Engine temperature runing on muffs

[jimrockireland]

I have an 1983 MCM228R with a MC1 sterndrive. I have done extensive repairs on the engine and sterndrive and am now running tests on it with the boat out of water using the muffs on the sterndrive, I'm not sure what temperature the engine should run at, but I am seeing the thermometer climbing to about 190F after 15 minutes. I'm wondering if this is normal and should I expect the engine to run cooler when in the lake? I'm also wondering if I should remove the thermostat in the engine since I don't see much use for this in a boat?

 

[Alumarine]

190 is too hot if it's accurate.
I believe it should be 140 if raw water cooled or 160 if freshwater cooled
You need more flow on the muffs or there's a blockage.
Thermostat is important, that's why it's there.

 

[Scott Danforth]

On muffs, you are running a 5/8" or larger hose with the spigot fully open and the motor below 1500 rpm, correct?

 

[alldodge]

Where is the water coming out that the muffs is letting in?
Are you sure you got the water tube inside the drive back in the correct place, after replacing the impeller?

 

[jimrockireland]

I'll check again that the water pump tube is inserted in the upper water tube. I was not running the 5/8 hose at wide open capacity, but I can try and increase that. The rpm's were idle at 850 rpm's. I took the lower unit off to replace the impeller. While off I did a few tests. I ran the hose into the MCM228R inlet hose and saw water coming out of the back of the engine. I ran the hose back through the sterndrive (reverse of the normal water flow) and saw water coming out of the sterndrive where the muffs go on. With the muffs on I see some water coming out of the back of the boat, but not a lot. It would be nice if I'm just not putting enough water through the muffs, but even at the water rate I'm using I see water pushing out through the muffs and not entering the sterndrive.

 

[alldodge]

I would suggest, put the muffs on. Remove the hose coming from the drive to the thermostat housing. Turn the water on and then start the motor and see if water comes gushing out

 

[enginesilo]

I experienced something similar a year or two back. The engine wasn't pushing out nearly enough water from the exhaust/bell housing while on muffs and the temp would climb. After lots of guessing it turned out to be the water impeller in the outdrive (alpha 1 gen 2). I had changed it the season before but for whatever reason the replacement went bad quickly. After replacing it there is a lot more water exiting while on muffs, and the boat runs cool as a clam as it should.

 

[Scott Danforth]

I was not running the 5/8 hose at wide open capacity, but I can try and increase that..... With the muffs on I see some water coming out of the back of the boat, but not a lot. It would be nice if I'm just not putting enough water through the muffs, but even at the water rate I'm using I see water pushing out through the muffs and not entering the sterndrive.

use duct tape and tape the muffs to the motor if your muffs dont fit properly. however you need to turn the spigot fully open to get all the water you can.

your impeller pumps about 10 GPM a few hundred RPM's above idle (about 20 gpm at 3500 rpm). that is one 5 gallon bucket every 30 seconds at about 1000 rpm. your garden hose will not fill a 5 gallon bucket at the same rate (unless its a short 25' or less hose).

 

[Bababouy]

Is 140 mandatory for salt water? My gen2 runs at 175.

 

[Scott Danforth]

Is 140 mandatory for salt water? My gen2 runs at 175.

Depends if the motor is carburetor or fuel injected, with or without a heat exchanger