cylinder head corrosion - Mercury 75 hp 4 stroke

[old norton]

I have a 2000 Mercury outboard, 75 hp, 4 stroke, that is leaking oil because the cylinder head is corroded.
It has never seen salt water and has always been maintained religously. I was told that I will need to
replace the head at a cost of approx. $3800 just for the head. The repair shop said that Mercury only has
5 year corrosion warranty on this motor and that they don't have a program to address this issue. I have had
Mercury motors on my boats for years and have never seen this happen to any of them. In fact, I have a 40 year
old motor on another boat that is still running strong.
My question is: Has anyone here had, or heard of this problem before ?
If so what did they do to fix the problem and were they able to get any help from Mercury.

Thanks

 

[Texasmark]

Re: cylinder head corrosion - Mercury 75 hp 4 stroke

I am totally ignorant as I have never seen a 4 stroke engine, but will ask some "common sense...I think" questions.

On those old Mercs you mentioned, they were probably 2 stroke and had no removable head...it was integrally cast into the block. All you had was a water jacket cover and gasket.

I suppose the 4 stroke has a head. One can tell by observing the variations between the block and the outside of whatever is bolted to the block. If only a water jacket, there will only be one plate and one gasket. A head would constitute 2 plates, inner probably thicker due to it being an actual head, and 2 gaskets.

Then if you do have a leak, where is it leaking.....between the outer plate and seal, or inner and seal?

Are you mechanically inclined?

Do you have a service manual?

Point is, if you know how to (the manual) and can do the work (mechanically inclined), you can remove whatever is leaking, clean up the surfaces, put on a sealer (one made for the application...head gaskets or water gaskets) with new gaskets, torque to specs and tweak the valves.

Mark