Re: 81 Evinrude 140 HP overheating - W/New thermosat
Really, the engine should have a thermostat to run corectly! Taking out the thermostat is at best, a band-aid to a different problem!! If you are confident that the water-pump is operating correctly, it's probably the pressure relief valves that are sticking. You have two choises to overcome this problem. I've discribed it way back but I'll do it again. The pressure valves (2) are located just next to the two thermostats, just at the aft edge of the powerhead, in a not so friendly location. Often the valves get stuck in their rubber seats and prevent water from reaching the other side where the sensor side of the thermostat resides. Sometimes salt contributes to this sticking of the valves (and removale and cleaning is the only solution) and also slight modification to the valve so as to let some of that captured water seep to the other side of the valve may be needed if you choose to go "inside" the thermo covers! . Now, here is a quick fix that you may care to try, or not!!! This problem manifests it's self often if you just start up the engine and let it idle a while versus taking off and getting high rpms and hense more water pressure. The symptom is one head is "cool" while the other gets real hot! Big time, if you don't monitor the horn, the smell of melting wires, etc..... So, remember this, I will assume that the "tell-tail" is strong and one head was in-fact cooler than the other! So, we'll assume the water pump is in fairly good shape! (BTW, the only correct way to determine this fact is if you visually inspect the pump!!!) Anyway, This "trick" will probably solve your prob;em without actually taking a wrench and going into the motor. When you first start up this engine the next time, either on the flusher or in the water, flip the carb linkage roller (you can use the warm-up lever if you like) and give this engine some good high revs. Once maybe twice, as it sits there at your driveway or at the dock. We're talking some serious rpms!! The increased water-pressure(due to higher tpms) very well may "un-seat" the offending pressure valve so that it may/will work correctly from now on! (and hopefully, not stick again!).Moniter the cylinder head temp and if it still gets "frigg'n hot" to the touch, well, stop on the third try and again, get out the wrenches and have fun!! Now, before someone goes ballastic about "high rev'n" a fairly cold engine, which we all agree on is not really the "right" thing to normally do, Yes, we understand.. But we are trying to accompolish un-seating the pressure valves and one or two short "raps" will do no harm! If you don't like this "idea", then don't do it and ... get out your wrenches!! This problem manifestgs it-self more often in the spring after a few months of inactivity (the valves are held shut by springs) and one or two uses and fluctuations often help them becoming unstuck! Or, again, perhaps salt/minerala may have them suckers real stuck!! Good luck!! BTW, I've done this "trick" many times and have never had any adverse effects ie. rods busting through the side of the block, etc... but again, if it doesn't break free after the third "rap", go to Plan B.
