Newbie to force in need for some help ASAP!

[jacobpourciau]

Hey fellows, first off AWSOME SITE. I just bought a force 70hp and i was observing the lower unit and wondering what the top two screws were on the unit itself. I know one is the vent screw (the one to the left), then there is one directly to the right of it......What is the purpose of that screw? I took it out and it was identical to the vent screw it just did not have "vent" written by it.

I am about to cahnge my lower unit oil in my force and was wondering how yall preform this task??

*Manual on the way! But going boating this weekend and have to do this, any help would be appriociated!!!!

 

[Frank Acampora]

Re: Newbie to force in need for some help ASAP!

First, I will make the assumption that it is an earlier 90s Force with the Force lower unit, not Merc.

One screw on top is FILL. The same sized screw on top is VENT. Someplace on the bottom--usually in front of the skeg will be another screw for DRAIN.
The drain screw can be the same as fill and vent, or it may be a 1/8 NPT slotted plug or it may be a 1/4 to 3/8 set screw.

Damn near the center of the nose cone of the gearcase torpedo on the starboard side, will be a slotted screw head about 3/8 diameter, recessed into the case slightly. This screw holds the shift yoke in position and should not be confused with drain screws and should never be removed.

To change the lower unit oil, put the engine in a vertical position or as near to it as possible. Remove the FILL, VENT, and DRAIN screws and let old oil drain into a small pan or oil change pan. This may take a while if the engine has the small set screw for a drain and the oil is cold.

Replace the drain screw. If it looks like the FILL and VENT, be sure the gasket or seal is in place and tighten very firmly. If it is anything else, either coat with anti-seize or teflon pipe tape. Pump fresh oil in through the FILL hole until it comes out the VENT. let sit for approximately 1/2 hour to let all air rise. Then refill until oil again comes out the VENT hole. Replace all plugs tight, making sure the gaskets are in place, Gaskets may be re-used but they are only 50 cents each and if there is ANY doubt, replace them.

Use marine grade lower unit gear oil. It usually comes 85-95 weight. You can buy it in any auto store, Wal Mart, K mart etc. You will need about a quart--maybe a tad more--I pump mine from bulk so I don't pay attention. In a pinch, If you can not find marine grade, (Not very likely) regular automotive rear end oil will do BUT it does not have the corrosion inhibitor package that marine grade does.

If when draining, free water comes out of the gearcase or if the oil is milky in color, you have a leak in one of the seals. It would be good practice to check the whole lower unit to find the leak and fix it before refilling.

HINT: When changing lower unit oil, smell it. It has a very distinctive sulphur smell which you will never confuse with anything else. If at a later date you see some oil on the outside of the unit or dripped on the ground while the boat is parked on the trailer, smell it. That will tell you from where it came and if you have a developing problem with the lower unit. See: little things like that will alert you to needed maintenance and keep you from being stuck on the water.

A boat is very much like a woman: If you treat her with respect and are sensitive to her needs, she will keep you happy. Ignore her needs or treat her badly and ------

 

[Dave K.]

Re: Newbie to force in need for some help ASAP!

Hello Frank, Always good to read your posts - Thanks! I have a question that may help Both of us. At the end of last season, I noticed gear oil coming out of a casting hole. I researched on this site & another, & talked to a few techs...was told it was unburned gas/oil coming down the LU. Hopefully that's the case, but, could it be something else?? No funny smell & good clean oil came out (no water) I'm somewhat mechanical & have been able to do basic maintenance but not sure if I could handle new seals (maybe i could)??? Anyway, Could this be something other than unburned mixture? Thanks dave

 

[Frank Acampora]

Re: Newbie to force in need for some help ASAP!

Lower unit oil is an extreme pressure lubricant.To get this property, it has sulphur bearing compounds added. This gives it a very distinctive odor--Not bad, not disgusting, just different and distinctive. Hard to describe but way different than motor oil. Smell it once and you will never forget it.

So: if what it leaking or dripping out of the weep holes or exhaust of the lower unit does not smell like Lower unit oil it can not be anything else but unburned engine oil. The carbs spit back a little gas/loi and sometimes --especially with 4 cylinder engines--some of it drips into the lower pan and works its way down. Then, of course, some of the oil put into the engine will not burn and will just blow out the exhaust ports. again, this will go down to the snout and sometimes some will collect in the lower unit and drip out the weep holes. If the oil and gas recycling system on the bypass side of the engine has partially clogged screens or is not functioning properly, more oil will blow out with the exhaust. This will smell like gasoline or regular oil. --- oops! hit submit before I was finished---

There are only a couple of places where lower unit oil could leak and come out the weep holes. Under the water pump is a torpedo shaped plate held on by three short bolts in addition to the four water pump bolts. This plate has a drive shaft seal which can leak, an O ring which can leak, and another O ring in a groove in the front, which seals the top of the gearcase. Any of these seals are easy to replace without disassembling the gearcase.

The lower gearcase has a propshaft seal, a seal on the famous shift yoke screw, and seals under the fill/vent and possibly drain screws. Lower unit oil can leak out any of these, drain down the outside and drip on the ground. To change the prop shaft seal, you must pull the spool. A needle bearing and seal are on the outside portion of the spool. That's it. You do not need to disassemble the gearcase, but sometimes it can be difficult to pull the spool because of corrosion. Factory recommends pulling the spool and relubricating the O rings yearly if the engine is used in salt.