lower units

[stormmn]

so glad you guys all made up!

now for my question, why does the "book" say to fill lower units from the bottom plug?
(I have asked a couple marine mchs. this question and they just say, "the book say's so".

So like I fill my engine (4 stroke) from the drain plug, my trucks rear axle from the (never mind, I can only fill from the top plug) see my point.

why fill from the bottom plug rather than the top plug????

thanks, look forward to the answer...

 

[merc850]

Re: lower units

If you filled it from the top with the lower plug in, air will just block the flow. Even if you loosen the lower plug to let it seep out you still can't get a complete fill with no air pockets, I'll bet your truck's oil fill hole is about one inch dia. with plenty of room for air to escape.

 

[rjedney]

Re: lower units

right answer on lower unit filling with oil.

 

[Dave1027]

Re: lower units

I'll bet your truck's oil fill hole is about one inch dia. with plenty of room for air to escape.

and no narrow passages to trap air like a LU has.