three plugs in lower unit

[Karl Seibel]

have a mariner 115hp with the lower drain plug, upper plug that says vent, and a third plug about five inches away from the vent plug, same height. is this a top fill plug?

 

[GA_Boater]

Re: three plugs in lower unit

The lower plug is the drain/fill and the vent plug is just that, a vent for draining and filling. You fill from the the lower plug until it comes out the vent.

The third plug could be a flush port. Don't take it out until you get a manual.

 

[Chris1956]

Re: three plugs in lower unit

Drain plug is Stainless and under the bullet. Vent plug is stainless and is under the antiventilation plate. The older Mercs had a plastic flush plug which allowed you to use a garden hose and an adaptor to push water into the water pump cover, to flush the motor.

 

[Karl Seibel]

Re: three plugs in lower unit

ok thank you.....i will get a manual....but all three plugs are stainless. they all look exactly the same.

 

[carholme]

Re: three plugs in lower unit

The two upper plugs are the same and are Vent plugs.

1. With gear housing in normal running position, place a
clean pan under housing and remove two vent plugs
and one fill/drain plug (with gaskets).
50558

Gerry

 

[emckelvy]

Re: three plugs in lower unit

It would help to know the year of this motor. On older Inlines there is a plastic flushing plug. There is only 1 vent plug, and the drain plug, located on the Port side of the lower unit.

On later models, there are 2 vent plugs as described, and the drain plug, located on the Starboard side.

To refill, you must have both vent plugs removed. Then, as oil is added, it will eventually spill out the rear-most vent hole. Reinstall the rear-most vent plug and continue filling until oil spills out the forward-most vent hole; reinstall vent plug, remove oil source & reinstall drain plug.

If you don't remove that rear-most vent plug when filling, the gearcase won't be properly filled with oil.

I recently finished servicing a 2007 90hp 4-stroke and that's how it went.

Strange that Merc would bring out a design that flies in the face of standard convention (one vent, one drain), but I'm sure they had their reasons!

At any rate, the gearcase took the expected amount of oil.

I've made the mistake in the past and not removed that rear vent plug, then scratched my head later when I didn't get a lot of oil draining out of the lower unit. Nor did the lower unit take anywhere near the amount of oil I expected it should.

HTH...........ed

 

[BBQRealtor]

Re: three plugs in lower unit

It would help to know the year of this motor. On older Inlines there is a plastic flushing plug. There is only 1 vent plug, and the drain plug, located on the Port side of the lower unit.

On later models, there are 2 vent plugs as described, and the drain plug, located on the Starboard side.

To refill, you must have both vent plugs removed. Then, as oil is added, it will eventually spill out the rear-most vent hole. Reinstall the rear-most vent plug and continue filling until oil spills out the forward-most vent hole; reinstall vent plug, remove oil source & reinstall drain plug.

If you don't remove that rear-most vent plug when filling, the gearcase won't be properly filled with oil.

I recently finished servicing a 2007 90hp 4-stroke and that's how it went.

Strange that Merc would bring out a design that flies in the face of standard convention (one vent, one drain), but I'm sure they had their reasons!

At any rate, the gearcase took the expected amount of oil.

I've made the mistake in the past and not removed that rear vent plug, then scratched my head later when I didn't get a lot of oil draining out of the lower unit. Nor did the lower unit take anywhere near the amount of oil I expected it should.

HTH...........ed

It's a great idea. Without that extra "vent" hole you have to fill by pumping the oil on the bottom till it comes out the top then hurry and put the bottom screw in. But, by having the vent, you can replace the bottom hole after draining and fill from the top, other hole. Air comes out the vent as oil goes in so it fills all the way.

 

[racerone]

Always fill from the bottom !!-----------------