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Old 12 June 2006, 18:11   #1
Country: UK - Scotland
Town: Ardnamurchan
Make: Domar Corsair
Length: 4m +
Engine: Mercury 20HP
MMSI: What?
Join Date: Aug 2004
Posts: 215
Mr-d's stripping his engine!

Yes indeed.

I purchased an reverse lock cam on ebay for about 0.50 last year, thinking it was an easy job to replace.. but ooooh no! Definately not!

I have more or less stripped the whole engine and have found an awfull lot of crap in the water galleries, non original nuts, huuuge deposits from the exhaust, and screws/bolts/circlips that had not been undone in years.
Great fun, these 30 year old outboards

Anyway, just felt like showing what I had been up to. Its a shame I didn't take more pictures

Picture 1 - The bit I wanted to replace. The old one on the left, the new one on the right. Silly bit of plastic!

Picture 2 - Mercury clearly did not intend for this bit to be replaced very often. Look at how much had to come off to get to it! Lower unit, Powerhead, Driveshaft/exhaust housing, Shift shaft housing, clamp bracket. Oh what fun! It looks like a bombsite.

Picture 3 - There, finally the shift/drive shaft housing is off. The red circle shows the STUPID LITTLE @*$&@ plastic bracket that holds the reverse lock cam in place, ONLY accesible by stripping down the whole engine... the Yellow circles show recesses (sp?) into which rubber plugs sit to hold the shift/drive shaft housing to the exhaust housing. these were held in by circlips (hooray for salt water #1!) took about 1 hour each to get them out, knocking them back and forth and lots of WD40, my new found friend.
The powerhead nuts had been replaced with mild steel nuts, totally rusted and corroded, two of them had to be knocked off with a chisel.

Picture 4 - Take a look at the corrosion/deposits going on inside the water channel! The red arrow points to what once was/is the main water inlet hole (Straight from the pump at the bottom of the leg) I suspect that this would not be helping the cooling very much.

I then went on to remove the mounting plate from the leg itself, and cleaned it. I found a weird box type thing, which after scraping around in revealed some holes, and even screws, undid it and under 3MM of tar/oil deposits i found more holes, turns out to be a silencer or something, right at the top of the exhaust. Scraped away all the deposits, and cleaned all the tubes, stuck it back together. The actual gasket that was covering this bit was totally cracked and bloated, falling to bits.
After this I went onto the bottom of the powerhead, the whole head was covered in about 4MM of solid black sludge, its quite clean now compared to what it was, I should have taken some pictures. The water channel continues on the bottom of the powerhead, I found some more salt crystals, and bits of old rubber stuck in the main hole that runs up the side of the exhaust port cover, pulled them out, the main channel was totally gunked up with white deposits as well, scraped around cleaning it, and found another hole that appears to go straight around the side of the cylinder casing, which was totally blocked. Im sure that the gunk around the exhaust port must be acting as a insulation material heating the engine up more than it already would, plus the poor water circulation! The engine has been flushed at the end of each season (2 so far in our possession) and the tell tale was working fine last year.

Right, enough blabber from me, I am enjoying myself, my father thinks that I will never manage to get the thing back together again, but I am to prove him wrong (I hope)! All I need is some gaskets, or material to make my own, and some new stainless steel nuts to replace the steel ones. Perhaps some more WD40 and engine degreaser.

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Old 13 June 2006, 13:13   #2
Country: UK - Scotland
Town: Ardnamurchan
Make: Domar Corsair
Length: 4m +
Engine: Mercury 20HP
MMSI: What?
Join Date: Aug 2004
Posts: 215
Some more pics

Picture 5 - Exhaust cover removed. You can clearly see the water channels on the bottom left corner, top and right hand side. Full of GUNK! (and some quite cool looking salt crystals!) More of the black stuff, about 1MM thick throughout. I am almost starting to wonder what good the Powertune stuff actually did, it probably removed a bit of that oil and that's it!

Picture 6 - Same as above, but cleaned (And yes, I did position the flywheel so both cylinders were closed before starting to clean.) Its amazing what WD40, a cloth and various implements with edges can do! The water should be able to get around the block without any problems now, and the oily substance shouldn't be insulating the cylinders any longer.

Picture 7 - This is the outside plate of the exhaust cover. The gasket is still in place... this plate assembly is quite important, it runs the cooling water around inside it, as you can see its very nice and clean (not!)

There, some more boring stuff Oh, and I phoned for the gaskets today, but the guy hasn't got in touch yet (which he said he would today.) So I might just make them myself.
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Old 13 June 2006, 13:35   #3
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Country: UK - England
Town: The wilds of Wiltshire
Boat name: WhiteNoise/Dominator
Make: Ballistic 7.8/SR5.4
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Join Date: Jul 2005
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Looks like you got quite lucky with that engine-most 30 year old engines that have been in salt water don't come apart without breaking every bolt going.
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