Used Force 125 -- lower unit

[Frank Acampora]

Well, I decided to start performing annual maintenace on a Force 125 that I bought used and ran all last year. Didn't change the gear oil when I first bought it because the drain plug was stuck tight and I was too lazy to disassemble the unit to change it and the oil. Besides, I was in a hurry to get it on the water and the engine showed signs of being well maintained. Good Gamble! --I lost!

Upon dropping lower unit I discovered a broken bolt at the water pump. Drive shaft was stuck in the crank and lower unit was difficult to remove because the drive shaft was missing the steel collar and rubber crank seal.

Upon removing the water pump, the lower pump housing was filled with oil. Smelled it! lower gear oil! Crap! lower seal has failed and there's bound to be water in the gearcase. also noticed that the shift rod had numerous deep Dykes plier marks on it where it went through its seal.

Removed the anode (There's a fun trip -- corroded in screws, chewed up head slots, and an impact screwdriver for about an hour). Removed the four spool screws. About 3/4 pint of water drained out the screw holes.

Removed the spool-- it came out easy; surprising for a salt water engine --had been lubricated. Thank you, Neptune! Removed prop shaft and reverse gear. No rust on internals and no worn or chipped teeth. Whew! I caught it in time.

Next step: remove broken water pump bolt, remove stuck drain plug, and replace lower water pump seal. Replace shift rod, shift rod seal, and drive shaft collar and crank seal. Anti seize the drive shaft before re-installing.

If I had waited and run it this year, it would most certainly have failed expensively and according to Murphy's Law, far from port..

Goes to show you: Buy a used engine and do all the preventive maintenance BEFORE you use it. I was lucky this time. You may not be.

Strange thing: the lower gear oil itself did not show signs of water contamination. I guess it sat long enough for the water to settle out

 

[Matthew A.]

Re: Used Force 125 -- lower unit

Hi Frank,
I was going to put checking out the lower unit until a later time. However, after reading your post here taking care of it now sounds like the wise thing to do.

 

[Matthew A.]

Re: Used Force 125 -- lower unit

I removed the gear housing cover today and found a worn seal as well as a leaky o-ring that goes around the drive shaft opening on the housing cover. Luckily, it appears most of the water entering the gear housing was due to the bad o-ring and not so much the shaft seal. The top bearing doesn't appear to have suffered any damage. Despite using a blow torch on the cover itself and banging like hell with a hammer and chisel, I could not get the shaft seal to come loose out of the housing. I did manage to destroy the seal itself. But the outer ring of the seal refuses to budge. [hopefully, that seal has a stainless outer ring or I'll be purchasing a new housing cover] Oops! lol.
I also removed the anode which to my surprise was easy to do. I would have removed the spool as well except it would have taken the right puller to do so. Considering I have never taken apart a lower unit and the only manual I have is to go on is a Seloc, I decided that perhaps I should wait until I obtain a factory manual or at best one that's more specific then the Seloc manual is.

 

[Frank Acampora]

Re: Used Force 125 -- lower unit

Matt: You can easily make a spool puller with a piece of steel about 4 in. long and 3/8 to 1/2 in. thick--maybe about 2 in. wide.
Drill a 3/4 in hole in the center, and two 5/16 holes the width apart of the anode screws. Buy some 1/4 X20 threaded rod and cut two pieces to the proper length.
Place the plate over the prop shaft and screw in the threaded rods until they bottom in the anode screw holes. Thread washers and nuts on the plate end and alternately tighten until the spool comes free.

Behind the spool there are two half rings that hold in the reverse gear, bearing, and aluminum bearing support plate. Reach in with a fine tipped screwdriver to remove these rings from the circular groove in the gearcase and withdraw the prop shaft, reverse gear, bearing, dog clutch, and plate as a unit. This may take a bit of force since the plate is a snug fit in the gearcase. Be careful not to drop the shift yoke located on the internal end of the shaft.
Reverse gear rides on a thrust bearing and washer set into the face of the plate, and a needle bearing pressed into the plate. These are standard and can be purchased at a bearing supply house.
Forward gear cannot be removed unless the pinion is first removed. Pinion nut is 9/16 locking and factory recommends replacing it if removed. Pinion gear is on a taper and takes a little force to remove. Lower end of drive shaft rides in a needle bearing pressed into the gearcase.
Keep tract of the thrust washers in the center of the gears and reassemble in their proper places. They may be different thicknesses and set the shaft end play. Buy a new crush ring for the top bearing: This ring is compressed when you re-bolt the lower water pump plate on and keeps the bearing race down in its proper position. Don't lose the shims below this race. They set the proper gear mesh.
This crush ring is not too critical though: Because of the curve of the gear teeth, while running, the drive shaft and upper bearing tends to be pulled down anyway.
BTW : Upper drive shaft bearing is a special yet standard food equipment bearing--costs about 45-60 bucks. Merc dealers will only sell it to you as an assembly with the shaft--big bucks.

 

[Frank Acampora]

Re: Used Force 125 -- lower unit

Oh, I forgot: When you re-install the pinion, tighten it to the shaft to the torque specs, using the old nut. This is critical as it sets the pinion back to the original spot on the taper and maintains correct shim height. Then remove the old nut and torque the new one to specs.