thanks Craig, that makes more sense. I'm gunna watch piston wash to jet it.. glad to hear I may be starting rich.

C vs. D vs. no letter: they all look the same from the outside in terms of their outer diameter and threads. The C vs D looks like maybe the actual jet I.D. bore might be different lengths on the inside: So looking at the part, it starts as a larger bore, then down to jet size for a small length, then back up to a larger bore.. Hard to tell as the 59C jets I have are dirty and a bit damaged.

Also, I have a set of 60 jets (no letter) that look like a 0.060 just at the rear of the jet for a short length. Larger bore for the rest of the length. These are factory jets for a 1969 55hp 3cyl OMC.

Difference is the direction of fuel flow through them, the D flows front to back, the C back to front

I don't think that is true.

59C is factory stock on the 1973 3cyl 65hp. That's where the ones I've seen have come from.

So what would make an SST 60 wear out so fast?
The high revs?
The high compression?
Or the improper unbalance rotating mass?

Here you go Mike.
First off EVERY SST60 motor that raced in Ontario and went racing in APR Superleaque ....failed inspection.
Jeff Titus let them race because the were tail enders, but warned them he would DQ them should they finish top 3. He told them to get legal motors. The top Canadian racers did get legal motors and found the legal ones were BETTER than the illegal ones. So if? you happen to have one of the illegal ones chances are it has a short life span.
The thing that hurt the motor the most was the LeMans start! To get punch off the dock we had approximately 3 thou piston clearance. You loaded the motor with fuel and used 24 volt starting. Those first few seconds of running put way over 220 compression in the motor and that was hard on the motor.
When the race course was longer [45 seconds or more] we ran 7700 to 7800 rpm. Once they shortened the course [35 seconds] we ran 8100 to 8400 with lower pitch props and some of us ran the motor much higher so it only got a drink of water in the turns.
The SST60 is very happy running mid 7000's, over 8000 is hard on them.
I tell people with SST60 motors to crank them first and then use the primer. That way you don't hurt the motor starting it.
I had two 30 over motors that I couldn't legally re sleeve due to deck height. I used 40 over aftermarket square ring pistons and a 160 compression head. GREAT LAKE motors and they LAST!

YES MATT, I WOULD MOVE THE WATER DUMP TO THE TOP OF THE BLOCK ON THE 49.
http://www.mccauleyandson.com/images/1975evinrude3.jpg