lower unit drain and refill--flush?

[Motor Boater Bill]

I have a 1976 20 hp Merc 200. I bought it used. I have drained the lower unit and am going to refill it with fresh grease, but I was wondering if I should flush it out with something first. The grease I drained out was not entirely clean, I'd call it cloudy, about the color of peanut butter, but no water and no metal (checked with a magnet). Thanks!

 

[gss036]

Re: lower unit drain and refill--flush?

If it was peanut butter color you have a little water mixed with the oil. Change it and recheck after a few trips. Messy but a simple job.

 

[Motor Boater Bill]

Re: lower unit drain and refill--flush?

What about flushing it with something before refilling it? I have seen references to using either kerosene or mineral spirits for this, but I don't want to damage the seals or contaminate the grease I refill it with. Any suggestions?

 

[dajohnson53]

Re: lower unit drain and refill--flush?

Motor boater bill, it's oil you're using in the lower unit, not grease. I just say this because someone might question whether you're indeed putting oil into it. It's a little heavier oil than automotive motor oil, or 2 cycle oil, about the same as what is called gear oil or gear lube in cars. But it's nowhere like grease.<br /><br />As to flushing. I have used regular motor oil or 2 cycle oil to flush out a lower unit, figuring that if it drained completely, any residual left over would be a meaninless amount when I refilled with lower unit lube. Or, if even that worries you, why not just fill it up with lower unit lube, maybe turn it over or run it a little (w/hose of course), then drain and refill with new lube? The amount of oil wasted will be very small. I can't see the reason to flush out with solvent (mineral spirits, etc).<br /><br />By the way, the sort of condition you have seen (contamination by water) is fairly common so it's not an unusual situation. Like the guy said, keep an eye on it - check it after the next run to see if it's getting conatminated quickly (in which case you probably want to find the problem). Good luck.

 

[Motor Boater Bill]

Re: lower unit drain and refill--flush?

Thanks, D. I am using Quicksilver Gear Lube (I can never figure out whether to call it grease or oil).  The batch I just drained was "Quicksilver Super Duty Gear Lube" from an older tube I had, and which I didn't see at the dealer this time.  I refilled with "Quicksilver Premium Gear Lube" which I suspect is more or less the same stuff--it is what the dealer recommended. <br /><br />I am not sure it was totally empty the first time I filled it, so it might have been contaminated my whatever was in it (unknown, bought the motor used). This time I drained it overnight and turned it over in gear, so I think it was pretty empty. I plan to go out for a day on the river, about 1-1.5 hours of running and LOTS of fishing, then change it again to see how it looks.<br /><br />Thanks to all here for the help--great site. Between this board and John's Old Mercs, I've been able to keep my old motors going strong!

 

[dajohnson53]

Re: lower unit drain and refill--flush?

My opinion on lower unit gear lube is that any Marine grade lube with the right spec is good, especially for a small kicker. Most important thing is to keep the water out of there. Good luck, have fun fishing (I'm still a$$ deep in snow).

 

[Motor Boater Bill]

Re: lower unit drain and refill--flush?

Some of our best fishing here in KY is in the tailwaters below a big dam, so we can fish that all year. I caught the two biggest trout of my life this winter. Let's see, I need to tie this back into motors--oh, yeah, when I caught the big one it almost caused a lower unit leak!<br /><br />Tailwater fishing is why I moved up to the 20 hp motor--my old 9.8 had to work too hard when they were generating and we needed to motor upstream with three of us in the boat--go faster upstream=more fishing time!

 

[dajohnson53]

Re: lower unit drain and refill--flush?

Originally posted by Motor Boater Bill:<br />Some of our best fishing here in KY is in the tailwaters below a big dam, so we can fish that all year. I caught the two biggest trout of my life this winter. Let's see, I need to tie this back into motors--oh, yeah, when I caught the big one it almost caused a lower unit leak!<br />

Ah, a high "big fish, lower unit pucker factor", my favorite kine.<br /><br />

Tailwater fishing is why I moved up to the 20 hp motor--my old 9.8 had to work too hard when they were generating and we needed to motor upstream with three of us in the boat--go faster upstream=more fishing time!

I don't think there is such thing as too much power (properly used of course!). I'm thinking having decent power in the vicinity of a dam would reduce the "will the motor get me out of this pucker factor" and make for more relaxed fishing as well as more efficient.

 

[Motor Boater Bill]

Re: lower unit drain and refill--flush?

Well, since we fish below the dam and upstream from the takeout point, the default is always to just float back to the ramp. We usually resist the temptation to go downstream on the hope we can make it back up with our floatilla of ancient boats--my 1962 9.8 was the newest one of the bunch until I got the 1976 20 hp. The best trip is to drop cars 15 miles downstream and spend all day floating it. But on the days we fish the four miles from the ramp to the dam, being able to motor up more quickly will definitely increase the fishing time!