I have twin 3.7's and what you describe is a common problem for these. The
leak in normally between the
manifold and reservoir. It usually means that you have to
replace the reservoir and the gasket. If you pull the #4
plug you will probably see that the piston in that cylinder
looks very clean on top. That is because that is the first
cylinder it leaks into. Mine broke the piston in half before
I paid attention to it. You might want to check it a little
sooner to save LOTS of money.

Terry
"Ree-Yees" wrote in message
news
Two minor prods with the 1987 Sea Ray. It has a 3.7 liter mercruiser I/O
engine with a closed coolant system. So I have a antifreeze tank,
overflow
tank, and a big cylinder on the side that antifreeze and water runs
through.

To keep the antifreeze in the overflow tank between the add and full
lines I usually have to add in one to three cups of coolant into it each
time I take the boat out. I can start the boat up and turn it on and off
and run it for a while in the yard and the coolant amount stays the same
and
no smoke comes out the back.
When I take it out on the lake and I turn it off in the water and let
it
sit there for any amount of time more than a minute or so, and then start
it up a bunch of whitish smoke comes out of the back appearing to come
from
the exhaust. It smells like exhaust with a hint of antifreeze. This is
where I am losing the coolant, but I dont know where its leaking at. Oil
is
not milky and this problem has stayed consistant for the whole summer so
far.

The second problem that may or may not be related to the first problem
is that I have a leak in hte boat. The leak is down at the bottom of
where
the outboard peice comes through the transom. The leak is not big enough
to
make the bilge pump run for for a little bit every once in a while, but
water is definitly coming in. To get to whatever is leaking the outboard
peice is going to have to come off. How much to places usually charge for
such a task?

Thanks for any info you got!
Cameron