TOPIC: 850 FGS

unless someone can answer faster than me I will take photos of the NOS block I have for this motor. Judging from your pictures nothing is jumping out at me. Were any of the weights on the crank bent? was there a tossed bearing anywhere? your piston trouble would be inside the cylinder sleeve not in the area you pointed out. Was anything else in the motor splattered? What you point out could just be imperfections from when the block was cast.
I will take some pics and try to post them soon so we can compare a NOS Block with a block that has seen service.

Jim

OK here are the photos of my NOS block and crank. It is actually a 800 FGS but it should still offer you something to compare to. I still do not think you have a problem with your block. Low compression was most likely stuck or partially stuck rings.

Jim,

Thanks for taking time to post pics of your NOS block, I hope the 850 block looks that clean some day. After inspection the top rings on the #3 and #6 pistons were stuck. Being this is my first rebuild I wanted to make sure that what I was seeing was not a problem. At this point I think that ut may be due to the casting of the block.

I have not had a chance to get back out to the shop due to work and family. My brother is a new father as of yesterday, new uncle Curtis!

CD

Yes thanks Jim, now I know what my 800FGS is suppose to look like inside! Hopefully it will if I can aver get back to it!

Bob

Bob,

Your post on your 800FGS was one of the things that gave me encouragement to "go for it".

CD

CD, always here to help. If I can just get the "honey do" cupboards done I can get back to it. keep up the good work on yours.

Bob

Uncle Curtis,

Congratulations!

Okay - back to Mercurys,...I'm a bit concerned with the condition of the journals on your crankshaft.
I suppose it could just be stains, but if you can feel any of what appears to be needle bearing etchings in those crankshaft journals, and they won't polish out with emery cloth - you will probably find similar conditions on the rod caps and wrist pins.
If you do - you might want to be on the hunt for a replacement crankshaft & rods with good wrist pins.

Professor - what is your opinion??
Dave - ???

Curtis,
If that ends up being the case I might have a good crank and rods. I plan to open up a couple of 90ci TIGER powerheads within the next couple weeks and if I find more than what is needed to build one for myself the rest will be up for grabs at a reasonable rate.
I might also have a crank or two in my too good to toss pile for the TIGER series, but I would have to see if they a A-1 or not. (sometimes when I tear down a motor and I'm not focused on the crankshaft - I set them in the corner until I need to carefully inspect them before use or sale.
Thom

Probably the other Dave you are asking, but this Dave agrees with your concern over the Staining on the journals. It is clear that the needles have rusted in place, leaving the stains or possibly pitting as well. Crocus cloth is the recommended for polishing the crank journals as emery cloth will leave embedded mineral in the journal. Crocus cloth is getting harder to find if at all. An alternative is an aluminum oxide cloth abrasive. It will tear lengthways to the correct width for the journal for you.

Thom, Dave,

Thank you for the advise on the crank journals. Yes there is some staning on several of the journals, rod caps and wrist pins, but I do not feel any roughness with my finger with the exception of the reed block journals. I was hoping the staining could be polished out as suggested.

I am still working on cleaning all the gunk and carbon off of the block, the stuff is a bear to remove. I hope to have it cleaned up this week and will post better pics of the cylinders when I am done.

CD

Colour stains can be polished out.---Rust pitting is another matter.

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Water works its way into the material ( all material is porous to some degree ) and weakens the structure of the metal.-So it must be absolutely free of pitting to be a long lasting motor.

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I always use narrow paper and polish to get a " cross hatch pattern " on the journals.

Not saying this is the case, but maybe something to consider, I have a block opened up from a motor that runs well and it too has the very similar rust stains, this motor was submerged a year ago, I flushed the water out and fired it up for the guy, its still runs a year later and now is in for rings and bearings so I got to see the water coloration from its dunking last year
so if you dont know the history of the block...maybe

professor wrote:

Colour stains can be polished out.---Rust pitting is another matter.

---

Water works its way into the material ( all material is porous to some degree ) and weakens the structure of the metal.-So it must be absolutely free of pitting to be a long lasting motor.

---

I always use narrow paper and polish to get a " cross hatch pattern " on the journals.

Agreed, the stain will polish out, the pits will not. A quick way to polish the journal or the throw is to cut a strip of 400 grit aluminum oxide paper into a strip that just wraps around the area to be polished and overlaps itself by 1/4 inch. Tape it together with masking tape. Now take a shoelace and wrap it 1 1/2 times around the abrasive and pull the string back and forth, one hand pulls one way the other pulls back. As you work the lace back and forth you can cover the whole area. With this method I cut the abrasive undersize to the journal so that it does not catch and jam. You will be applying equal pressure to the full circumference and will quickly polish the surface without missing anywhere. Cutting oil aids the process but eventually softens the tape.

Mad,

The only history I know on this motor is that it sat in a storage lot in Eastern Colorado until the owner of the lot sold out and the new owner sold the boat w/ motor attached. The boat w/motor was last registered in 05. I went to the local yearly boat show and I had one merc shop tell me to scrap the motor and buy something from the early 80's. The other shop was so timid about giving me any advise that I decided to take on the project as a learning experience more than anything.

Dave, Professor,

Thank you for the advise on polishing. I have heard similar instruction on other forums.

Attached is another picture of th crank showing the wear from the reed blocks.

CD

LandSurveyor wrote:Dave, Professor,

Thank you for the advise on polishing. I have heard similar instruction on other forums.

Attached is another picture of th crank showing the wear from the reed blocks.

CD [/quote]

Have a look at the reed block ridges, if they are mushroomed over you will have to find replacements. In theory, the blocks should never touch the crank, there should be a film of oil that acts as a seal between the cyls and as a barrier to wear. In practice, what you see on the crankshaft is pretty typical, especially if the end bearings are getting tired or have water intrusion. One of your end caps showed the bearing with rust on it. Polish the crank and see how it cleans up. There may be some hills and valleys where the reed blocks have contacted the crank. You will not be able to remove those and it will be a judgement call whether or not you can get away with it or whether the new reed blocks will take up the gap.
Other opinions may vary.
Hope this helps