Best way to fill oil in an installed Top loader ?

The above is a good warning if you seal the filler tube to whatever you are filling. As long as you only stick the fill tube from the pump into the filler hole, without being sealed, you will be fine. Excess oil will run back out from the filler hole once it is full.

Note, for the actual application of the marine pump I linked, the fill procedure is to connect the filler hose sealed to the drain hole of the lower unit of the outboard motor. The fluid then fills up the lower unit until it seeps out the filler hole. This ensures the lower unit is actually full without being fooled by air bubbles that may occur if you were filling from the upper fill hole.

Great Ideal, Thanks

Rufus68 said:

Note, for the actual application of the marine pump I linked, the fill procedure is to connect the filler hose sealed to the drain hole of the lower unit of the outboard motor. The fluid then fills up the lower unit until it seeps out the filler hole. This ensures the lower unit is actually full without being fooled by air bubbles that may occur if you were filling from the upper fill hole.

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So how then would one remove the fill tube and replace the drain plug without gear oil spilling out all over the place? Or am I misreading what you are saying here?

patrickstapler said:

So how then would one remove the fill tube and replace the drain plug without gear oil spilling out all over the place? Or am I misreading what you are saying here?

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You read it correctly. I've done it many seasons. Once the gear oil starts running out of the upper filler hole, you put the filler plug back in first. Then when you remove the pump hose fitting from the drain hole, the gear oil barely begins seeping out which gives you the time you need to put in the drain plug. Vacuum pressure created by the sealed insides of the lower unit is holding the oil in. The system works really well. The fitting on the pump is made to thread into the drain opening on the lower unit of an outboard motor. Remember the hole size of the drain isn't very large.