Engine corrosion

rothwell_neil 5:56pm, 20 December 2007
I will be posting pictures of the corrosion on my Honda. You can see that all looks well until taken apart, the leak from the head wasn't too bad except on full throttle. This was due to the fact that most of the passages were blocked thus water couldn't get out of the hole!
Skykomish E29 11 years ago
So Neil do you use any chemical to get rid of the salt build up?
rothwell_neil 11 years ago
The only prescribed way of getting rid of corrosion product chemically without damaging the substrate is phosphoric acid with chromium trioxide. As this is not possible in the domestic world then chiseling it out with a screw driver and then polishing back to bare metal with brass brush on a dremel is the best way. Air helps re-passivate and boiling water does it quicker. The problem really is when scales start to build up as clean aluminium in seawater is OK unless connected to anything steel.

12 years is too long between fixes, the evinrude was 30 years old and whilst clogged up was in good nick. Cast iron seagulls are bomb proof!
Skykomish E29 11 years ago
Thanks was hoping there would be something to pump through the outboard as part of an annual service, as it is not practical during the summer months to flush with fresh water after every use like we did on the dive boat.
Unfortunately bomb proof they maybe but Seagulls aren't too enviromentally friendly with their 25:1 fuel mix .
I believe they are not renowned for their reliability either.
rothwell_neil 11 years ago
Seagulls are synonymous with reliability! We dropped one off the back of our boat when i was kid, all my dads fault obviously, waited for the tide to go out, pulled it out of the mud, drained tank and carb, took out plug pulled it over a few times. Refilled and off it went again. Nothing to go wrong with them ever as they are agricultural. I got one off ebay as a nostalgia trip and whilst it came siezed and very sorry it runs a treat. 25:1 is only if you re-jet them otherwise they run on 16:1 which must make them close to diesels.

I can't think what to do with a motor in the well as difficult to wash through. I guess I would keep an eye on the outlet water and if not at full flow consider a clean. Two strokes can be done in a matter of an hour, 4 strokes a bit longer.
busy home [deleted] 11 years ago
I was told to use vinigar what do you think?
Skykomish E29 11 years ago
mmmmmmmmm presumably an hour or so to clean an outboard must mean dismantling it to some extent, so I would think in the hands of an amateur that would extend to several hours.
I know that I had all sorts of problems when I dismantled an old Evinrude 25 h.p. to repair a leaking gearbox. The reair was straight forward but reassembly caused problems as I couldn't re locate the tube that fed the cooling water to the power head, even took it to a "so called" outboard specialist for repair and he had problems and it turned out that he botched the repair with silicone!!
So I am a bit reluctant to get too adveturous with my nice shiney 3 year old litle used Mercury.
Perhaps you could post some step by step pictures of what is involved with a descale I am sure others would find it useful
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