Should I Re-torque Cylinder Heads After Overheat?

[Benjaminlbarker]

I've got twin Mercruiser 470's (1986 Mercruiser 190) I've been dealing with. I know... During testing and trouble shooting these motors have gotten to 220 degrees max, read from an IR thermometer pointed at the sender. Been having problems with the temp gauges and other some accessories so it's hard to see the overheat coming. One engine (starboard) is a fresh rebuild and has already been re-torqued after the initial run, the overheat was about a half hour into the run after that. It got to about 210. The port engine has about 400 hours on it and overheated to about 220-230 due to a bad riser/reservoir. So should I re-torque the heads? I've gotten about a 50/50 response from my research thus far from various sources, marine and automotive. I would love a definitive answer from people who have real experience with this. Thanks!

 

[Eric 3.7LX Alpha 1]

The gasket may already be blown out and might be futile. You certainly could try but may be too late. Have you resolved the overheating yet?

 

[stonyloam]

Do a compression check.

 

[saltybutwet]

IMO I would do a cylinder leak down test on each cylinder, and that would show if you have a warped head, blown head gasket, leaky valves and so on, then if all seems ok then I would figure out what is the root cause of the overheat issue, fix it, then re-torque the head, fire it up, and keep an eye on the temp

I am no professional Marine mechanic, just a DIY mechanic, and this is what I would do, if I had that issue or issues