Refilling Mercruiser Lower Unit

[dandi]

We recently replaced the lower unit on our Mercruiser stern drive. We are in the process of refilling it with gear lub. When pumping the lub in, it became difficult to pump, but lub never came out the top vent hole, instead it started oozing out the opposite side from a small hole. Everything thing I have read indicates it should be filled until it runs from the top.

Any ideas? Is this normal?

 

[Bt Doctur]

Re: Refilling Mercruiser Lower Unit

We recently replaced the lower unit on our Mercruiser stern drive. We are in the process of refilling it with gear lub. When pumping the lub in, it became difficult to pump, but lub never came out the top vent hole, instead it started oozing out the opposite side from a small hole. Everything thing I have read indicates it should be filled until it runs from the top.

Any ideas? Is this normal?

oozing from the opposite side? Of what and what hole.
Yes, you filll from the bottom untill it comes out the top.

 

[dandi]

Re: Refilling Mercruiser Lower Unit

There is a small hole on the side opposite the fill hole and the gear lub is coming out this hole. We have put a quart and a half in and it has not shown any indication it is full and it has become very hard to pump, like there is an obstruction or no place for the oil to go.

 

[dandi]

Re: Refilling Mercruiser Lower Unit

Apparently this hole that we have lub coming out is the weep hole. I notice the links at the bottom of the page with some pics posted in one.

I can see that the lower unit is going to have to come off for inspection to see what the problem is. Is it possible to take the lower unit off while leaving the upper unit attached to the boat or is it just easier to take the whole stern drive off and separate them on the bench? We are so close to finishing up a several month restoration project, would like to know the easiest way at this point.

 

[ziggy]

Re: Refilling Mercruiser Lower Unit

would like to know the easiest way

it's easiest to put the two halfs together on the bench, i think others will confirm this.
i've had the lower only off quite a few times on my boats. it always greeves me puting it back. a two man job for sure, and if it don't go, yer back will know it after many trys. it can be done this way though......
i pulled the whole drive the last time for other service, putting it back together again, the lower and upper, is a one man job on the bench and went very smoothly, no back pain, no new swear words.... + ya get to check everything else out if ya pull the whole drive.....

yer right, when ya fill it with lub, ya fill from the bottom hole (drian) till it comes out the top hole (vent). if ya can't fill till it comes out the vent, somethings up, ya should not feel resistance when filling with lub + there should not be oil comeing out the hole on the other side of the lower, water comes out that hole....

 

[Don S]

Re: Refilling Mercruiser Lower Unit

Was the oil hole where the quad ring goes for the oil passage open? It may have been taped over to keep dirt out. There is also a seal leaking somewhere allowing gear lube to get to the water passages. Did you really pressurize the oil while trying to force it in?

 

[dandi]

Re: Refilling Mercruiser Lower Unit

I thought that taking the whole unit off and splitting the two would best be done from the bench. Past experience has shown us that this is the easiest but thought maybe we had done something wrong.

We only used a hand pump on a bottle of gear lub. He did apply some pressure but not sure how much. The game plan is to pull the stern drive separate the upper and lower and inspect all the items mentioned in another link. We will check for tape. Instructions that came with the new unit did not mention it among all the things to look for and do but it could still be there.

Thanks for all the assistance. This big boat is new territory for us.

 

[dandi]

Re: Refilling Mercruiser Lower Unit

Got the upper and lower unit apart and sitting on the work table. It appears the little gasket on the oil tube has slipped and was not in the correct positon.

Slightly concerned that the spot on the upper that this mates too is not smooth enough for a good seal. There is a little nick in the tube at the very top. Can this be patched? Or are we looking at a new upper also? Looking for some guidance on this one.