Low unit oil change question for 90 HP Force

[heatro]

None of the other posts have mentioned this issue. I have a 1997 Force 90HP and went to change the lower unit oil and noticed there are 3 plugs instead of 2. I've attached a picture for reference. The lower plug is not in question, but at the top of the unit there is a plug labeled "vent" and a plug labeled "oil level". Should I remove both the "vent" and "oil level" plugs prior to changing the oil. It seems like it would be difficult to refill the oil with two plugs out at the top. Your feedback is much appreciated.

 

[Frank Acampora]

Re: Low unit oil change question for 90 HP Force

You drain the oil with the engine vertical. You replace the bottom plug. You then fill through the oil level plug with the vent open until oil comes out the vent. Let stand for 15 minutes to a half hour to let air bubbles rise then top off again until oil comes out the vent. Insert and tighten both top plugs.

 

[roscoe]

Re: Low unit oil change question for 90 HP Force

You should fill from the bottom on those newer Mercury gearcases.

Both top holes are used as vents, they are just at different levels.

Fill from the bottom till it comes out the "oil level" hole.

 

[jerryjerry05]

Re: Low unit oil change question for 90 HP Force

I drain from the bottom.
Then fill from the fill till it comes out the vent.
Then I fill from the vent till it comes out the fill.
Then again from the fill.
I HATE the idea of not enough oil!!!!!!

I like the idea of filling from the bottom till it comes out both top screws!!

 

[TwoFish]

Re: Low unit oil change question for 90 HP Force

I have a 1998 75 which has a similar setup. The two top holes are at the same height rather than staggered.

I fill from the bottom using a pump with a one way valve until oil comes out one of the top holes. Then let it sit for about half an hour to let any air trapped on the oil work its way out. I then trim the motor slightly out to make one of the vent hole higher than the other. I figure if I close the highest screw off last I have all the air out of the system. After locking off the top screw I remove the pump and fit the bottom screw. I always loose a couple of drops oil trying to fit the bottom screw.

The manual I have says to fill from the bottom of the gearbox but maybe filling from the top would prevent the loss I get removing the pump. The gearbox in the manual only has one top hole. Don?t know why they changed to two. Possibly to make it easier to fill using one of the top holes to fill through and the other as a vent? The other reason I can think of is the design of the top section of the gearbox traps air and needs two vent hole to purge it properly.

I?d be interested in people?s opinions on this as I have to change the oil again in a couple of weeks.


Always replace the washers on the screws. There cheap insurance.

 

[heatro]

Re: Low unit oil change question for 90 HP Force

Thanks for the input. I feel better now about doing this myself for the first time.

 

[Jiggz]

Re: Low unit oil change question for 90 HP Force

Isn't it amazing how complicated the English language is? Four responses to a single question and you basically got 3 different answers. When the labels on each plug clearly says what each function is.

 

[roscoe]

Re: Low unit oil change question for 90 HP Force

Well, my answer came directly from my factory manual, and I double checked because it is different for the older 85/125 hp motors with the dual exhaust lower units.

 

[Delta22710]

Re: Low unit oil change question for 90 HP Force

Unscrew the bottom screw on the unit. The oil will drain slowly. While it is draining loosen or remove both screws. The oil will drain out at the bottom faster. Once all the oil is out, pump oil through the bottom screw on the unit until it spurts out one of the (2) tops. Once this happens, replace the bottom screw on the bottom of the unit, and then replace both screws on the top of the unit. Tighten all screws. Easy Peezy Japaneezy !!! New oil

 

[Jiggz]

Re: Low unit oil change question for 90 HP Force

Unscrew the bottom screw on the unit. The oil will drain slowly. While it is draining loosen or remove both screws. The oil will drain out at the bottom faster. Once all the oil is out, pump oil through the bottom screw on the unit until it spurts out one of the (2) tops. Once this happens, replace the bottom screw on the bottom of the unit, and then replace both screws on the top of the unit. Tighten all screws. Easy Peezy Japaneezy !!! New oil

And you're the same guy who ran his 2-cycle motor with straight gas without any oil mix, right? Easy Peezy I guess!

 

[Delta22710]

Re: Low unit oil change question for 90 HP Force

Jiggz, did I say something wrong in my post? Oh, you must be an Admiral or something. God Bless.