1997 120 hp Lower Unit - no reverse under load

nnk_boater

Cadet
Joined
Sep 2, 2009
Messages
22
I can shift into reverse on the muffs, but not in the water. After eliminating the shift cable adjustments and failing to find a used lower unit locally in my price range, I decided to open it up and see what I could find. Here is what I found.

http://s27.photobucket.com/user/nnk_boater/library/1997 Mercury Force 120/Lower Unit

What I did not find was three cam follower metal balls, I only found two. I removed the hub by lifting it up and out so, nothing fell out. When I looked down inside, I saw only two balls sitting on the cam follower. The shift cam is broken and I need a new clutch. I was going to get a new reverse gear, but after seeing the price, I think I like the one I have.

Questions:
1. Do I have enough surface left on the reverse gear dogs to reuse it as is?
2. Is a broken shift cam a common failure? How do I prevent the new one from breaking?
The previous owner paid $125 for the dealer to "DIAGNOSE AND ADJUST SHIFT CABLE" just a month before I bought the boat. When I read this, I concluded that the lower unit must be in good working order, the dealer just adjusted it.

3. Any ideas as to why I only have two cam follower metal balls?

Last, do I have to find that Quicksilver 2-4-Cw/Teflon grease for when it comes time to put it back together?
 

SkiDad

Lieutenant Commander
Joined
Jul 18, 2010
Messages
1,518
Looks shot to me. It's cheaper to sell your lower for parts and pick up a complete lower unit.
 

jerryjerry05

Supreme Mariner
Joined
May 7, 2008
Messages
17,926
No on the grease.
Any thin grease that will dissolve quickly.
I use OMC needle bearing grease.
The edges could possibly be reworked.
Find a machine shop and show them what you need.
The missing ball is probably what caused the damage.
You sure it ain't stuck up in the shaft?
The balls (called a cam follower) is still available. 12239A 1 30-35$
The shift control cam is 850307 21-24$

Somebody probably worked on it and didn't see the 3rd ball hit the floor.
 

jerryjerry05

Supreme Mariner
Joined
May 7, 2008
Messages
17,926
That one in the pic might not work.
Look around.
Find one for a Force.
 
Last edited:

nnk_boater

Cadet
Joined
Sep 2, 2009
Messages
22
That one in the pic might not work.
Look around.
Find one for a Force.

blackd's eBay reference is a "6 jaw" and mine is a "3 jaw". To use the six jaw, I need to replace the shift shaft - $140 plus removal of the power head (more tools - lift ring, hoist, ... :grumpy:) . I know this because SEI sells a 3 year warranted model but it only comes in 6 jaw so, it is not plug and play. It would be about $1000 to go that route (and lots of hours of my labor). This is more than I want to invest plus, I would then have a Chinese lower unit and I'm not sure how long that would last. Mine is 17 years old and needs a new clutch and shift cam. Not bad. I've not needed any special tools so far and I don't foresee the need for any.

Also, "Unit
needs re-sealed." = $44 aftermarket, I know because I'm about to purchase one to reseal mine. My limit is $425, purchased locally. I established this based on the one I missed out on in August that was a 1.5 hour drive away and was listed for $500 on eBay and sold for $425. All parts to repair mine will be $185 - seal kit and Clutch Dog Cam Follower Kit http://www.ebay.com/itm/231041098774. Based on the packaging of the Cam Follower Kit, I'm assuming this is a common failure.

At least I know what I've got and I'd be willing to bet any used unit (not refurbished - those go for $1200 and up) on eBay will have a reverse gear in the same condition as mine. I think my reverse gear has enough face left on the dogs to work just fine, after all, I don't use reverse that much. Granted, the clutch and cam I'm planning to install are not OEM, but everything else will be. The forward gear looks like new. The three jaw reverse clutch is just a bad design and was upgraded to 6 jaw on later models (why not - six jaws forward, six jaws reverse!).

Thanks to all for your feedback.
 

blackd

Petty Officer 2nd Class
Joined
Sep 27, 2013
Messages
152
nnk-boater, sorry. I should have read closer, because I knew it took the 3 jaw. Keep looking. They are out there.
 
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