Tubs, I also have the Martin 75 "twist shift" which is a great running little motor.
Found out that it takes 40 Wt non-detergent motor oil in the lower unit.
I have all the Martin manual downloads from the JoeOutboard site, and have
printed off the pertinent pages to work on the Synco Twist, which I hope
runs equally well as it’s twist shift cousin when I’m done!
Tore some of the engine apart today to remove the upper and lower seals.
Learned that my poppet valves are not "lap-able" as they have o-rings on
them to do the sealing.
Anyone know if a standard o-ring works on those?
I haven’t searched for individual crank seals yet, but this is what I learned,
in case it helps someone in the future.
Top crank seal is marked "Garlock, part 175"
It’s OD is 1.250
Shaft size is .812
Thickness is .314
Bottom crank seal
OD 1.000
Shaft size .750
Thickness .131
The o-ring that goes in the lower bearing cap (along with the above seal)
appears to be the size of a R-12 in my o-ring kit.
This o-ring seals the driveshaft tube, keeping water out of the
lower crank seal.
My upper rod crankshaft journal is slightly / lightly scored.
Should I pull the crank and polish it some?
If so, what grit paper?
I don’t want to buy a new crank for this motor, so it either
gets polished, or left alone and hope for the best.
Too many outboards in the herd, so none get run that much anyway, lol.
Not sure if the rod bearing surfaces can be "refitted".
It has a tiny little aluminum rod cap….. can’t see how it "holds up".
.
