1972 Mercury 402 leg oil level

[aceallenk]

Bought a old 402 and wondering which plug is the oil level for the leg, FLUSH or VENT. Going to drop the oil tonight and will fill tomorrow. I assume I fill from the FLUSH hole and the VENT is the oil level. I'm also thinking its going to be a slow process to fill, any tips out there?

 

[Alumarine]

Re: 1972 Mercury 402 leg oil level

Welcome.

The flush hole is for flushing with fresh water and has nothing to do with oil.

There is a drain plug on the front bottom of the bullet.
You fill from the drain plug until it comes out the vent.

 

[jomishx]

Re: 1972 Mercury 402 leg oil level

aceallenk, the top hole on the lower unit (aka gearcase or leg) is what some manuals refer to as the flushhole. This is the vent hole. The bottom is the drain. my Seloc manual states it this way. Be sure to pump the oil in from the bottom with the vent screw out. When it starts coming out the vent hole put that screw in then quickly put in the fill screw so you dont lose to much fluid. Hope this helps

 

[Moody Blue]

Re: 1972 Mercury 402 leg oil level

aceallenk, the top hole on the lower unit (aka gearcase or leg) is what some manuals refer to as the flushhole. This is the vent hole. The bottom is the drain. my Seloc manual states it this way.

Sorry, but that's not right. The flush port is the flush port. It is not the vent. The flush hole is in no way connected to the gearcase. The flush hole is an access point to the cooling system so that you can flush it with fresh water if you run the motor in salt water.

There are two ports in the gearcase. The fill/drain port located at the very bottom of the gearcase, and the vent port located at the top of the gearcase. As mentioned, you fill from the bottom so that displaced air can escape out of the vent hole at the top. WIth the engine positioned vertically, fill the gearcase until the oil spills out of the vent hole.