Drive Lube Loss
 

Towards the end of last season I had an Imco -2" shorty installed on my Donzi 22 Classic 496 Mag, Bravo One. As soon as the new lower unit was installed, I noticed about a 2 ounce per 3 hours of usage, loss of drive lube as indicated in the reservoir.
There's no indication anywhere (inside or outside the boat) that there's a leak.
I've since learned that there's something called molecular compression that could be causing it, as well as if there is a leak, the drive lube could be accumulating in the bellows, and wouldn't necessarily show up until the bellows starts to overflow the leaking drive lube.
Anyone know how much lube would have to accumulate in the bellows, in order for the lube to start overflowing into the bilge?
Any opinions as to whether I should just keep an eye on it this upcoming season (since the loss is very minor), or have the drive pulled and pressure tested?
I changed the lube at the end of the season (had around 12 hours on it) and the lube looked like new.

If the drive was filled from the bottom only and then installed, it will continue to use some lube for the first few hours. What's happening is the air in the top is being replaced by what's in the bottle. To minimize this, once filled to vent, lay drive in its side with vent hole up. Now either pump some more in until full, or pour it in thru the vent hole until full.

Now if you did this and your loosing lube, just pull the drive and find out now

That was my initial thought, but after 12 hrs of usage, you'd think the air would be out of the system by now.

You can pressure check it while it's still on.

I have a Bravo 3 and change drive fluid at the end of each season. During the winter I routinely visit the boat and rotate the props- trying to get the air out. Every spring I have to fill the reservoir with oil and then after a few hours of "real" run time. I have the drive pulled every other year for engine alignment and anything that maybe found. Pressure testing has been negative- nor has there ever been a leak of oil - However, during the summer I notice that I have to put a few ounces in the reservoir. It is my understanding that there is a partial vacuum created which will remove some of the oil out the prop shaft- NOT VOLUMES - a little here and there.

Just my experiences.

3pointstar

It can leak through prop seals under load and you dont see it. Either that or into bellows.

Take the rubber clamp off the bottle and look underneath and see if the sensor or nylon barbed fitting is leaking.

Drain the oil and pull the hose off the lube bottle and put about 5 lbs of pressure on the entire system ...see what happpens .... if it holds you can rotate the propshaft a cpl of times to see if it will leak past the seal ....m

if the fitting is leaking you should see oil in the bilge ...Had one leaking and oil was getting into the bilge so was thinking driveshaft seal ...pulled the drive and bellows was dry and drive passed pressure test .... ended up that the rubber washer in lube bottle cap was missing ....:)

There's no sign of a leak anywhere. The bilge is clean as a whistle, as well as the Motor. I've left it in the water for a while after running it hard, and there's no rainbow or anything that would indicate an external leak.
It's just odd that it started loosing fluid (albeit not much) immediately after I had the Imco shorty installed. Prior to that it never lost a drop.