This may be a dumb question,but.....

What temp is considered " overheating" on a 3.0 Mercruiser? The reason I,m asking is that I,m replacing the exhaust shutter on my 3.0 and when I went to pick up the new shutter the guy said I must have overheated it at some point. I did just about peg the temp about 6 yrs ago due to an impeller failing,but like I said,that was at least 6 yrs ago.Since then I,ve had the temp run up near 200 due to another impeller and then before that I had serious weeds around the prop. Both times I shut down and took care of the issue and really didnt consider 200 degrees as "overheating", but maybe that is? What temp is considered overheating? Just curious.. thanks!

Re: This may be a dumb question,but.....

As I understand it, it is not necessarily "overheating" that takes out the shutters, it is lack of water flow cooling the exhaust. Even though the two go hand in hand, at some time your water flow may have been reduced to the point that the uncooled exhaust cooked your shutters, even though the engine did not overheat too bad.

Re: This may be a dumb question,but.....

that seems to be hotter than it should to me, my merc. (even though its a v8) never gets above 165* even when towing two tubes or running 40 mph for 20-30 miles. I dont think 200 is over heated but it is hotter than the unit should typically run. If I get close to 200 I'm starting to get real concerned because something isn't right...

Re: This may be a dumb question,but.....

The qustion is What temp sets off the Alarm beeping sound? That would be the tell sign of over heating per spec on engine for the 3.0. I'm not sure even what temp that is. Anybody now whar temp mark sets that alarm off for the 3.0??? Mine runs about 170 ish to 175 ish depends on the upper incline temp of water.

Maybe your thermostat is bad.

Re: This may be a dumb question,but.....

When I almost pegged the gauge about 6 yrs ago..the gauge was over 220 and if I hadnt caught a whiff of "hot engine" I wouldnt have looked down at my temp gauge to even notice anything wrong,so at that temp I didnt here any alarm at all. The boat has always run around 150-160 in normal conditions,but the 2 times I did get it up near 200 since,I,ve shut it off,let it cool and limped back to the slip and repaired what ailed it. So when the parts guy mentioned that I had overheated it,I was just wondering if I had ruined the shutter 6 yrs ago and its just been rattling around in there since,or if one of my excursions up near 200 degrees might have been the culprit. I guess the question should be.." at what temp is it critical to shut down" and what temp would you consider it safe to limp home at,if you can maintain that temp?