White Smoke coming out of exhaust holes

"I have a 1990 Mercruiser Alph

"I have a 1990 Mercruiser Alpha 1 3.0 enginge. When i turn it on, it starts to overheat and then i get white smoke coming out of the exhaust holes and thru the propeller. Otherwise, the engine still runs and sounds good and no smoke or knocking seen or heard in main engine compartment...please help, what could it be?"

Is it FWC or RWC?
Is it still

Is it FWC or RWC?
Is it still cooling properly?
Rod

"I bet it's the OD L/U imp

"I bet it's the OD L/U impeller and/or the raw water pump if it's FWC. The white smoke is steam from what little water is getting to the block. But, if the OD was in the up position over the winter, the water supply hose may have a kink set into it. But, that would also cook the impeller.

Guy"

Thanks for getting back..first

Thanks for getting back..first off..i'm new to some abbv. what is FWC AND RWC? My boat has been stored for the whole winter..with my OD in the up position. I believe i use the water i'm in to cool off my engine so its not a closed circuit. Like i said..it blows white smoke out along with some spurts of water out from the exhaust holes. Could it also just be the Temp.thermostat? how hard is it to change out the Impeller along with the water pump?

"Jerry;
FWC is fresh water co

"Jerry;
FWC is fresh water cooled and RWC is raw water cooled. The latter is the most common, where your outdrive pumps sea or lake water up into the engine block for cooling and expels it out with the exhaust. FWC had a heat exchanger about 4" diam and about 20-24" long mounted near the front of the block thru which lake water is pumped. The lake water cools a water-glycol mixture which flows thru the block in a closed loop, much like a car engine.
If you plan to service this yourself you first need to get yourself a Seloc or Clymer service manual and study it hard. It will tell you what you need to know.
Rod"

Thanks Rod..so u dont think it

Thanks Rod..so u dont think it could just be the T.Thermostat? whats the average temp. my engine should read once warm and running?

Warmed up it should be about 1

Warmed up it should be about 160 give or take. That temp should not make steam or smoke. You will get some vapor but that is it. Since a T'stat is cheap why not change it out? Can't hurt.
Rod

Rod:
What about a kinked wa

Rod:
What about a kinked water inlet hose in the OD? It seems that not much water is getting to the engine and what little does turns immediately to steam. Guy

"Absolutely Guy/Jerry; the imp

"Absolutely Guy/Jerry; the impeller, leg to transom, and transom to T'stat housing hoses all need to be checked for any obstruction, and good water delivery. Could not agree more!
A good test would be to temporarily disconnect the main supply hose at the T'stat housing and run it into a bucket. Start the engine for a few seconds (with a hose on the drive leg) and see what you get. At idle it should deliver something like 6-8 GPM.
Rod"