid telltale flow (though cold) and the only warm water is from the discharge port aft of the water intake.

Replaced everything exactly as repair manual stated (and took it apart a second time to confirm), no leaks so not sure what's going on. I have yet to take it out on the water as I am waiting on a few parts for the trailer. I assume under load it will get hotter but i didn't expect it would stay that cold on the muffs.

 

[oldboat1]

Think you are fine. Incoming water temp at hose is probably around 40F.

 

[havoc_squad]

At full operating temp, the top of the cylinder heads (looking from the sky down at the cylinder head should reach between 140 degrees Fahrenheit (+/- 15 degrees F)

Hopefully by high idle you mean no more than 1500 rpms.

That sounds a bit colder than what it should be, and I don't believe the relief valves kick in until the engine gets into the +2000 rpm range.

I'm sure some of the OMC techs can say whether this is a bigger problem or not. I would definitely be concerned about a recently re-built motor that needs break in not reaching full operating temperature.

My questions would be:

To avoid assumptions, what parts were kept and what was replaced when you did the thermostat housing?

 

[kcm805]

I should have specified. The motor was rebuilt about 10 years ago. it was used for a few years (~200hrs) then parked and started up yearly since 2013. I assume to keep things lubricated and avoid rusting/seizing rings/bearing. No way to verify, going by the prior owners word and paperwork for the rebuild.

As for what was replaced, it was an entire kit. 2 of each: thermostats, springs, gaskets, cork ring for the thermostat, plastic bypass piece (not sure what they are called, the white parts under the springs), and rubber grommets that go with the plastic pieces.

High idle was using the warm up lever on the control panel and engine was in neutral. Tried both ways (high/fast idle and normal) though didn't seem to make much difference.

 

[Fed]

Could the water pressure from the hose be forcing the spring loaded bypasses open?

I believe that's the case.

 

[oldboat1]

Test it in the lake. Monitor with that IR thermometer. (Running on muffs is never a good test of cooling systems.)

 

[kbait]

Oldboat Is 100% correct. Lake or deep-enough barrel is the only conclusive test.