Help with stopping corrosion in F150 thermostat housing

[Skiinver]

I have Yamaha F150 2005 engine's inside the thermostat housing there is some corrosion underneath where the thermostat sits

I am wanting to do some preventative work to stop it going through.
Has anybody tried painting with zinc primer epoxy two pack or galvanised paint to help the corrosion.

tried metal putty did not stick, glass fiber lasted 1 year.

I be grateful for anybody's feedback on what they have done to stop the corrosion.

The engines have had new anodes in each year and have been flushed out every time they have been used using the attached water connection and on muffs for short time as the engines over heat due to low water pressue in the yard.

Any ideas much appreciated. Alistair.

[fairdeal]

I bought my 2005 F225 in February 2014 with ~750 hours on it.

I pulled the thermostats for the first around November 2014
and discovered they were packed in wet "salt" - actually tore one apart in order to pry it out
(I had been flushing "religiously" - and the engine rain perfectly with normal temps)

In January 2015 I worked over the inside of the bores with Dremel stainless steel wire brushes and emery paper.

Washed the surface with alcohol, and painted the bore with zinc chromate primer (green aerosol)

Amazon.com: Moeller Green Zinc Chromate Primer Outboard Paint: Sports & Outdoors

I've been checking them every few months - most recently last weekend - and they look great.

Paint is still fully adhered and glossy almost 15 months, ~ 400 engine hours.

So a complete success as far as I am concerned.

I've read that in "exterior" use that zinc chromate needs a top coat -
but it clearly stands up fine "in the dark" - despite ~180 degree salt water.

I'm sure - as with any paint - "preparation" is 99%. I made sure I got down to "shiny metal" before I applied it.

I recall the aluminum corrosion was insidious - the "rotten" spots didn't look too bad, until I hit them with the wire brush. Then what appeared to be "metal" turned into "dust"

This photo would have been during the early stage of the cleanup.

[Skiinver]

Thanks

Many thanks for your feedback, I will have go cleaning them up and apply some zinc Chromate paint.


Many thanks

[99yam40]

When I cleaned up the corrosion on my C40 a hole developed to the block.
I had it welded up from the outside with a high frequency machine by a experienced welder and then used some marine JB weld on the inside so I could shape it to fit the stat back in properly.
He had a lot of problems with the welding due to the type of metal and probably the impurities