I have a problem with a drive that is proving difficult to diagnose and I have a major time issue. I have Imco Extreme SC drives and one of them is making oil. Not milk shake-no water in oil. After a short run it builds pressure in the reservoir tank enough to blow the cap off. Drive has proper amount of oil and the cap is the same one that has been on for two years and looks good. Anyone have any ideas as we are stumped.

David

do you have coolers? Sounds like a temp problem

Do not have coolers. And, the other side has no issues nor did this one before now.

Db

What kind of power?

I never noticed that problem with mine, pushing 800hp through it.

Are you sure it is filled completely? Sounds like air is in the drive and expanding when getting hot.

I had a friend with the same problem on an XR. Finally had it completely taken apart and then reassembled checking tolerances very closely. All was fine after that.
It is definately getting hot and causing some expansion. I would bet it is on the LH rotation drive. They always get a little hotter.
The merc reservoir caps are designed to only let air in and they do not allow for any expansion to let air out. I think you may have some air pockets and the combo of heat and expansion is causing the issue. The lube won't really expand under heat, but the air mixed in will. I would drain the lube and fill it very slowly with the pump to ennsure that air is removed.

Second seen this happen drove us nutz, told my buddy cheapest thing to do was to drain it completely, (even the waxy build up at bottom of resovoir) and refill slowly and ccorrectly making sure nothing was clogged or air in drive, I think last time he changed drive oil he allowed some to leak out before he got the hole plugged (causing problem). problem fixed.

Change the cap before you try anything else.

The reservoir cap?????
The cap is only designed to let air in so the lube can flow to the drive if needed. It is not designed to release air out of the reservoir.

Thanks guys. Very helpful. The cap is one-way as stated and in good condition. We are taking the drive off today and completely dis-assembling it to check exact tolerances. Also, for excess air. I hoping something is out of tolerance and that will take care of it. Dave at IMCO says it is either that or the tower/case could be out of true. Not so good. Should find out today and will post what we find.

I am running 750hp through them but with 42' in front. They are certainly my weak point but have been ok, so far. The original problem with this one was this side drive trim switch decided on it's own to go up into trailer mode when I was underway running about 70mph. I wasn't expecting that and when it came out of the water and I pulled back the throttle it was too late. Good bye drive upper and yokes. This pressure problem has been since re-assembly.

Hoping to run with Team Predator to St. Martin next weekend so we on it.

Thanks again,

David