OIL CHANGE MERC 3.9

[KENNETH BROWN]

What is the correct procedure for changing lower end oil in Merc. 1966

[crosbyman]

remove the gearcase lower fill screw remove upper vent screw

fill with 90 grade oil from the bottom with a squeeze bottle to push out the air out the top vent screw

when oil comes out the top screw… just plug it shut to create an air lock

remove the fill bottle and quickly reinsert the lower fill screw

p.s. always better to replace the nylon washers with new one and do check the used oil for contamination with water (coffee colored oil indicates water leaking into the gearcase and the need to reseal the gearcase ..some just change the oil half way during the fishing season.

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[billw]

Mercs prior to about 1976 had steel shafts. They have a strong tendency to rust, get pitted and rough, and destroy the oil seals, particularly the one under the water pump. If your lower unit is still operational, lucky you! Until such time as it can be repaired correctly, which is quite a feat, I would change the gear oil after every single use of the engine. Believe me; I have been doing this for a living for a longggggggg time.

Long live American manufacturing!

[KENNETH BROWN]

Thanks Ken Brown

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