Mercruiser Alpha 1 Gen 2 out drive oil reservoir.

[lrg355]

I recently purchased a boat with a 2003 Mercruiser that has a gear oil reservoir in the doghouse. When I purchased it last fall I removed the out drive to check everything as I have done approx 50 times on previously owned Mercruisers and OMC Cobras in the last 40 years. Of course drained the oil and replaced it. No sign of water in the oil, looked like new. Also drained the reservoir. After reassembly, filled the oil from bottom to top vent screw as usual and filled the reservoir. Since using the boat it has pulled in a full reservoir and 1/4 of gear oil so far. Seems to drop about 1/8 inch per fishing trip. Probably pulled in about 10 or 12 ounces so far. No sign of oil anywhere on the water or elsewhere. I have not had any previous Mercruisers with the reservoir, so no experience with it. I am wondering if this is normal to fill any leftover spaces in the out drive up to the reservoir. Any comments before I pull the boat out and start looking for leaks would be appreciated.

 

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[mudflat]

How did you refill your reservoir when you changed the oil? 

The correct way is to pump oil in from the bottom until it comes out your top vent then put in the vent plug and keep pumping oil into the bottom to fill the oil reservoir and oil lines.  It is normal for the oil to "burp" itself  and the oil level in the reservoir to drop a little when you run the drive to get rid of any trapped air.  If you quit pumping oil when the level reached the vent and then refilled the reservoir from the top cap instead of the bottom you will have a lot more air to burp out.  At this point I would continue to watch the oil level and add as needed, it should level off soon.  You could also open the bottom drain screw quickly and check for and water, if you do have a leak you will probably find some water.

 

Hope this helps ; https://www.wikihow.com/Change-Your-Mercruiser-Gear-Lube

[lrg355]

Filled from bottom to vent hole, put in plugs, than filled reservoir from top. So my inexperience with the reservoir shows. Now I feel better and just wait till the air all bleeds out. Thank you for the info.

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[lrg355]

Going to have the boat on the trailer soon for Smart Tab installation and I had planned to check for water. Thanks again.

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[L&M]

On 6/28/2019 at 6:39 AM, lrg355 said:

I am wondering if this is normal to fill any leftover spaces in the out drive up to the reservoir. Any comments before I pull the boat out and start looking for leaks would be appreciated.

 

Provided you filled it in the conventional way from the bottom until it bled out the top vent, then went ahead & topped off the tank, you shouldn't have lost much more than a few ounces after the first run and any air had a chance to purge. 10 to 12oz indicates a leak somewhere & if your not seeing it externally, pull the drive again & see if there isn't oil in the u-joint bellows. If I had to guess your loosing it thu the upper yoke seal.   

[lrg355]

The link that Mudflat pointed to explains it all. I should have continued to pump in more after I put in the top vent screw until the reservoir started to fill. Then filled the rest of the reservoir after some was pumped in from below. Makes perfect sense. The 12 oz. pulled in is just filling the voids since I didn't pump past the vent screw.

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[mudflat]

If you're still using a fair amount of gear lube I would listen to Hank (L&M) and check it out to be safe.

 

Hank's old enough to have forgotten more than I know 

[lrg355]

Yes, going to pull it today to check.

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[lrg355]

As expected, Hank was right. This is what I found in the bellows and it is gear oil.

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