Suzuki PU40 - 1992 - Oil leaks from exhaust when boat is in storage

[MO Boats]

My 1992 Suzuki PU40 (jet) started leaking oil out of the exhaust tube and exhaust vent when in storage. I replaced the check valves (2) on the oil injection lines, which slowed the problem but did not fully keep oil from leaking at exhaust when in storage. Motor has a hard start when cold, with lots of smoke on start up, which I suspect is due to oil migrating to one or both cylinders during storage. Once the motor is warm, starts easily with no smoke.
What keeps oil from migrating from the oil reservoir through the oil pump and check valves, during storage? Is there a way to test or rebuild the oil pump, as I am unable to find a new OEM oil pump. I am reluctant to put on a used oil pump, as my current pump work fine when running.

Thanks for your consideration.

Missouri River Runner

 

[99yam40]

you storing in laying down or up right?

 

[MO Boats]

you storing in laying down or up right?

Storing upright on transom of boat. The amount of oil leaking has slowed and I suspect there is residual oil trapped between the midsection and adaptor plate for the jet unit. I will remove the jet, clean the midsection and see if that corrects the problem. Thank for your reply.