Mercruiser Alpha One gen2 leaking oil, but where?

[HorizonblueDK]

A friend has a 2006 Campion Chase with a Mercruiser 5.0 MPI/Alpha One, approx 100 hours. Oil is running out, but we can't see where. After a few trips, the drive lube reservoir is empty.

I have pressure tested the outdrive(without oil, 9 psi), after 12 hours it has only lost 2-3 psi.

Oil is apparently only leaking when the engine is running/drive is in gear. When the boat is stored on the trailer at home, nothing is happening.

I have not made a thorough check of the engine compartment, but my friend tells me that there is no oil spill in there.

This oil loss is weird, has anyone experienced something similar before?

 

[Dryon]

Re: Mercruiser Alpha One gen2 leaking oil, but where?

When was it last changed and was it re-filled correctly? Could be air in the unit somewhere that is escaping up & out of the bottle.

 

[HorizonblueDK]

Re: Mercruiser Alpha One gen2 leaking oil, but where?

I took off the drive, drained the oil and pressure tested it. After that I installed it with a new bell-housing gasket, filled it up with oil from the bottom, until it ran out of the vent hole on PORT side. Finally refilled the drive lube reservoir.

 

[HorizonblueDK]

Re: Mercruiser Alpha One gen2 leaking oil, but where?

One other thing, it seems like the oil loss only occurs on longer trips (when the oil gets warmer), nothing happens on a short trip. The oil is of course thinner when it is warm, but since it is original Mercruiser gear oil, it shouldn't be a (the) problem.

I'm a little afraid that there is a crack in the outdrive somwhere, has anyone had that before?

 

[jeepnsam]

Re: Mercruiser Alpha One gen2 leaking oil, but where?

I'm no boating expert...however, i'm in the process of doing my impeller.
There is a "oil passage" with a small oring that sits inside the hole on the lower end. Now looking at the oil port on the upper side..I cannot see how that oring would make a positive seal without the help of some "perfect seal" or RTV. I mean the upper and lower are not machined surfaces.

Is it possible the oring is not sealing due to the vibration on the outdrive on long trips?? And if this is the case, that means the oil will leak out of the weep hole right below the shifter box thingy?? which will eventually allow water inside?

Just throwing my "newbie thoughts" out there.

 

[Hank496]

Re: Mercruiser Alpha One gen2 leaking oil, but where?

Interesting timing on this one. I just got off the phone with our boatyard. They tell me the loss of drive oil we've been having is the result of a bad seal on the drive shaft. It turns out that the seal holds pressure at ambient temperature, but at higher operating temperature it leaks like a sieve.

In our case we were getting oil in the bilge. Apparently the oil gets past the drive shaft seal and collects behind the gimbal bearing and then drains into the bellows. We have to store our boat with the drives up (our mooring is too shallow at low tide), so then it leaks into the engine compartment. It is possible your friends boat may have a bellows that is full of drive oil.

My tech knew what the problem was as soon as the drive came off the boat by the oil dripping out of the bellows.

 

[HorizonblueDK]

Re: Mercruiser Alpha One gen2 leaking oil, but where?

Interesting timing on this one. I just got off the phone with our boatyard. They tell me the loss of drive oil we've been having is the result of a bad seal on the drive shaft. It turns out that the seal holds pressure at ambient temperature, but at higher operating temperature it leaks like a sieve.

In our case we were getting oil in the bilge. Apparently the oil gets past the drive shaft seal and collects behind the gimbal bearing and then drains into the bellows. We have to store our boat with the drives up (our mooring is too shallow at low tide), so then it leaks into the engine compartment. It is possible your friends boat may have a bellows that is full of drive oil.

My tech knew what the problem was as soon as the drive came off the boat by the oil dripping out of the bellows.

You have a good point. But actually I took of the drive when I pressure-tested it. At that time, I hoped that the bellow was filled with drive oil, but no. If it was filled with oil, yes, the mystery was solved, but there was only grease for the gimbal bearing.

But your case is very interesting. Your drive holds pressure at ambient temp, but leaks at higher temp, apparently the same as my friend's drive.

Since the drive shaft seal seems to be ok, I'm suspecting that one of the other shaft seals are bad......

 

[Dryon]

Re: Mercruiser Alpha One gen2 leaking oil, but where?

I took off the drive, drained the oil and pressure tested it. After that I installed it with a new bell-housing gasket, filled it up with oil from the bottom, until it ran out of the vent hole on PORT side. Finally refilled the drive lube reservoir.

You did not state when you installed the vent screw & seal washer. Also, you didn?t state the number of times you had to refill the reservoir.
Did you install the vent screw and then continued pumping until it showed up in the reservoir or did you leave the vent screw out while you filled up the reservoir until oil flowed out the vent hole. If you installed the vent screw and then filled the reservoir, you may have trapped air in the lube monitor circuit. This air will work its way out of the reservoir, which will cause the oil to drop in the monitor bottle.

 

[HorizonblueDK]

Re: Mercruiser Alpha One gen2 leaking oil, but where?

