Volvo md7a overheating, temperature fluctuating
Hello all, hoping to get some input on my latest volvo md7a woes. This is a 1979 MD7A raw water cooled volvo. Here is what is going on and I've tried
When I bought it the flowed almost no water and overheated.
1. pulled exhuast manifold, cleared blocked water passages, flushed out engine with hose.
After this it flowed a good amount of water but temp would creep up and would overheat if I ran it over 1500 rpm for any length of time. Going to lower rpm would bring the temp back down. Water felt cool/luke warm.
2. removed thermostat.
Ran cool, barely moving the temp needle off the peg. Water coming out the exhaust felt warmer
3. put in new thermostat and now it gets hot, just starts to overheat then the temp goes back down to 1/3 (well into the green) then back up etc etc. Sticking my hand in the water coming from the exhaust, it feels like the temp matches what the gauge says (very hot when it's near/just in the red, warm when it goes back down to 1/3)
Did I buy a bad thermostat? I don't have a thermometer to test it but I may have to go buy one. I cleared all the passages in the manifold and water flowed through everything I could find. The transmission leaks water at about 1 drop/ minute, but I don't think that's affecting this. Any experience with thermostats being bad from the factory? Other ideas?
Cape Dory 28 "Dulcinea"