overheating 4D61

[Cturtle]

I have changed the thermostat, the impeller, and water is coming out the exhaust okay. She overheats over 3000 rpm. I am now going after the exhaust elbow. It has never been done (1985) 27FC. I am afraid of breaking off bolts removing the elbow. Any advice?

[WillieC]

Kroil, heat, time and patience. Rinse and repeat. Good wrenches, protect your knuckles. If you have nuts on studs, you may want to get a nut splitter, or chisel them off. Try not to bust the studs. If nothing is budging, walk away after re-kroiling. Haste can be your biggest enemy.

(You asked for advice. I, myself, usually get in too big of a hurry and end up busting more stuff than necessary.)

[RobS]

As Willie said and add to that a 6-point box wrench

[DCatSea]

Have you tried removing and flushing the heat exchanger and cooling system. Mine was pretty much a clog-fest, but a Barnacle Buster bath did the trick for me. Removing the HX and giving it some internal TLC also enables you to change the internal zincs. My 4D61 has run cool for years.

[Cturtle]

Have you tried removing and flushing the heat exchanger and cooling system. Mine was pretty much a clog-fest, but a Barnacle Buster bath did the trick for me. Removing the HX and giving it some internal TLC also enables you to change the internal zincs. My 4D61 has run cool for years.

Thank you all for your responses-
I got the elbow off with ease to my surprise. It all looks good??? Next project is new heat exchanger. I opened it up with a coat hanger the beginning of last year, thought it was pretty good. So far I have done impellor, thermostat, checked the elbow, good flow out exhaust.
Should I replace the temp sensor or gauge? The alarm does come on.

[Carl]

Have you checked all those components with a temp gun while running?