Small amount of water in leg oil of Merc 225 Opti

[Rockfish]

A trace of water in the leg oil of my 2001 Merc. 225 Opti.

Every spring we drain the leg oil and replace and last year we noticed a small amount of coffee color ribbon of color on the dark dirty oil in the catch basin where we drained the leg oil. Since the motor had not been run over the winter and oil floats on water it was noticed only for a short time when the oil started to drain. I am curious as to how serious this is and the best course of action. We ran it for the season without a problem. So the options now seems to be drain it and have a look and if it is the same keep running it next spring or see if I can get a Merc mechanic to remove the leg and service it - new seals possibly a bearing or two etc.

The motor currently has about 900 hours on it and the previous owner had a seal and bearing replaced before I bought it. It had about 600 hours on it when I got it.

I did talk to a couple of Merc. Mechanics when we noticed the little bit of water and they did not seem to get excited about it and one commented that the oil is a very good lubricant even with a little bit of water in.it. The leg oil additives bond to the surface of parts and one commented they had a guy run a motor for 150 miles by mistake with no oil in the leg and when they took it apart it was just fine from the oil film left on the parts. Obviously not a good thing to do but still somewhat reassuring.

I am leaning towards having the seals etc. done. Any thoughts?

 

[scott craven]

It is usually the prop shaft or shift shaft seal that allows water intrusion.
You could also try replacing the gasket of the oil drain bolt.
a small amount as you describe won't likely hurt anything.
I would change the lube more frequently to monitor it.

 

[willydw]

It is usually the prop shaft or shift shaft seal that allows water intrusion.
You could also try replacing the gasket of the oil drain bolt.
a small amount as you describe won't likely hurt anything.
I would change the lube more frequently to monitor it.

I had a problem with the oil drain bolt gasket also. That is where I would start before spending a pile of money.

 

[Tightlines22]

Gear oil is so inexpensive. As others mentioned change it more often and keep an eye on it. At some point you’re gonna need new seals. Not overly difficult to replace.

 

[Rockfish]

Thanks guys. In our case we mostly just use it for a few minutes to get in and out of the harbour (no need to go farther with the massive new whale closure zone taking away 85% of the Sooke fishing area) and I doubt we put more than about 13 hours on the Opti this past season. I don't like putting hours on the main so even when we go to the crab traps on the way in we shut down the main and start up the kicker while we run around pulling the traps. Only takes a few seconds to switch over motors as the kicker is full remote and instant start. I am thinking changing the leg oil on the Opti more often than about every 13 hours will not make much of a difference. I guess we will know more when we drain the leg in the spring.

 

[wolf]

I would drain it now and see if there is any more and replace it now as if there is a bigger problem easier to deal with over this whole winter then in spring WHEN all the shops get smoking busy..

 

[Rockfish]

I would drain it now and see if there is any more and replace it now as if there is a bigger problem easier to deal with over this whole winter then in spring WHEN all the shops get smoking busy..

Good points. I thought about that but was concerned it would still be an emulsion of small micro particles of water suspended in the oil. I know that when there is a lot of water in leg oil in a motor that has been recently run, that it looks like a cloudy brown milkshake. When we did it last in the spring, it had the winter to separate out with the little water coming out from the drain first. If it is still an emulsion I am not sure how I would tell how much water is in it, unless it was very milk shakey which would indicate a major problem. If it is just a very little amount of water however, I am not sure it would show up much at all. So a question for the experts; how much time needs to pass, for the motor to sit unused, for a little water to separate out of the leg oil and sink to the bottom?

 

[dss]

I change my gearcase oil every fall. That way if there is any water in it it does not sit in the gearcase over the winter so no water near the bearings for the winter.

 

[beemer]

not a problem , check to make sure you don't have two gaskets on the drain bolt , happens a lot . Use a fresh gasket and give a good clean around the hole!

 

[scott craven]

I am not sure it would show up much at all. So a question for the experts; how much time needs to pass, for the motor to sit unused, for a little water to separate out of the leg oil and sink to the bottom?

