Atomic 4 overheating

[kbgunn]

Thanks for another view CajunSpike.

If I'm understanding correctly, normal operation is to start a cold engine with this valve OPEN to bypass the engine block cooling passages. As the engine warms and temp rises, partially or fully CLOSE the valve to force water into the engine block passage. As part of final shutdown procedures for the day, turn the valve back to OPEN position.

This will eliminate the need for a t-stat altogether and the t-stat housing will be empty.

[Dave Neptune]

k, no need to constantly adjust. I never touched mine unless I saw it getting to around 130* then I would adjust closed a bit and look for why the beastie was running warmer.
Use a "ball valve" when you do install and try it at about half open. The ball valve with it's lever action gives a good visual reference as to how far it is open or closed. It will take a long time to warm so take her for a spin under load. After a half hour or 45 minutes the engines temp should settle~THIS is when you make your setting adjustment~ once set you will not need to touch except for minor adjustments as to seasonal water temp changes.

ALSO be sure the t'stat is REMOVED!

Dave Neptune

[sailr]

Hot running engine

I had an atomic 4 that ran hot. I tried acid flush and vinegar flush with little improvement. I finally pulled the head and discovered that all the cooling channels were blocked with some type of sedimentary stuff. The channel from the thermostat housing was affected also. I had to take a drill and actually rebore where the channels were blocked. It was easy to tell where the channels were by the change in texture from metal to rock like mess. Easy to see why the acid flush and vinegar flush didn't work. After I bored all the channels out I flushed the head with 6% acetic acid and made sure everything was open. I replaced the head with new gaskets of course and after reconnecting everything I fired her up and Viola! no over heating. If all the other efforts fail take a look at the head and the cooling channels there.
sailr

[joe_db]

You got some good advice.
I would get a cheap portable tach and find the true RPM. No way is any direct drive A4 getting 4,000 RPM. 3600 is redline!
Actually getting past 2400-2500 with a displacement hull is almost unknown.
Now for the temps......This could be trivial and it could NOT be trivial to fix. The gauge itself could be bad. An IR gun will work to an extent, but you need to know what to aim it at. Two good points are the thermostat housing and the temperature sender itself. Do not aim around the spark plugs or over where the valves are, it gets hot over there.
If the engine does overheat, keep in mind mud and biological debris exist in fresh water and iron rusts in fresh water too, just not as fast as in salt. There could be significant clogging in the engine.
As a *buyer*, I would be going OMG that engine is dead I need a big discount