Mercury 4cyl needle bearings shrapnel failure

[Beno]

I seem to be in possession of a four-cylinder Mercury that the needle bearings have found their way into the cylinders.  See attached pics.

Anyone have any advice with the best way to get the Piston out it’s completely wedged. You can see the needle bearings as they’ve got themselves in between the piston and the Piston wall.   They must have snuck in through the intake.

After anyone guesstimate the amount of boring that will take to get those scratches out of the Piston walls 30 over, 60 ove

r 90 over?

[billw]

Is that a Mercury or a Force? I can’t think of any Mercs that had a head gasket except V6s. Is it a Mercury Sport Jet 120? They used four cylinder Force power heads.

Without knowing what engine it is, I couldn’t know for sure what available OS pistons you could get; but those grooves in the cylinder wall are VERY deep. I seriously doubt that one is worth saving.

Long live American manufacturing!

• This reply was modified 2 years, 8 months ago by billw.

[dave-bernard]

short of resleaving that block, it is junk

[Bob Wight]

Yep, that’s a boat anchor unless you can resleeve the block.

Bob

1937 Champion D2C Deluxe Lite Twin
1954 Johnson CD-11
1955 Johnson QD-16
1957 Evinrude Fastwin 18
1958 Johnson QD-19
1958 Johnson FD-12
1959 Johnson QD-20

“Every 20 minute job is only a broken bolt away from a 3-day project.”
"Every time you remove a broken or seized bolt an angel gets his wings."

[Beno]

Yes it’s a mercury force. . in this area of the country Mercury forces are on every street corner. They are by far the most popular engine around. Not sure why.

I figure the engine’s a total loss but there’s a possibility that it could be overbored. The 120hp is in demand. Could also just pull that piston and go with 3cyls.

Another one bites the dust

 

 

[need2fish]

I’ve overbored my Force 90 and 150 — it’s simple enough, but I stopped at 30 mil over. It makes a heckuva difference on torque and mid-range acceleration. Not sure if there are pistons available for higher than 40

From what I can see, Force 3-4-5 powerheads have a bad habit of eating the rings on the inner cylinders. This is due to oil shortage which is caused by fuel shortage (which is caused by the middle carb(s) starving.

Which leads to the conjecture of there being many failed force powerheads out there that require overboring (instead of yours which may also require rods and crankshaft repair) — maybe you can find one and bring it back to life.

[Beno]

I’m not going near it. I’ll just part it out.  I havn’t opened up the intake/crank Chambers yet but I’m fairly sure there’s going to be some damage there too from those needle bearings.  Things are pretty tight tolerance and needle-bearing it’s got to be at least 1/8 of an inch.

Furthermore the crankshaft can’t possibly be in very good shape after those needle bearings squeak their way out?

• This reply was modified 2 years, 8 months ago by Beno.

[billw]

Yeah, Force 3,4 and 5 cylinder engines did eat rings all the time. I don’t recall that it was always one particular cylinder, though….That was around the time that OMC cross flow V engines were eating them, too. Their top rings had a “pressure back” or triangular design. What ever the reason that they let go, If you had an OMC piston on one side of the room and a Force piston on the other side of the room, you couldn’t tell the difference. It was like they came from the same vendor or something. (I’m talking about regular OMC pressure back rings, here, NOT the OMC high ring pistons, which were even worse.) If the power head in question is from a conventional outboard, I would junk it. If it’s in a Sport Jet, those are pretty unique and I would try to save it with another power head.

Long live American manufacturing!

[Beno]

ok I have the block all broken down… on the three good pistons I pulled out.. I was noticing that the lower part of the connecting rod is “match ground” making each unique to it’s counterpart.  is this normal?

secondly can you re-use the connecting rod bolts? (1/4 heads 12point/12spline), and does anyone know the torque you would set them to?

thankx

 

 

 

[billw]

Yes that’s normal. Any modern connecting rod that I am aware is machined as a matched assembly. You can reuse the bolts. I will look up the torque but I am curious as to why you want that information at this point? You’re not going to try to put it back together with one piston missing, are you? It won’t end well.That would be a total waste of time.

Long live American manufacturing!

[Author]

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