1986 yamaha 150 outboards lower gear lube and quantity

lime4x4

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#1
Time to change the lower gear lube in both of my 1986 yamaha 150 outboards. Can't remember how many quarts i need to do both outboards. Also was gonna use yamalube gear case lube 80w-90 anything better?
 

seasick

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#4
For my 150 the LU takes a bit more than a quart, something like 1.1 qts, an annoying value that forces you to buy 3 bottles of oil. I wouldn't use synthetic, the Yamalube is fine. Don't forget to get new gaskets for the oil plugs.
 

DennisG01

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#5
Some synthetics should NOT be used - or more specifically, any GL5 rated lube should not be used in certain lower units. The Merc synthetic is GL4 and is a fantastic gear lube. It's only a buck or two more per quart - it really is good stuff. I've been using this stuff in pretty much everything for a couple decades. Not that the regular Yamaha or even another manufacturer's regular stuff is bad - but the Merc stuff is a step up in that if you don get some water in there, it will still protect the gears. The regular stuff will not fair as well.
 

Doc Stressor

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#6
I'll second the recommendation for the Mercury High Performance (not their Premium) gear lube. I used that stuff in my old Honda BF90 and the original lower unit is still running fine after 21 years. That span includes a couple of leaky seals and few propeller shreddings. It's GL4 to protect soft metals and it seems to hold up well during water leaks until things can get repaired.