Lower Unit Pressre Test

pk · #1 10-20-2004, 08:15 PM

;D

Hello; I would like to know the proper procedure for doing a pressure test on my outdrive. Specifically, I have a 1988 V-20 with a 205 mercruiser. The lower unit has a remote oil resovoir on the transom. Every year I lose about an inch of oil ( about half a cup or so) from the bottle. I never see it in the water & there are no leaks in the boat. I suspect I may have a seal leaking somewhere & will try a pressure test to try to narrow the problem. Thanks in advance for any feedback.

#2 10-21-2004, 12:49 AM

Is this really a problem?

I dunno about i/o's, but pressure tests can cause problems, so if it ain't broke - don't fix it.

chumbucket · #3 10-21-2004, 02:15 AM

I agree with Seakindly. If not done properly, pressure tests will definately cause problems. Do you get water in the oil? It would show up as a milky looking oil if water was getting by the seals. In my mind, this would be of greater concern than a loss of a bit of oil. The water intrusion will cause much more damage.

Airslot · #4 10-21-2004, 02:26 PM

Someone correct me if I'm wrong, but the resevior being referred to is the trim pump. The gearcase should'nt have a res. in the boat. The gearcase can be both pressure and vaccumn checked. Both are done at low pressures.

Airslot

chumbucket · #5 10-21-2004, 10:44 PM

In re-reading his post, I agree Airslot. Remote resevoir tank = trim hydraulics. I still wouldn't worry about it a whole lot.

pk · #6 10-22-2004, 09:57 PM

Hello Again: The reservoir I have on the transom is not for the trim pump. That is a seperate item.
The oil reservoir I am talking about was an option from mercruiser installed by the original owner. It consist of a clear plastic quart bottle mounted in a frame on the transom. A hose comes out of the bottom of the bottle & passes through a fitting in the transom. From there, it connects to the upper vent hole on the outdrive. The purpose of the reservoir, I guess, is to monitor the oil level in the outdrive without having to take the boat out of the water.
There is a procedure in my merc manual for changing out the lower unit oil when the boat is equipped with this remote reservoir. I am thinking that I messed up the procedure and have some air trapped in the lower unit. Over the course of the summer the air vented out and was replaced by oil in the reservoir. Who knows. I am not too woried because oil going out is better than water coming in. I would still like to find out for sure what the problem is. I have a picture of the transom of the boat but I can not figure out how to include it in this reply.
Thanks again for your comments.

chumbucket · #7 10-23-2004, 01:47 AM

Never heard of that option before. ???

#8 10-23-2004, 03:27 PM

[quote author=pk link=board=Repairs;num=1098310530;start=0#0 date=10/20/04 at 18:15:30] ;D

Every year I lose about an inch of oil ( about half a cup or so) from the bottle. *

pk - every year or just last year?

In your last post - it sounded like just last year.

Your explanation of what happened sounds plausible. It doesn't sound like you have a problem, and what little problem you may have had has resolved itself. I don't think I would risk creating a problem with a pressure test. I would just continue the routine maintenance of changing the lube and be glad there is no water in it, or hunks of metal.

Disclaimer: I don't know anything about i/o's. ;D