Swap driveshafts or get extensions? Please Help.

[TrophyNace]

Rookie mistake. Have a 99 Force 120 and bought another 120 with a bad head to swap a bunch of new parts on mine. Started swapping the lower unit since I have a bent skeg and found out it was only a 20" shaft. Can I swap out driveshafts and gear linkage off my 25" to the 20" lower unit or is it easier to buy extensions? Any information would be greatly appreciated. Thank you.

 

[Frank Acampora]

You have a two piece drive shaft with a splined coupler. If the new lower unit is later than 1989, it will also have a two piece drive shaft. I believe you can swap the 25 inch drive shaft onto the new lower unit. I also believe that the shift linkage is the same length on all lower units. the extra length is built into the mid-leg. HOWEVER, The Mercury lower units have a different shift arrangement SO. any lower unit before (I think) 1994 will not bolt up to your engine.

 

[jerryjerry05]

The 95-98 drive shafts are 1 piece.
89/94 Forces were 2 piece.
You'll need special tools to shim the unit.
Just bend the skeg back to the original place.
Just don't hit it too hard.

 

[Frank Acampora]

Late at night and I forgot Mercury lower units have a one piece drive shaft. Chalk it up to "old timers disease" LOL

You don't really want to swap drive shafts because they require special tools for shimming and setting gear backlash. Get it wrong and the gears will self destruct. Service life will vary depending upon how far off you are.

No matter what you do now it will cost you money: You can take the lower units to a service shop to swap drive shafts--but that will cost over 100 bucks an hour. You can cut off the two skegs and have the good one welded back on but again a welder will charge you around 100 bucks.

If the bent skeg is not too bad, fun with it. If you try to straighten it most likely it will snap. The aluminum is cast and you only get one bend. If you heat it almost to the point of melting you will anneal it and then you can straighten it but you need an acetylene torch.

Simplest solution: Sell the good lower unit on ebay. you should be able to sell it for almost as much as you paid for the whole engine. Then look for another correct length lower unit.

 

[TrophyNace]

Guys thanks so much for your incite...your input on this forum has been invaluable for everyone.

I would consider putting my lower unit back on but unfortunately I cracked the anode housing when tapping my lower unit off. That stud was the only one corroded on. Took a lot of soaking and some heat to free it up. I have vacation coming soon so I may throw it back on and hope that doesn't ruin anything.

 

[TrophyNace]

Ok now my steering is stuck. Have no idea if removing the lower unit caused this or it froze up over the winter. Regardless it is stuck midway and has absolutely no play. Now what....? Luckily I have a spare bracket assembly if I need to swap...

 

[TrophyNace]

Backed off the steering nut all the way and twisted the cable and rod with pliers to free it up. Lubed it up with grease real good and we're back to normal.