I've posted various questions before about rebuilding my mercury 850 serial no 7033755. I am currently at the crux of the rebuild, just before spending a great deal of money and would like some popular opinions about my options.<br /><br />The initial symptom was no compression in cylinder no. 2. I separated the power head and tore it down in my garage. I found out that one of the little tabs at the gap in the piston ring that keeps from spinning (i think it's called the index pin in the piston ring grouve) broke off while the engine was running and the ring broke apart. This left the top of the cylinder and the piston with bits of ring embedded in it. The cylinder wall was remarkably undamaged. I had all of the cylinder walls measured with an inside micrometer by a machinist and found out that the cylinders are very worn and he surmised that the ring broke from having to work so hard to keep up with the cylinder taper. My cylinders are tapered far out of spec.<br /><br />So the repair required is to have four blind cylinders bored at a cost of CAN$60 each which means four new pistons at CAN$150 each minimum. I'm looking at an CAN$840 repair min with a few hundred more thrown in for a water pump kit and gasket kit, and main seals. Probably about CAN$1200 all told.<br /><br />There are a few items that will derail the whole project. A new crankshaft is $1400. Project ender, period.<br /><br />One of the crank shaft journals (cly 3) has some wormy looking pitting. I can't feel it with my finger nail, but it's visible. It also has a spot which isn't shiny like the rest of it, roughly in the shape of a needle bearing. That dull spot again I can't feel with my finger nail. Is that what the manual descirbes as "water scroing" (more questions about that later)<br /><br />Additionally, the manual talks about "water scoring" in the section on inspection of connecting rods. My connecting rods have stains which look a little bit like oil on water does. The rest is shiny but in little "clouds" around a spot in the shape of one of the needle bearings, there's this discoloured area. It's not rough or pitted. But it's very close to the description that the manual says is "water scoring". The manual says, if water scoring is present the entire connecting rod set must be replaced.<br /><br />I could really use some information on what "water scoring" is, beyond the manual's description. It says "damage as a result of water contamination"<br /><br />I have some images that I can post, once I get them up on some web space.
