RMM

Question, what is the proper operating temp range for a RWC 1988 Merc 7.4L/Bravo I? Noticed yesterday that it was running up to around 190-200 deg at about 3400rpms. Don't rember it running this hot before, but it was very humid and around 95 deg air and around 75 deg water temp on the Chesapeake yesterday. At idle or below 3000rpms drops right down to between 140-160 deg.

The impeller is brand new and seems to be pumping water fine. Main concern is b/c had an overheating problem at beinning of summer where engine ingested water, b/c intake was crimped off. The problem was caused by the marina and concerned about further problems, ie head gasket. Thanks

RMM

btt

euby

mine runs consistently at 160 degrees...always has. mine is a 96 7.4mpi with bravo 3 but should be the same i would think.

euby

are you running a t-stat? could be faulty if you are.

RMM

How do I test the T stat?

kk1118

I have had a problem similar to yours. Turned out to be in the intermediate housing where the cooling hose comes into the boat. Mer-cruiser pushes the hose thru a hole in the intermediate housing (both inside and out towards the outdrive) and this hose is held in place be a plastic "keeper". The inside keeper on mine (under the fitting on the intermediate housing that the cooling hose to the water pump connects to) "melted"? almost closed. At low rpm's all was ok, any time rpm's went above @ 3200 temp would climb. Inside is easy to check, outer one you need to pull drive.
Hope this helps.

euby

get some water hot on the stove and drop the t-stat in and see if it opens. if you have a thermometer you can adjust to the right temp and drop it in just to check correct degree. what kk1118 said makes since but i don't know how it could melt unless you've had some serious overheating problems.