Water will separate from the gear oil quickly.
If there is any at all you will see it run clear before the dirty oil

 

[gungadin]

Pull the prop, check for fishing line behind the thrust washer. If the seal has been compromised there may be a little oil residue on the seal face. Drain the oil, fill the leg with cheap engine oil, run the engine for a few minutes, with the prop off and in gear. Drain the oil again, for about 15 minutes tilting the leg so the drain hole is at the lowest point, refill the leg with recommended leg oil using new seals (gaskets) lubricated with a little oil. If you decide to fix it have the mechanic pressure test the leg to pinpoint the leak. He will need to pull the leg so might be a good time to check the water pump as well.

 

[beemer]

If you want to DIY pressure test your prop seals you don't need to take off the leg. Attach your Gear leg oil refill insert onto a bicycle pump (really) and pressurize the leg. (about 20 pumps) spray some soapy water around the prop seals .Bubbles mean new seals and mo money.

 

[gungadin]

If you want to DIY pressure test your prop seals you don't need to take off the leg. Attach your Gear leg oil refill insert onto a bicycle pump (really) and pressurize the leg. (about 20 pumps) spray some soapy water around the prop seals .Bubbles mean new seals and mo money.

Water can enter the lower leg in several ways, in order to pressure test the leg you will need to drain the oil from it and remove the lower unit as well as the propeller. You will also need to remove the water pump. You need to be prudent about the air pressure though or you may actually precipitate a leak. Certainly do nor exceed 10-14 psi. Areas to spray soapy water include both filler and drain plugs, propeller shaft seals (inner and outer) shift bellows and seals and drive shaft seals (under the water pump). Be sure to rotate the shafts and wiggle things around as you are checking for bubbles as the ingress of water is slight in your case.

 

[Rockfish]

Thanks gungadin, it sounds like you have done a lot of these. By any chance are you on South VI?

I am going to let any water separate out for a couple of more weeks and then drain the leg and see what it looks like, then pull the prop. and take it from there.
We could easily change the filler/drain seals and perhaps the outer prop seal - not sure about the outer prop seal which I understand is often the cause of this issue. Beyond that I am thinking it would be best to get a pro. with a lot of Merc Leg experience. At getting closer to 900 hours, would it be over kill to just have the leg removed and the water pump and all seals and bearings replaced?

I have a smart computer controlled digital air pump that I can set to stop when a specific pressure is reached, so if we set it for say 8 lbs I assume that would be a safe test pressure. However we would need an adapter for the filler/drain port and I have no idea where to get one unless we could use or modify the one used to pump in the leg oil. Further if the leg has to come off we may be back to having a pro do the more expanded work?

 

[Charlie415]

At getting closer to 900 hours, would it be over kill to just have the leg removed and the water pump and all seals and bearings replaced?

In my opinion this would be over kill. If it was a major amount of water then further checking would be prudent. With the amount of water in your oil reseal after determining bad seal, new oil then an oil change after running it 25 hours or so to verify no more water in the oil.

 

[gungadin]

You have the almost all the equipment to pressure test your lower leg. You just need a couple more things:

https://www.amazon.com/Shoreline-Marine-Pump-Lower-Unit/dp/B07J6TP7X7, it about 10$ at a local marine store and

https://www.amazon.com/Vixen-Air-In...qid=1541121691&sr=8-8&keywords=schrader+valve, often you can go to a tyre repair shop and get one that would work

Take the hose off the pump and attach the schraeder valve using a clamp to hold it on. Remove the prop, drain the oil, install the filler end into either the fill or drain port of the leg and put a plug in the other. Pump up to 8psi and disconnect compressor. spray wherever it might leak with soapy water. If you cannot detect a leak just let the leg sit under 8psi ans see how long it will hold it, should hold for about two min. if not, you will have to pull the lower section off and recheck with the water pump removed. if it does hold up, raise the pressure to about 11-12 psi and retest. I certainly second sin bin's assertion that it would be overkill to replace all the bearings without pinpointing the cause. You might be spending much more then you need too. Hopefully you have had the leg off in the past, or that task may be be your first "sticking" point.

