mercury 15hp thermostat housing

[beerbelly]

hi I pulled my outboard out of hibernation this week and in a barrel of water it fired up 3rd pull I was pleased .anyway I noticed while checking it over the join around the thermostat housing had crystalline deposits all around and a slight line of the same running down wards im assuming its salt deposits and the housing has a slight weep .what I need to know is should there be a gasket or is it just a face fit with a smear of rtv I am going to change the stat while its apart.its a 2005 mercury 15 2 stroke. many thanks

[Max...]

It has a paper gasket, when I did mine I used the housing as a template to cut one but you could get the genuine part of course.

[Fenlander]

Of course unlike a car cooling system it isn't under pressure so while a tiny weep like you have is unsightly and could lead to localised cosmetic corrosion of the engine over long periods it's not crucial to the running of the engine.

So for that reason I'd not bother to go to the hassle of getting a new paper gasket and either do as Max says** or just use a smear of RTV over the existing gasket as you mention.

I've done both on outboards over the past few years and they've not leaked.

**Max commenting on another thread the other month about making gaskets reminded me to replenish my stock of gasket material and I found a great selection pack of differing thickness sheets on Ebay for about £4.

You should be OK with a 2005 engine but make sure the two t.stat bolts feel right as you loosen and unscrew them as a small steel bolt in an alloy casting with salt water adj is a classic for breaking off or stripping threads.

[beerbelly]

thanks fenlander the dissimilar metal thing and the obvious salt crystals is another reason to have a look if the gasket is in one piece I think a clean and rtv should suffice and some copperslip on the threads of the 2 m6 bolts .give the stat a clean if that's gone furry too .never thought about it not being a pressurised system so thanks for reminding me

[The Gurnard]

Originally Posted by beerbelly

I am going to change the stat while its apart.its a 2005 mercury 15 2 stroke. many thanks

Hi Beerbelly,

I changed my thermostat last year. Like yours it was weeping at the housing and when I opened the cap..the thermostat and both its seals were disintigrating..along with the thermostat its self.

One was a rubber ring type washer that fits round the thermostat..the other just a gasket that you could cut if you wished. (The kit came with two cut gaskets..one a different shape from the other and I discarded the one that was not for my model)

I ordered the parts from Black Dog Marine.. and I got it next day

Here is the part that was for my engine..25hp Mariner.. it will be the same for the Mercury 15hp ?

Black Dog Marine. Outboard, Inboard Parts And Accessories