L/U oil change question

[whiskerwhipper]

I just changed the lower unit oil on my 9.9 hp 4 stroke Mercury on my own. I had to do it twice cause I wasnt fast enough with my fill plug that a substanial amount drained out before i could get in. So using my soap dispenser style pump i got from wally world, I pumped in more oil till it started spouting out of the fill hole. I was able to get the fill screw in before some oil (not all of it) drained out. How much oil seepage/loss is ok durin the fill stage? After doin the oil change, I notice on online instructions i was supposed to loosen the bottom screw before the fill screw when draining. I unscrewd the top screw first before the bottom screw. Did i do wrong? Is there a way i can check my oil level to see if i put enough in? many thanks

 

[Frank Acampora]

Re: L/U oil change question

If your engine only has two plugs--a top and a bottom-- then it doesn't matter which you loosen first to drain it. HOWEVER: With the engine vertical and both plugs out fill through the bottom until oil comes out the top hole. REPLaCE the top plug BEFORE removing the pump. Vacuum will hold most of the oil in but you still need to be relatively quick when you pull out the pump and replace the lower plug. Just snug the plugs so they don't drip oil.

Let the engine sit vertical for about 1/2 hour to let any air bubbles rise to the top. then, repeat the fill by removing the bottom plug and inserting the pump. Next remove the top plug and pump in the oil to top off.

Replace the plugs the way you did initially and tighten firmly so they don't leak.

Correctly done, you should not lose more than a few drop of oil. Any significant loss is unacceptable because the top bearing will starve.

 

[5150abf]

Re: L/U oil change question

Ya, after you fill it put the top one in first and it will keep it from draining out, as frank said, doing it this way you shouldn't lose but a couple drops.

 

[whiskerwhipper]

Re: L/U oil change question

thanks for the info guys. One more ? On the Tohatsu website, they say to check the gear lube level is to remove top fill screw. Then stick an inch long section of wire into motor and if it comes out with oil, you're ok. Would it work for a Merc too?

 

[Frank Acampora]

Re: L/U oil change question

Couldn't tell you. Ask over on the Merc forum.

 

[Leaky Lower Unit]

Re: L/U oil change question

Thanks for asking and Thanks for the answers! I would have tried to fill from the top if I had not come here and searched first!

 

[tustin77]

Re: L/U oil change question

im not saying this is correct but i fill from the top till it spills out. ive done it this way two years now and everything seems to be ok. but i make sure it is indeed full.

 

[Leaky Lower Unit]

Re: L/U oil change question

im not saying this is correct but i fill from the top till it spills out. ive done it this way two years now and everything seems to be ok. but i make sure it is indeed full.

Well I know what your thinking and it was the same as me but after reading the posts, I see that it is not at all like a car motor where the oil is free to splash around and there is normaly lots of air, but in fact it is a more closed tight system with passages and if the way they say to force it in with the top screw out is obviouly the way it was designed to be filled. This is why they make a pump for this purpose.

 

[444]

Re: L/U oil change question

Yes with a merc you always fill from the bottom until it comes out the top. Then screw in the top plug. Remove the pump and vacuum will hold 99.9% of the oil in until you screw in the bottom plug. If you ever want to check the oil you can pull the top plug and it should be totally full. You can also check the bottom plug to see if there's any water down there. Sticking a wire in through the top plug hole is a good way to check the consistancy of the oil for water contamination.