Mercruiser 228 got hot, but was it too hot?

[Josephmcg]

30mph and under temp stays at 140 the whole time, once I start getting up to 35-40mph the temp will slowly start to creep up, once temp gets to 160 I back off start going slower say 20-25 mph and it goes back down to 140. I can run across the sound for 10-15 min straight at a constant 25-30 mph and have no temp issues what so ever.... has me a little stumped, boat comes out of the water in 2 weeks, any helpful advice would be greatly appreciated thanks again guys

 

[Lou C]

What temp thermostat do you have in it?
Even if it's a 140 stat that is not really too hot, but will the temp keep rising to over 200 if you don't slow down? Older Mercs had a 140 stat but newer ones had a 160 stat.
Id look up how to do the raw water pump output test, take the thermostat out and make sure it opens all the way at the specified temp. Lastly Id make sure all the ports in the Thermo housing are open . Some Merc stats have check balls that can get stuck and not flow enough water.

 

[Josephmcg]

Yeah if I were to continue to drive temp would just keep climbing, I have a 140 tstat, or atleast I think I do, I can let her idle in the harbor in my slip to warm up and if I let her run a while she never goes past 140