Lower unit fluid

rasbury

Howdy, there have been a lot of threads recently on lower unit issues, perhaps we should have a section just for that?

I have a bravo III, 2005 and around 200 hours on it. Recently had an issue with the prop shaft seal which was replaced as it had a little leakage going on.....I noticed in the service manual the way the line comes through from the reservoir there is what is called a dribble valve. when the lower unit is removed and before it is put back on, it states to fill the reservoir and then push in on that valve to get the fluid flowing to purge the air-then install the lower unit so you don't have air in the system. Well, my repair was more like a change of fluid as the lower unit was not removed. I do not have any visible leaks going on and expected to add some fluid as the system absorbed the gear oil. I have probably re filled the reservoir completely once as I have been keeping an eye on it and topping it off a little at a time. What is normal here, where else can it be leaking that I would not see it? I have a friend that has been a mechanic for many years, worked as a service manger at a loca boat place as well and he says something about the connection in the transom can be leaking and "filling the boot" which I do not get at all looking at the manual....at some point he said where ever the fluid was leaking in, it would fill and eventually spill out into the bliege which I have not seen yet.... what is up with this lower unit???

Dream_Inn

If it was leaking and filling the boot (bellow), then it would more likely be the upper seal leaking.  Across many boats, I've seen many different leaks.  Another one is the connection where the reservoir connects at the transom.  I've seen mechanics not connect them properly (not clicked in) and they come off & leak.  Ras, you trailer yours, correct?  have you ever noticed after a week or two any oil on your drive or under it?  I know some leaks have to be under pressure, so maybe remove the drive for a pressure test would be best.  You really should not be losing fluid in the reservoir.  I can go an entire boating season maybe putting 70 hours or so on it and maybe add 1/2 inch in the reservoir total.

rasbury

what about after a fluid change? There is nothing leaking under the boat, that's for sure...it was before when the prop shaft seal was leaking but nothing there now. I have reached around inside as best I could and could find no leak. I guess for now as long as I keep an eye on it, it''s leaking between the reservoir and the foot and not the foot so it should not be taking on water or running out.....will keep an eye on it and keep futzing around with it until I figure it out. My buddy says we can do a pressure test on it mounted and at least confirm a leak from the transom forward or the transom back...

Dream_Inn

Ras, after a fluid change you will have it go down a bit.  I do mine in the fall, so I top it off in the spring.  This year is a bit different since my boat happens to be on land.  I changed the oil in the one last weekend as well as the reservoir of the other.  & the other one will have new fluid as well.  I'll try to let you know how much it goes down now, but in the past after a change it's no more than half the reservoir.

Definitely best bet is to watch it and make sure it doesn't change color, especially more milky (like chocolate milk).  That would indicate water is getting in.

rasbury

and I may have only done a half as well.....I topped off a couple of times so that may be about right! I just get very nervous....always expect the worst!

mvn

On the Alpha after a fluid change, I have to top the reservoir off about 1/2" after the first run then that's about it for the season.

Mark 

Michael T

@Ras there is usually air in the system after a gear lube change and it will "burp" once or twice requiring a top-up but that's (IMO) normal.