Chrysler 55hp rings

[rapier]

My Chrysler blew a head gasket and cooked a piston a year ago. Looking through spares I inherited I have 4 or 5 NOS piston ring kits with part number S310260 – I believe they fit .010 oversize pistons for the 45hp (marked SA435015), I think these oversize 45hp pistons are the same dimms as the 55hp standard piston. Does anyone here know whether the standard 55 rings (A311260) are interchangeable with the 45hp oversize rings (S310260)?

• This topic was modified 5 years ago by rapier.

[garry-in-michigan]

I don’t think so – the bore of the 45 horse Chrysler is 3.1250″, ten over would be 3.1350″. The 55 horse has a bore of 3.1875″. I believe you would be pushing it to trim the 55 horse rings to fit your 45, but I am not saying it can’t be done . . . Piston ring end gap should be 6 to 16 thousandths (0.0930″ + or – ) for thermostat equipped outboards. Engine compression for your 45 should be 115 to 130 PSI. Gearcase capacity is 12 ounces. Good Luck –

[rapier]

Thanks Garry, much appreciated. I ran the same calcs – was thinking of using the 45 rings on the 55 (1967) that got cooked. Just wondered if there was someone very familiar with these part numbers here who’d come up with an answer that might save me $60 in cost & tax for the 6 new rings. My current Mercury EPC only covers the ’74 Chryslers onwards, nothing prior to that.

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