Cold engine temperature issue

[GrtLkBtr]

I have a question about my engine temperature. I have had this boat now for six years, never have I had a different reading on the temperature gauge other than 170 degrees once the engine has warmed up and we are under way. This weekend, I happened to notice the gauge was at 130 and I had been at wake speed for nearly a mile. This was plenty of time to get the 170 degree reading. I thought to my self, crap the thermostat has stuck open. I went to the get one, the guy at the counter (who is also a mechanic) said why do you want to replace it if it is only running cool and not overheating? Ummm… I said , "I dunno? Maybe because it isnt right?" So.. he could not find a 160 degree thermo only 140's (he said there isnt a 170). SO, My question 1) Is this guy right?? 2) If I go against his suggestion and replace it, is a 140 degree thermo gonna be a problem. By the way, the engine is a 1995 7.4 Bravo carbureted. Any thoughts?

 

[BonBini]

Mine has a 140* in it. Temp gage runs 145*. Seems to be fine for over 20 yrs.

btw: the parts/mechanic guy sounds like an idiot. I'de call anouther source and see what they say...

 

[GrtLkBtr]

Thanks Ron. I still think I will be changing it out, but just wondered the implications of "running cold". The guy did ask if the engine was running bad, as if there wasn't proper mixture because of the lower temperature before he suggested not changing it. I did run it on the lake, full plane for a good period of time, keeping my ears open for anything different. Nothing but the gauge being a bit lower. I know there isnt much difference from 170 and 130 but what is odd is the fact that suddenly it is different. Thanks again

 

[dicor]

I would change it just to verify what went bad. Maybe it's the temp sending unit or the gauge. The thermostat is the logical place to start.

 

[BonBini]

“Running Cold” You run a better chance of cold fouling the spark plugs when doing a lot of idling or slow running.

160* sounds like the stat you were running and is probably an all around good temp.

 

[GrtLkBtr]

That might be true about fouling the plugs, but it doesnt (right now anyway) seem to run rougher at idle. Yes, I do think the 160 would be the right one. One thing that I didn't think of, for a verifacation of the actual temperature, is to turn on my cockpit heater and feel the air coming out. I will try that next, but I will change the thermo out before too long. I will get back to you all as to what happened. Thanks!

 

[GrtLkBtr]

Just an update. I did check the cockpit heater temp, and it was cold. I figured just to change the thermostat. I got a 160 degree and changed it out with no problems. Easier than I anticipated. The engine warmed nicely to 170 again and I am happy. Case closed. Thanks for all the suggestions.