I doubt its the valve and its doing it job. The likely culprit is the pressure fitting on engine block that supplys air pressure to boat oil tank. It has a small hole that bleeds pressure off when engine is at rest. if oil tank overpressures the check valve will open and the result is what you...
Gear ratio is different between a V6 and V4 looper but can share the same big diameter gearcase. Put the port motor in gear and rotate the flywheel 1 full turn and count the rotations of prop.
Test it in a barrel to see if alarm goes off. If oil system was not properly done it could be low oil alarm on engine oil tank. You cannot just unplug the oil pump on boat side tank to bypass.