 

[Rockfish]

You have the almost all the equipment to pressure test your lower leg. You just need a couple more things ...
Hopefully you have had the leg off in the past, or that task may be be your first "sticking" point.

Thanks, - very useful info.
The leg was last off about 5 years ago when I had a pro mobile marine mechanic pull the leg and replace the water pump and the zincs while he was at it. I think he also pulled the prop. Funny story, we have replaced the zincs many times ourselves with no problems but the time I have a pro install the zinc under the cavitation plate it vibrates lose and falls off under power and in the process puts a few very small dents on the edges of my very expensive 4 Blade SS prop. blades. Good thing it was SS and not an Al prop as I am pretty sure it would have destroyed an Al prop. Since we have to pull the prop anyway I guess it is a good time to take it to a prop shop and have it cleaned up and tuned over the winter.

I think we already have everything needed but the Schrader Valve to do the pressure test.

Is changing out the outer prop seal on the big Opti a simple job we can do ourselves without a lot of disassembly or specialized Merc. tools?

 

[Charlie415]

Thanks, - very useful info.
The leg was last off about 5 years ago when I had a pro mobile marine mechanic pull the leg and replace the water pump and the zincs while he was at it.

If it was me I would be checking the leg more often than every five years. I check mine every year, but depending on usage I would not let it go longer than 2 years. Left to sit corrosion will not be your friend. Even if you aren't putting on hours time is not your friend.

 

[gungadin]

Is changing out the outer prop seal on the big Opti a simple job we can do ourselves without a lot of disassembly or specialized Merc. tools?

A short answer is no, it is not a simple job. It is possible to change the outer seals, but there is a possibility of scoring the surface of the bearing carrier if you are not careful, which would probably result in a leak when reassembled. To remove the bearing carrier you need to undo the large nut that is retaining it, and when time comes to reinstall the nut it is done up tight about 200 lbs/ft if memory serves. There is a special tool for this, you then need a puller to remove the bearing carrier, depending on the amount of dried salt holding it in this can be a bear. It can be done in situ using a screw and a slide hammer, but with the associated risk of scoring the surface. That is the bad news, the good news is the seals under the water pump and shift collar are much easier to replace.

The story you tell about the zinc under the cavitation plate, raises a red flag for me as you are using a stainless prop. There is a possibility that you may have bent ( be it ever so slightly) the propeller shaft. Easy to check. Remove prop if necessary, level engine over flat surface, screw a short piece of 2x4 to a longer piece so that when the longer piece is laid on the ground the shorter piece goes vertically about an inch up past the end of the propeller shaft. put a sharpie mark on the shorter 2x4 so that it is in the middle of the shaft. now turn the shaft by hand and in neutral. if you can see the shaft moving up and down from your mark on the wood, the shaft is bent. If it is bent at the area where it goes through the seals, it could be causing your leak.

 

[Rockfish]

Is changing out the outer prop seal on the big Opti a simple job we can do ourselves without a lot of disassembly or specialized Merc. tools?

The story you tell about the zinc under the cavitation plate, raises a red flag for me as you are using a stainless prop. There is a possibility that you may have bent ( be it ever so slightly) the propeller shaft. Easy to check. Remove prop if necessary, level engine over flat surface, screw a short piece of 2x4 to a longer piece so that when the longer piece is laid on the ground the shorter piece goes vertically about an inch up past the end of the propeller shaft. put a sharpie mark on the shorter 2x4 so that it is in the middle of the shaft. now turn the shaft by hand and in neutral. if you can see the shaft moving up and down from your mark on the wood, the shaft is bent. If it is bent at the area where it goes through the seals, it could be causing your leak.

Thanks again. I will check out the shaft, although I am hoping that if that were the problem, that it would have showed up faster than a very small amount of water turning up after 4 years of use since the zinc fell off and there has not been any drive vibration etc. Not sure I would be able to tell the difference between a very slightly bent shaft movement and movement from say a bad bearing, or how we could manually turn the shaft with the prop off. I suspect that comes with experience.
Perhaps we will get lucky and there won't be any water trace in the leg oil when we drain it, as we did put in new filler and drain seals last time.