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Davey1
09-06-2008, 10:11 PM
Draining the cooling system
We have a 3 litre Mercury inboard, Alpha stern drive, 5 months old. I was just wondering whether anyone with a similar setup uses the hoses beside the engine to drain the cooling water out of the block & exhaust manifold after each use? The boat is operated in salt water so I flush the motor every time with fresh water as advised in the manual but do not drain the cooling water.

Trouble is when we got home & parked the boat in the garage after our last outing I noticed the exhaust outlet down near the leg has dry rust marks around it like it has been blowing out rusty water & the thermostat appeared to be stuck open, engine was not heating up while we were out on the water. Sounds like the cooling system has rust in it & the thermostat might have seized. The Mercury manual says to only drain the system for extended storage or if freezing temps are expected. It was only about 4 weeks between outings.

Going to book it in to get checked out but just wondering what you guys normally do?

curiser
10-06-2008, 07:28 AM
I have a 3 litre mercruise and wash it as you do. I have asked two dealers about the blue hoses and was hold I did not have to drain the water from them, hope they a right. see what they tell you.

bastard
10-06-2008, 08:47 AM
Its better to leave the engine full of fresh water, this stops air from getting to it and this will slow the rust down.

Davey1
10-06-2008, 07:59 PM
Thanks guys, its booked in to get the thermostat looked at tomorrow. They said definately leave the water in it.