Re: 18-20-25 Fuel Diverter Cylinders run warmer?

[johnyrude200]

Ill post a pic of the 3 spots I spend the majority of time on with the heat gun for all motors across the board tomorrow. If anything, I almost never look at the cylinder heads but focus on the starboard side cylinders (unless its a 9.9/15, where the exhaust is on that side) and thermostat orifice. With 4hp motors, the head will be 180-220 degrees, yet the cylinders will be 85-90. I will say Ive dealt with a few motors where that t-stat orifice isnt giving an accurate reading because the cylinder head orifice leafing into the thermostat bypass is occluded or plugged.

Recall our phone conversation from 3 months back with that 20 where the tap broke off in the cylinder head screw hole? That was a great motor, but that 1/8th inch cylinder passage was plugged, so the motor couldnt be run more than 60 seconds before the heat went too high. Yet the blubber hole showed water pumping like a hose.

Personal Story. The reason I’m so anal about cooling systems is because my 2nd motor, ever, was – ’69 johnson 25 that I seized 4 times due to an overheat. I melted the top piston and it still started on the 1st pull but had no top end after 5 seconds. I still own that block, but the other 95% had been repurposed (now that I’m turning wrenches full time.) The local dealer screwed me at least 5 times to the tune of 1,500.00, which is why Im in business now.

As usual, Im just looking for the best way to evaluate motors to insure they are ready to be put back into reliable, regular service. As said in Wayne’s World…IM NOT WORTHY! Here to absorb as much knowledge as possible.

Thanks again guys.