took new boat out today,has 5.7 merc....it was running a few above170 deg when running WOT....i thought this was a little hot. and when got that hot let off a little. what temps should they run at?
If you're running a 160 degree thermostat...that would be a normal reading. If using a 140 stat, it is either not opening all of the way, you have other system obstructions, or your temp sending unit or dash gauge are giving false readings.
that seems a little high. mine was doing that, then it started climbing higher at idle, enough to trip the alarm. i didn't run the boat that day, pulled it back out of the water and rebuilt the raw water pump.
after i fixed the pump in the lower unit it never goes above 130 degrees, even at WOT.
As stated, 170 to 175 is quite normal with a 160? thermostat installed. As far as where the impeller is, who knows, all you have said is it's a 5.7 Mercruiser. Nothing about year, model number, type of drive or anything.
5.7 engines have been used since 1969 and they have changed a lot in that time.
To check the raw water pump, you're going to need to remove the lower unit of your drive and pull apart the pump housing to inspect. At that point, it might be worth it to just replace the impeller with a new kit. Do a search on here and/or youtube and you'll get plenty of instructions/how to's for doing it. It's not a bad job, just take your time and be thorough.
To check the raw water pump, you're going to need to remove the lower unit of your drive and pull apart the pump housing to inspect. At that point, it might be worth it to just replace the impeller with a new kit. Do a search on here and/or youtube and you'll get plenty of instructions/how to's for doing it. It's not a bad job, just take your time and be thorough.
I agree it is not a bad job. Toughest part is putting the unit back in as it can be quite a bear. I have used a floor jack to help, but having someone around to assist is also good. Make sure you have the little rubber o-ring in place for the oil passage-way when reinstalling!
As stated a couple of times already, 170 to 175 is normal for a raw water cooled engine with a 160? thermostat. If the outside temp and the water temps are really high you may see up to 180?. But, if it goes higher than that, you have a problem.