You did not state when you installed the vent screw & seal washer. Also, you didn?t state the number of times you had to refill the reservoir.
Did you install the vent screw and then continued pumping until it showed up in the reservoir or did you leave the vent screw out while you filled up the reservoir until oil flowed out the vent hole. If you installed the vent screw and then filled the reservoir, you may have trapped air in the lube monitor circuit. This air will work its way out of the reservoir, which will cause the oil to drop in the monitor bottle.

I have filled the outdrive twice, just as your first and third description.

Sum up;
First time, filled it up from the bottom, until oil ran out of the vent hole, installed vent hole plug/gasket and continued pumping until the reservoir was filled.

Second time, filled it up from the bottom, until oil ran out of the vent hole, installed vent hole plug/gasket and filled up the reservoir (took off the cap and filled it with oil from the bottle)

After the first time drive fill-up, my friend told me that he re-filled the reservoir once, and when he called me, it was empty again. That means that two times the reservoir volume has vanished.

After the second time drive fill-up, he told me that he had refilled the reservoir a couple of times until the spare bottle was empty (1qt)

From what I remember, the second methode I used, is the one stated in the Clymer manual, but as you mention, there is a risk of an air bubble inside the drive when doing it this way.

My friend has done more boating after the second drive fill-up, so it doesn't necessarily mean that the leak is getting worse, or there is more air trapped inside the drive.

If I start to fill the reservoir, when the vent plug is out, woun't the oil just run out of the hole? The reservoir is higher than the hole, as I remember.

 

[achris]

Re: Mercruiser Alpha One gen2 leaking oil, but where?

There is quite a lot of air space in the top of the drive that can't be remove easily. You could do it by loosening the 4 bolts on the top cover and bleeding it off, but that's not recommended.

That air works it's way out of the system as the engine is used, and on longer trips it will have more air moving out of the system. The space is about 1/2 quart, give or take.

I would suggest that you just fill the monitor bottle each time it gets low and see if it eventually stops. (I suspect it will).

Chris........

 

[cr2k]

Re: Mercruiser Alpha One gen2 leaking oil, but where?

The gen II has a weak spot in the seals. The seals between the upper and lower are plastic seals with NO metal band to help hold them. So there is No real Press Fit just a kinda snug interference fit. It is possible to jar them loose when stabbing the lower after an impeller change or something similar.

And as luck would have it, you need to dissemble the upper to replace the seals.

Not sure what else can cause this but we have seen 3 gen IIs with this problem.
Hence when we have to reseal that area we run a bead of Cya (superglue) around the seals.

I am starting to wonder if the greatest advantage of the gen II is to the factory in the cost and ease of assembly, and not so much operational improvements.

I will give them the water pump.

 

[Dryon]

Re: Mercruiser Alpha One gen2 leaking oil, but where?

If I start to fill the reservoir, when the vent plug is out, woun't the oil just run out of the hole? The reservoir is higher than the hole, as I remember.

Yes, it will flow out the vent hole and this is what you want it to do so it can force the air out of the monitor curcuit. It takes two people to do this, one at the lube bottle & one at the outdrive. Once a solid stream of oil starts flowing out the vent hole the person at the outdrive quickly installs the vent screw & seal washer. There still will be some air, but not as much as you would trap if you don't remove the vent screw before filling the bottle.

 

[jeepnsam]

Re: Mercruiser Alpha One gen2 leaking oil, but where?

Here's an Idea that I will try this weekend:

- pump gear oil from drain oil
- plug vent hole when oil starts to come out
- have 2nd person watching the reservoir bottle as I pump gear oil from the drain oil.

This should remove most if not all of the air.

 

[achris]

Re: Mercruiser Alpha One gen2 leaking oil, but where?

Here's an Idea that I will try this weekend:

- pump gear oil from drain oil
- plug vent hole when oil starts to come out
- have 2nd person watching the reservoir bottle as I pump gear oil from the drain oil.

This should remove most if not all of the air.

It will not. There is a large air pocket between the vent plug hole and the top of the leg, The feed for the oil monitor is at about the same level as the vent hole. There is only one thing that gets all the air out, using it....

I have had 2 Gen II legs over the past 16 years, and look after another 5 for friends. This is completely normal for them after changing the oil. As long as you put the quad seal in when you put the leg back together, used a new seal on the drain and vent screws and there is no oil in the bellows everything should be good. Just give it time and you'll see that the oil 'loss' will eventually stop.

Chris.........

 

[HorizonblueDK]

Re: Mercruiser Alpha One gen2 leaking oil, but where?

OK guys, I think I have solved the problem.

My friend told me that he had noticed oil coming out of the water intake, so I suspected a leak in the shaft seals, under the raw water pump.

Took the drive apart, removed the pump, pulled off the seal carrier and guess what happened?

One seal fell out?! and the other was placed at an angle of approx 15? in the carrier....

I have now installed new seals and assembled the drive again. Pressure tested it over the night with 9 psi. This time it is 100% leak free.

When I tested it before, it lost 3 psi over the night, but from I what I remember, that is within the specs.