Water in Lower Unit

[Juan Grande]

So I drained my lower unit lube today and as I undid the drain bolt, water gushed out before the oil. Oil does not appear to be leaking from the lower unit, but obviously water is getting in there somehow. Just wondering how I should go about handling this? I assume I could bring it to a marine shop and have them diagnose where the leak is? I would assume the leak is above the resting level of the oil since it's not leaking oil when parked.

The boat/motor are six years old so I wouldn't think it would be from an old seal or something. There was an "incident" at the launch this summer where my boat ended up rolling off the trailer and hit the pavement pretty hard, landing on the skag. At the time, it seemed to run fine and there was no visual damage other than a chipped skag. I'm guessing more damage was done than I though and that's what caused this leak.

Should I fill the lower unit lube for winter storage or leave it empty? I will probably bring the boat in to be looked at in the spring.

Any advice would be greatly appreciated.

John

[toughguy]

I've got an '02 90 HP Merc and I've always had water in my lower unit at the end of the year. I assumed this was normal. There isn't a lot of it but a little water (about 2% of what comes out) always comes out first. I was told this is why you change the lower unit oil in the fall and not the spring - if the water is left in there it would freeze and cause potential damage. I'm no expert I'm just stating what I've seen in my motor for the past 8 years so far with no major repairs needed.

I would put oil in for the winter rather than leaving it dry. Check for leaks in the spring

[Basscat]

Usually the seal around the prop shaft is what allows the water in. It is possible that there is a crack somewhere, but you should be able to see it. I would have it full of oil while storing, just to prevent any chance of rust forming.

[Dellfin]

Best to have that checked by a pro to see if there a hairline crack somewhere allowing water to seep in.

Also, remove the prop and check to see that you don't have any fishing line wrapped around the shaft. That stuff can wreck the seal and I hear it's pretty common spot for water to invade the lower unit.

[toughguy]

Sometimes there are rubber rings around the screws that keep it water tight. Make sure none of the rings are cracked or missing.

[Juan Grande]

I checked the rubber rings to make sure they weren't damaged. They all seemed to be okay so I lubed them with oil and put them back on. I think there must be a sizeable leak considering how much water was in it and the fact that I only have the boat out probably once a week in the summer.

[marine_man]

If your schedule allows I'd get it in for repair now when dealers aren't nearly as busy as they will be in spring.

marine_man

[Juan Grande]

I had the insurance adjuster out to look at it and he thinks it's just the rubber gaskets on the drain and vent plugs. He said he had the same problem with his motor and after putting in new seals it was water tight. I'm going to swap those out and then run it in the spring and drop the oil again to check for water. Hopefully it will be clean.

Thanks for the tips guys!

[marine_man]

Do yourself a favor and pull the prop.. make sure there's no fishing line wrapped around the prop shaft by the seal. If you find line there, I'd be inclined to get it in for a pressure test before I put it away. It won't do any harm if you replace the oil and wait till spring... but you also won't have to wonder about it all winter and spring either.

marine_man

[nocturnalmotors]

Usually the seal around the prop shaft is what allows the water in. It is possible that there is a crack somewhere, but you should be able to see it. I would have it full of oil while storing, just to prevent any chance of rust forming.

+1... and check for line around the prop shaft behind the prop. That's usually the root cause.

[Juan Grande]

The motor actually landed on the skag so I don't think there was any damage to the prop, but I'll take it off and check for fishing line. I replaced the drain plug and vent plug gaskets and refilled it with oil.

Thanks again for the advice.