30hp 3cyl, cyl 2 dead

[TownsendsFJR1300]

In the old motorcycle 2 stroke world (and even 2 stroke, small yard engines), it's EXTREMELY rare for the crank shaft seal to fail.

Unless your talking about a 1975 Yamaha RD 350 twin 2 stroke, yes, seals start leaking with OLD AGE...

IME, a leaky crank seal (center) is pretty rare...

I would also think, if #2 crankshaft seal was leaking, it's going to "spill over" to either #1 or #3 or both. The air has to go somewhere....

[99yam40]

I agree, it should affect more than one cylinder if the seal between the crankcases was leaking.

how about the recirculation check valves being bad.
grasping at straws now

[walleyehunter13]

Is the recirculation #3 on here?
2001 30MSHZ Yamaha Outboard CYLINDER CRANKCASE Diagram and Parts

[99yam40]

Not sure on your motor, but if it is called a check valve I would make sure it checked.

My C40 had 3 of the 4 on it bad, I replaced all 4

[walleyehunter13]

Could it be an exhaust cover? I got white smoke but thought it was because of the misfire since my compression was fine and thought the plugs looked clean due to the gas washing them. I'll have to take the plugs out and get a good look at the cylinders and pistons and see if they look steamed.
This motor was barely used by the previous owner, but I'm pretty sure never flushed either since my thermostat area was almost caked with salt crystals.