slightly overheating 502
 

One of the things I noticed when running the boat in Lake Tahoe in Dec (52 degrees out with cold water) was that one motor ran at 170 degrees and the other at 185 degrees. I asked the previous owner if this would be a guage, a impeller or a thermostat. He said he put a heat gun on both engines and they read the same temp.... He did not know. I suspect I need to do this myself again to see if this is an accurate reading. This boat has huge sea strainers and the amount of water passing through both looks the same.... Plus the water pressure guages both seemed about the same. Possibly the thermostat? Just what type and temp thermostate is put in these boat motors? A regular 160 degree or are marine thermostats different? Just what is considered overheating? I have seen complaints about 200 degrees on other boats.......... Is 185 high?

Your gauges could be off but either way that is good temps. 240 probs. 180ish all good. Enjoy the boat and dont sweat it until you see them erratic

I chased a similar problem once checked everything even the water hose at the transom found nothing.Turned out my gauges were 10 degrees hotter than the motor.I took readings with a temp gun right were the temp sender was and it was 10 degrees lower than the gauges.
Mine would also do it more when it was cold out I felt that the thermostats were not opening as fast as they should so I put 140 degree thermostats in.

He guys, thanks for the advice. Glad to hear that it isn't overheating. I will see about getting a heat gun and see what the temp is at several points on each block. I least this way I can find out if its the guage or maybe a thermostat that just needs replacing. The previous owner noticed it too - it wasn't normal to be that different from each other even if its only 15 degrees. I did read a long thread about some guy who paid to get his 454 rebuilt and demanded 30 over and found out it was 40 over when he had to tear it down because of some issues, including/because of running at 200 degrees. This got my attention because if 200 is bad, then I am getting close. I did not even know you could buy a 140...! So, what is the recommended thermostate? 160 across the board for all Chevy BB's?.

Assuming that boat motors are constantly being stressed, typical car/truck temps would seem high. Even 210 would seem high...