Mercury force cylinder rust damage… Usable?

[Beno]

Picked up this 90 horse 3 cylinder and the bottom cylinder got water in it and sat and it started rusting an obvious spot..

I hit it with a home and I spent a solid 40 or 50 seconds running the honer over the affected area.

You can feel the blemished area with your fingernail you don’t really catch your fingernail… but you can definitely feel the abrasion as your nail.goes over it ..

it’s not just cosmetic

The question is is it salvageable? Or will the block last 2hours then melt the piston and rings as the tiny part of the power combustion goes by the ring in that spot?

 

 

• This topic was modified 2 years, 11 months ago by Beno.

[billw]

It will definitely be down on compression. The engine will not perform to its full capability. But it will fire and run to a very limited degree. If you can still find an oversize piston, you should get it bored out now. You are in the perfect position to do it now. Why be disappointed later?

Long live American manufacturing!

• This reply was modified 2 years, 11 months ago by billw.

[Beno]

it’s really not that kind of situation.. . It’s a 90HP Force. So common.

for boring: you have to do a full tear down, then buy the new pistons, and new rings (and a stickler would even say rejet the carbs).

There’s no way the block is worth that money. It’s Sooooooo common and easy to buy a good 1990’s force 90 engine here.  (besides I don’t even want the 90hp. I’d rather have the 120hp 4cyl)

The decision is either part it out, or run it as is.  my only concern with running it as is, is getting stranded on the River. and a guarantee of ruining the $50 bottom piston and rings and connecting rod. all worth a little bit of coin online.  even the block itself at this point would bring some $..  someone who owns a machine shop could turn a profit.

perhaps I’ll try the compression numbers just to see where it plays out?

 

 

 

 

 

[billw]

Sure, try the compression. What the heck? Just don’t cheat and load it with oil…Just do the test as it stands now. But wouldn’t you have to put on a new head gasket to do that? $$$. “Boring” and “sleavng” are two entirely different things, by the way, with boring being way less money. I just had an 18 OMC cylinder bored for not much over $100. But yeah, the whole thing has to come apart.

Long live American manufacturing!

• This reply was modified 2 years, 11 months ago by billw.

[Beno]

I understand boring and sleeving somewhat.. it gets a little complex I think with sleeving you can pick your piston size because you’re inserting new material and having them either come as they are or made to your specification.

With resleeving I believe they shave out the old sleeve until it’s paper thin then peel it away like paper. Then press in new ones (and I was even told that they bore again after that because the sleeves comes a bit too small on purpose)  so I think you can choose (reuse) your piston size? (Or even return to the original size for your engine in case it’s been bored)

With boring I think you just increase the current steel hole diameter of the current steel by a  predetermined thousands of an inch.

Boring may be cheaper but I would still need to pay $200+ for boring all.3 holes. then 3 new oversize pistons, 6 new rings.

Easier to find an engine on the back of the boat that nobody wants at a garage sale.  Unbolt the head it and drop it in the jetboat

 

 

[Tubs]

I suspect you’ll have more compression loss from
taper in the cylinders (have you checked that) than
from the water stain.
Tubs.

A "Boathouse Repair" is one thats done without having tools or the skills to do it properly.

[fleetwin]

Well, you have little to lose, other than a bit of time and the cost of a head gasket.  Try it this way and see what happens.

[Author]

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