Spi D
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How do you shaft drive types check your gear box oil level?..
Most often by a dipstick, just as for the engine.
Only drives with remote reservoir can be checked from inside the transom. Drives without needs to have a level-plug removed - and must be out of the water.
Finally, if my outdrive goes wrong I can buy an entire new one (which includes a gearbox) for more or less the same cost of a new gearbox for a shaft drive boat.
But still servicing over the years until you decide to replace, is very different.