Hi, I need to change my bow thruster oil. When this was last done they pumped the oil up from the bottom. Is this really necessary? Would it be possible to simply drain the oil, then fill from the top until the new oil starts to drain from the bottom before closing the outlet? Thanks Paul Amel 54 Ya Fohi
Thanks for all the replies - I didn't expect this would generate so much interest!
I do have a drain plug at the bottom. This is just routine maintenance - the unit is working perfectly. I just wanted to know if it was really necessary to pump the new oil in from the bottom as the last time this was done the boatyard insisted that is was necessary to avoid getting trapped air in it. I don't have any equipment to do this. I'm convinced however that as long as I keep the drain open when refilling from the top there should be no trapped air and I can close the drain as soon as the new oil starts to come out. This is my theory anyway! Paul
It sounds like filling from the top would work although the yard guys may have a point about filling from the bottom drain hole like an outboard lower unit to avoid air pockets. Any chandlery will have a very inexpensive manual pump they sell with the gear oil, if that would fit.
