96 Force 120 ELPT Lower Unit ? Now W/ Pics

cowdogs

Cadet
Joined
Feb 19, 2009
Messages
6
I have a 96 Force 120 ELPT that has not been ran in 2 years, I thought I would fire it up to make ready for this season and after doing a visual and adding fuel I hooked up the ears, turned the motor over a few times with out the plug wires attached to make sure everything turned over fine. I attached the plug wires put the box in N 1/2 throttle and when the motor fired it red lined, and seamed like it dropped into gear as the prop shot out of the lower unit breaking the two bolts and chunks of what looks at one time they were gears. Do I need a new lower unit ? What would cause this ?

Thanks for any help,
Bill
Prescott, Az.
 
Last edited:

NYBo

Admiral
Joined
Oct 23, 2008
Messages
7,107
Re: 96 Force 120 ELPT Lower Unit ?

Re: 96 Force 120 ELPT Lower Unit ?

It sounds like your control box wasn't working right. But I can't understand the rest of the fiasco. Why would the prop, with inards, shoot off the back??
 

cowdogs

Cadet
Joined
Feb 19, 2009
Messages
6
Re: 96 Force 120 ELPT Lower Unit ?

Re: 96 Force 120 ELPT Lower Unit ?

I don't know, the trip before I had the water pump replaced and all worked fine, then it went into storage for 2 years ( indoor storage ). I just hope I can get buy with out getting a new lower unit.

Bill
Prescott, Az.
 

NYBo

Admiral
Joined
Oct 23, 2008
Messages
7,107
Re: 96 Force 120 ELPT Lower Unit ?

Re: 96 Force 120 ELPT Lower Unit ?

Is the case cracked? The gearset, at the least is going to need replacement, and possibly the propshaft. You might be better off getting an entire lower unit.
 

Frank Acampora

Supreme Mariner
Joined
Jan 19, 2007
Messages
12,004
Re: 96 Force 120 ELPT Lower Unit ?

Re: 96 Force 120 ELPT Lower Unit ?

It doesn't sound good. Can you post a pic or two?

I suspect that the rear gland which holds in the spool and gears may have broken due to whatever reason and the whole prop, shaft, spool, dog clutch, and reverse gear assembly came out. Like NYBo I suspect that the gearcase may be cracked.
 

cowdogs

Cadet
Joined
Feb 19, 2009
Messages
6
Re: 96 Force 120 ELPT Lower Unit ?

Re: 96 Force 120 ELPT Lower Unit ?

I will try to get a pic in the am. I am not sure what came out, from looking inside the gear case it would appear that every thing from the vertical shaft out to the rear came out, all I can say is I am lucky no one was standing behind it. With the c.b. in N if I turn the fly wheel the vertical shaft and the gear towards the front in the gear case turns, is this normal with it in N ?

Thanks,
Bill
Prescott, Az
 

Frank Acampora

Supreme Mariner
Joined
Jan 19, 2007
Messages
12,004
Re: 96 Force 120 ELPT Lower Unit ?

Re: 96 Force 120 ELPT Lower Unit ?

At all times, the pinion, forward gear and reverse gear are engaged and turning. Because of their location, the forward and reverse gears turn in opposite directions. A dog clutch between them, splined to the shaft, selects which gear will be turning it and thus which way the shaft and prop will turn.

If everything came out, you should be able to see the sliding dog clutch just forward of the reverse gear.
 

cowdogs

Cadet
Joined
Feb 19, 2009
Messages
6
Re: 96 Force 120 ELPT Lower Unit ?

Re: 96 Force 120 ELPT Lower Unit ?








Here are the Pics, sorry for the size this is my first time posting pictures.
 

HAV2FISH

Chief Petty Officer
Joined
Oct 24, 2008
Messages
519
Re: 96 Force 120 ELPT Lower Unit ? Now W/ Pics

I have an extra lower unit w/25in.shaft that will fit your 120. For a good price, If your intersted give me a PM.
 

Frank Acampora

Supreme Mariner
Joined
Jan 19, 2007
Messages
12,004
Re: 96 Force 120 ELPT Lower Unit ? Now W/ Pics

Your gears, from what I can see, appear to be OK. The rear gland was broken off at the mounting ears and you will definitely need a new or replacement one. The studs are bent and should be replaced too.

BUT: The question remains, WHY? ---It takes a considerable amount of force to break those ears. I would expect broken teeth on the reverse gear and pinion. UNLESS: If the engine was in reverse gear and something became lodged between the prop and gearcase. This would supply enough wedging force to pry out the rear gland, breaking the ears. If I were you, since the forward gear looks grungy anyway, remove the pinion and forward gear. Clean the whole gear pak well and inspect everything closely.

The pieces in the oil are drive dog clutches. I can not see enough of them to comment on their condition. But, there should be only one drive dog clutch which rides on the splined section of prop shaft. The number of pieces I see leads me to believe that the dog clutch was broken during the event. This prop is stainless, ie. strong, and I THINK I see one blade slightly bent near the root at the hub. The reinforces my theory of something wedged between the prop and gearcase. Because of the nature of the accident, you must also remove the prop shaft and check everywhere for cracks. Check the splines to see that they have not been deformed and double check for a crack where the pin passes through the slot in the shaft at the splines. You had better hope that the shaft is not broken or bent. Now, you must also check the splines on both ends of the drive shaft and again, you had better hope that the shaft is not damaged.

So, it looks like, at a minimum, you need a drive dog clutch (very expensive new) and a rear gland (probably not cheap either).
 

Frank Acampora

Supreme Mariner
Joined
Jan 19, 2007
Messages
12,004
Re: 96 Force 120 ELPT Lower Unit ? Now W/ Pics

Upon further thinking, It occurs to me that if that engine went into gear at a very high RPM, the dog clutch could have broken. If a piece of this wedged between the reverse gear and the pinion, the resulting force could easily blow out the whole propshaft assembly.

The only problem is that in that case, I would be looking for damaged or broken teeth on the pinion and reverse gear. I don't see any damage but, of course, in the photos, all the teeth of the gears are not visible.

So, you have a job ahead of you inspecting every drive component of that lower unit.
 

cowdogs

Cadet
Joined
Feb 19, 2009
Messages
6
Re: 96 Force 120 ELPT Lower Unit ? Now W/ Pics

Frank, Thank You for your help, the unit did go into gear at a high RPM, I had the dog ears on and started the motor with the N button in at 1/2 throttle, the motor fired and 1/2 a second later, BAM. I then shut it down. The pinion looks ok as well as the forward gear, the gear on the prop has a few teeth with burrs. I will tear it all down this weekend and let you know what I find. Any thoughts as to why it would jump into gear ? Would it be cheaper to replace from the pinion to the prop, or just buy a remaned lower unit ?

Thanks Again,
Bill
Prescott, Az.
 

Frank Acampora

Supreme Mariner
Joined
Jan 19, 2007
Messages
12,004
Re: 96 Force 120 ELPT Lower Unit ? Now W/ Pics

A remanufactured unit will cost around 1500 bucks. EACH gear will cost somewhere around 300, pinion slightly less, and the drive dog clutch is well over 100 as is the prop shaft. SO: depending upon the damage you find, it may pay to repair it or it may pay to try and find a used one for 3-500.

The shift linkage is mercury designed, diferent than earlier Force, and I can not even surmise a reason why it would jump into gear. But I'll bet it's a sound you will never forget.
 
Top