Oil change question

[Whitehorse]

When changing the lower unit lube, the instructions I saw said to fill from the bottom hole until the lube comes out of the top hole. (I have a 2001 Merc 2 stroke). With the pump and tubing I have, it's kind of a pain to get the lube in without it going everywhere, since the tubing and hole don't line up well. And when full, closing up the top hole is supposed to help hold in the lube while you put the bottom screw in, but it still drips out pretty good.

My question is, is there any reason why filling from the top wouldn't work the same? It seems to me that it all goes into the same area, so why not fill from the top?

Just trying to avoid some of the mess and hassle from last year (my first time ever doing it). Thanks!

[kryptonite]

You can get air trapped in the gearbox if you fill from the top.

It's just typical you get a little that runs out before you put the plug back in. Just part of it.

[babock]

If you are not using something that threads into the bottom hole, you should buy something like this:

https://jet.com/product/product/eaffc03 ... oCnWfw_wcB

You want to fill from the bottom hole only. As mentioned by the previous poster, you will get an air bubble that makes it look like your unit is full when it isn't. It's what the manual specifies.

[BoatCop]

The kit for filling the lower unit from the bottom should have a threaded connection so it's a positive seal. The pump kind so you can use bottles works better than the squeeze tubes, that spill oil all over. It may cost a few bucks more, but if you routinely change your own oil, it's definitely worth it.

Make sure that you're replacing the gasket/ O-ring on the plugs every time you change the oil. If the oil flows out the bottom, rather than a slight drip after you put the top plug in means there's an air leak breaking the vacuum that should hold the oil in. If air can get in so can water. I'd have the lower unit pressure tested for leaks.

[Bamaman]

When you use the threaded tube on the bottom hole, you can usually get by with 1 quart of lube. If the top vent plug is tight, hardly a few drops of oil comes out the bottom hole.

I still have a hard time hearing of those paying dealerships big money to change oil and lower unit grease when it's a simple 25 minute job and $35 in supplies.