Reply To: MERCURY MARK 55 PISTONS

[jeff-register]

Lab guy,

I used to get seals by size from State Seal.com here in Phoenix Az fpr my Firestone (Scott Atwater) motors.  The problem with the Mercury seal is it’s threaded into the lower unit. the threads for a mk 25 & a KH7 are the same but the threaded hex collar that is molded ino the seal (brass) the hex head to tighten to the lower unit is wider on the mk 25 & will not fit into the KH7 leg without grinding material from the KH7 leg. Mercury must of made the seal collor hex bigger as a upgrade. The threaded seal swaps either way except the KH7 ; is thinner in the lower leg. Also The KH7 had overheating problems & Mercury had a revision waterpump assembly’s to correct this free of charge. I’m not sure if my motor made it back for this revision. The Mark 25 had a much better waterpump & stronger bearings, shafts & gears. All I need is a new KH7 shift shaft seal to complete the upgrade. I’ve tried Joe Pool too, My KH7 is such low hours the pull rope is still white with the red line on the rope. It sat in a dealership on display for many years before I bought. Yes I gave too much $1000.00 for it but it’s like brand new & don’t want to grind the leg. P.S. I couldn’t afford this motor now I’m retired.

Thanks for the  input,

Jeff