Lower unit oil WILL NOT go in.

[oilxplrr]

I have a 1978+- Mercury 20 HP outboard motor. I know this is the simplest boat maintainence thing there is, and I've done it many times on other motors, but...I am unable to inject oil into my lower unit. Yes, I HAVE removed the top vent screw, and I'm injecting into the bottom hole. It's like I'm trying to inject oil into a brick wall. I pulled the lower unit yesterday (no small task) which was a waste of (all afternoon) time, and of course I couldn't see a thing, so I put it all back together. <br /><br />I've gone as far as connect a tube of oil to the lower unit and stood on it to pressure it up, but cannot get any oil in there. Then I tried squeezing the tube of oil between two boards with a pair of clamps, still nothing... and we are talking fairly high pressure. I can hear an occasional squirt of air through the vent, but I made no progress in a couple of hours of stomping, squeezing, and cussing.<br /><br />What am I missing? Could the lower unit be completly clogged up? I looked into both holes and could not see anything weird inside...probed around the bottom hole with a screwdriver, but felt nothing in there. The oil that drained from it looked OK, no water or gunk. Of course, now I've managed to drain it completly dry, so I've got an unuseable motor.<br /><br />Anybody got any suggestions? Thanks

 

[alcan]

Re: Lower unit oil WILL NOT go in.

Hi Oil<br />If oil drained out of your lower unit then it will go back in. Sounds to me like you need to fully open your oil tube. With all that stomping and squeezing you should have oil all over the shop.

 

[BF]

Re: Lower unit oil WILL NOT go in.

Hiya,<br /><br />Are you SURE that you removed the vent plug (and not some other screw)? Sure sounds like what would happen if you only removed the drain plug. It would drain, but slowly and be impossible to fill.<br /><br />I know I'm not much help... but it's the only thought I had. PS, have you changed the gear oil before on this motor? <br /><br />Also, you are filling from the bottom, with the vent plug out - right?? <br /><br />You would have this problem if you put the drain plug in, and then tried to fill from the vent hole (that's the wrong way to do it). The point of having the vent plug off is to have a place for the air to escape as you fill with oil from the drain plug (bottom).<br /><br />Hope this helps.<br /><br />Brent

 

[slow_boat]

Re: Lower unit oil WILL NOT go in.

Try putting oil into the 'vent' hole & see if it comes out the 'drain' hole you opened. Don't know if these mercs have a screw adjacent to the drain hole as do some of the older johnnyrudes but if they do you may have removed the shifter fork screw instead of the drain?

 

[oilxplrr]

Re: Lower unit oil WILL NOT go in.

OK, so now I'm embarrased beyond recognition. The upper screw I was removing was a flush plug, with the upper drain screw sitting below it. My other motor's upper plug looked exactly like the flush plug on this one. BF, your question about being sure I had removed the right screw made me go look again. The vent screw was a booger to get loose, but I got it, and filled 'er up with no problem. Just checked it out, and I'm pumping water and shifting in spite of my unneccesary lower unit r&r yesterday, at least now I'm a veteran of that activity. I'm all greased up and ready to go fishing! Thanks a million for the quick responses, you guys.

 

[BF]

Re: Lower unit oil WILL NOT go in.

Embarassed or not, it's good to figure it out without more time or $$! Glad I made you go look again. See, selective use of caps DOES help!<br /><br />Good luck fishin'<br /><br />Brent