Lower Unit Advice Bad Seal

[bruce]

" I bought a 2000 50HP 2-cycle

" I bought a 2000 50HP 2-cycle Yamaha this past spring. Call me foolish, but I did not check the lower unit oil upon the purchase. I ran between 50 and 100 gallons of gas this summer, and winterized the motor this past weekend. The gear lube was the color of buttermilk, but felt fairly viscuous and was consistent (no lumps). There were no metal particles on the drain plug, just a tiny bit of black sludge. I didn't measure the amount of oil drained, but it seemed like it was probably the full amount. I refilled the lower unit with fresh oil.

I figure I will run the motor next spring and check the oil and see how it looks. I don't have any idea of the maintenance history of the boat or if it had been winterized by the previous owner. He told me it had been stored in his shop.

Does anyone have any comment about my intended course of action or any ideas how water may have gotten into the oil. If the seals need replacement, how much would one expect to pay to have the work done, or what is the level of difficulty in performing the work myself?

Thanks for any input. "

 

[jon]

" Bruce,

I can't speak

" Bruce,

I can't speak as to exactly where it's probably leaking from; there's going to be a seal where the driveshaft enters the lower unit (under water pump) and another where the shiftshaft enters; lastly, there is a seal around either the prop-shaft and/or bearing carrier and some O rings/gaskets around the drain/fill plugs. If it's anything other than a seal around the prop-shaft/bearing carrier you probably aren't looking at very much work; the least likely is that it is that seal and it takes a bit more knowledge and possibly a tool and/or creativity to get in there.

For a quick test, drain the lower unit; put your finger in the vent hole as to close it off, screw the gear lube pump into the fill hole and pressurize the lower unit a bit by pumping some lube in. Listen for the hiss of a leak - you should feel the pressure release when you take your finger out of the vent hole. If you don't get any sign of leakage doing that, it can't be too bad. It's up to you how far you want to take it, checking the seal around the driveshaft/shiftshaft might not be a bad idea - pull off the lower unit and do what needs to be done to get in there and take a look.Be sure you have been using new gaskets/O rings on those vent/fill screws.

A small amount of water getting in over time isn't going to hurt anything, but if you allow it to drain itself or get too much water in, unchecked it's going to lead to corrosion, and/or eventually lower unit failure. If that engine is left in the water, it could be sucking small amounts of water in during temp changes (cooling).. if it has a legitimate sealing problem, this would be worse.

My .02, I don't keep my boat in the water, it's dry docked most of the time. I've got a slow lower unit leak of some nature and I just run cheap gear lube and change it often. If it gets so bad that one trip out will make watered down gear lube, I'll fix it. This isn't the first I've treated this way, for an extended period of time, without a problem. It hasn't caused any problem and probably won't, but I realize that I have to at least check it before every trip. It works for me, but if this boat was moored up somewhere and not in the front yard, I'd probably have to bite the bullet and fix it for good.

Jon "

 

[bruce]

" Thanks Joe.

My boat is &#

" Thanks Joe.

My boat is "dry docked" in the yard and always is except when I take it down to the coast where I rent a slip for a week and keep it in the water.

Like I said, I didn't check the oil when I bought the boat, so I don't have a "baseline" to see how or if the problem has escalated. I did not change the gaskets on the fill/drain plugs when I changed the oil. I guess I will change those, and then run the motor next year and check it frequently to see how bad the problem is.

I filled the lower unit with Yamaha gear lube - do you consider that an unecessary expense? The lube is sold in 11 oz. tubes and gallon jugs. I need about 15 oz. to fill mine, so that's 2 11 oz. tubes at 5 bucks each. If I were to buy the gallon for 25 bucks, that's enough lube for 8 changes. How long does an opened container of lube last in storage before breaking down? "

 

[tonyob]

" Bruce,

One point I would

" Bruce,

One point I would like to add here is that better gear lubes will tolerate quite a bit of water without any problem. I use Quicksilver high performance lube in everything, because I know it holds up even if some water works its way in there.

Cheaper products will become very thick with just a tiny amount of water getting into the gearcase.

Tony "

 

[jon]

" Bruce,

There's d

" Bruce,

There's definitly a big difference in the quality between the cheapest and the factory brands. As tony said, the better brands hold up better with a little water in em; I've actually noticed this as well. I honestly change my gear lube a good 20+ times a season and use the cheap stuff because it's a difference of almost $5 a quart; although with the better stuff I probably wouldn't have to change it so often, for me knowing the gear lube is full and clean is more piece of mind. I'd say since you are getting very little water in there, it'd make more sense to use the quality stuff, as in the long run you wouldn't be saving much anyway. Also, as this engine does live in the water for a week, you aren't going to be changing or checking it and for that you want to better the odds of it holding up.

As for the length of time lube will last in storage - as long as you aren't getting impurities in there, a VERY long time. Oil really doesn't break down that easily, this season I got cheap and creamed 2 gallons of 10+ year old Mercury 2-cycle oil, one container had even been opened and they bothe sat outside for atleast 2 years; it caused no problems. With gear lube, it doesn't have to burn, so it's going to last even longer - probably nearly forever if sealed.

Jon "

 

[sparky]

Pressure test the lower unit

Pressure test the lower unit and find the leak. Yamaha seals are rubber coated and if there is water in between the seals in the winter the combination of ice and less "grip" due to the rubber being hard when cold will shift one or both seals. In the spring leakage results big time.Just something to look at.