I have a Beta 25 with the tmc40 transmission. Over the past summer, I have noticed a leak from the rear seal of the engine. It is only a drop or two when cruising at above 2000 rpm for several hours or more. I have monitored/adjusted the fluid level between the upper and lower dipstick marks (measured when the transmission is cold) with no change in the amount of leak after operationjust a few drops. When measuring the transmission fluid immediately after turning off the engine and the engine is warm, I am able to put my hand on the transmission case, the dipstick hole has positive pressure (good puff of air when removing the stick) and the reading is just over the top mark after wiping the stick and putting it in for the reading. The cold reading was below the top mark.

My Beta25 has approx 1600 hours mostly at 2200 to 2500 rpm continuous for 1 to 5 hours. Propshaft was checked during season and is still aligned.

Before I embark on a rear seal replacement, I am curious about of positive pressure in the transmission case and whether this is forcing fluid past the seal. The breather cap jiggles but how do I know the spring and "flapper" work? How much pressure should be allowed to build in the case? I can feel a good puff of air on my hand when pulling the stick while the engine is warm.