How othen does the trim pump oil need to be changed and what is the best way to do this? Thanks

I am not sure I would bother unless your boat is 10 years old. I have never actually seen dirty trim oil. Lets say it does 2 strokes per hour? Multiply that by your boat hours...pretty low wear item...atleast for fresh water.

The way I change mine is in 4 footers...the cap comes off automatically and you get to clean your bilge too

Unless you have water in the oil , I would'nt worry about it !

I used to change the oil in my tabs every 10 hours until I switched to synthetic. I now do it every 15 hours. I installed a cooler and that seems to help too. Or was that the drive?

Never changed it unless I had a problem with a pump.

Also if you want the tabs or drives to move faster, you can run a thinner oil. If one moves a little faster than the other, you can cheat by running thinner oil in the slow pump.