Force 125 Transmission Clutch or Dog?

[JaxBoat]

Hello...
We broke it,
But we're just not sure what we broke.

1989 Force 125.....surprisingly reliable.

We were in fairly shallow water so the engine was just above idle when...... CLUNK!!!! sudden engine stoppage...not good. So I attempted to restart the engine....it started but as soon as I tried to put it in gear .....CLUNK.....ENGINE STOPPAGE......
So I tried this 5 or so times. And then I decided to pull off the engine cover and I held the idle a little higher while my wife put it in gear..... CLUNK.... ENGINE STOPPAGE......

So then I'm thinking....."Is the prop locked up?" I raise the tilt to find one of our ropes wrapped around the prop. I climbed out onto the engine and unwrapped the rope.... and good to go...... I think but then I realize that although I can move I have very little thrust or speed and I can feel an evile intermittent clunking.

So what do we think?

Stainless Steel prop feels tight. Out of the water I put it in gear and tried to turn the prop. Couldn't do it. Is there a rubber slipping sleeve between the prop and it's mounting shaft? Can It be tightened/repaired? adjusted?
Reverse felt better but I didn't try too hard to break more of my bottom end.

Or
What about a
Clutch Dog? Or Shear Pin? or..........?

I am somewhat mechanically inclined and it is time to do a water pump so I'm gonna be there anyway....... But damn................A perfectly good running piece of junk and I went and broke it.............

 

[Frank Acampora]

Re: Force 125 Transmission Clutch or Dog?

Did you pull the prop? Sometimes (it is difficult but not impossible with that prop) the rope can get behind the hub and wedge between the prop hub and the anode. That will put a quite nice resistance on the prop and may also cause the drive dogs to disengage and reengage with a clunk.

 

[JaxBoat]

Re: Force 125 Transmission Clutch or Dog?

I got ALL of the rope out right away and none got in behind the prop. But there is the clunking.
Did you say that removing the prop is difficult? What is a typical technique?

What/how/why would the dogs disengage and then re-engage?

Is this adjustable? Shift linkage?

I "think" that the engine and drive were fine before the rope boo-boo.

I'm thinking that I should do a bottom end tear down just to be safe. I have a decent set of tools and I have done car clutches and head gaskets (experience).

Will I need a special job specific tools?

 

[Frank Acampora]

Re: Force 125 Transmission Clutch or Dog?

Pulling the prop is easy. All you do is remove the prop nut and washer, then pull the prop straight off the shaft. Do this over land as sometimes the thrust washer will stick in the prop hub as you pull it off, then drop out (into the water and lost). You can not run the engine without damaging the lower unit casting without this thrust washer, so then you would be stuck.

Inside the lower unit (although it is sometimes called a clutch) is a dog clutch. This is not the same as a clutch on a car although it does much the same thing.

Foward and reverse gears are constantly in mesh with the pinion gear and are constantly turning when the engine is running (in any gear or neutral)

Each drive gear has three "dogs" on the face inside the gear teeth ring. The dog clutch has three dogs on each face of it. Sliding it forward engages its dogs with the dogs on the forward gear and the propshaft which is splined to the dog clutch turns the prop in a clockwise direction. Sliding it rearward does the same thing and turns the prop counterclockwise.

The dogs have 90 degree faces only about 1/4 inch high and engage much like you would entwine your fingers. If the dogs are not fully engaged, it is relatively easy for them to slip and disengage. If the 90 degree faces are worn rounded on the edges, they will slip under load also. If this happens at high speed, the engine will sound like it is banging or clunking loudly as it slips out of and into gear repeatedly and the boat will feel like it is lurching.

AND--- because drive dogs engage the gears, you do NOT try to ease them into gear as you would slip a clutch. The proper way is to quickly "snap" the control handle forward about 1/3 of its travel or until you hear the gears engage then continue the push forward to speed up the engine. It is normal to hear a mild "clunk" as the dogs engage and slam together.

You may have had drive dogs starting to wear and the rope accident just exaggerated it and brought it to your attention. OR more likely, the linkage is out of adjustment and there is not enough engagement of the drive dogs. The rope accident caused them to slightly wear the top edges and now they slip.

SO, the first thing to do is to check the throw of the shift linkage. On the midleg, below the engine swivel, you will see a stainless rod 1/4 inch in diameter. It exits the leg and is attached by a cotter to a larger cylindical piece at 90 degrees to it. Take a fine magic marker and mark the 1/4 inch rod where it exits the leg in neutral. Then put it in forward and mark it. Last, put it in reverse and mark it. The marks should be evenly spaced. If they are not equal, then the linkage must be adjusted. If you can feel the drive dogs slide over one another when you turn the prop in the correct direction, then there is not enough throw in that gear.

For example: If you put the engine in forward gear, then turn the prop clockwise, you will be attempting to engage the back faces of the drive dogs. Since the tops of the dogs are tapered to aid in smooth engagement, if there is not enough throw, they will slide over each other then drop together.

Since forward gear is engaged by downward movement of the shift linkage, if you do not have enough throw in forward, you must lengthen the rods. To do this, remove the engine hood. Centered under the bottom carb you will see a rod locked to the shift lever by two locknuts. To increase forward engagement, loosen the top nut about a half turn at a time and tighten the bottom this pushes the rod down slightly. Do this until forward engages properly. Don't go too far or reverse will be affected and you will also be putting excess pressure on internal yokes inside the lower unit. Too far, and the engine may also not go back into neutral.

Finally, if the linkage is properly set and you still have problems, then the drive dogs are worn too far. Since the dog clutch is usually a little softer than the gears, it can be replaced--but it is expensive. You can buy a used lower unit for not much more than a new dog clutch. I like to use a Dremel to reface all the dogs by hand. If you know someone with an end mill or if you have access to one--even better

If you have done automotive work, with a Clymers manual or factory manual disassembling and repairing the lower unit won't be difficut at all.

 

[JaxBoat]

Re: Force 125 Transmission Clutch or Dog?

Thank you very much for the response.

Number ONE.....ALWAYS START WITH THE EASY STUFF. So,I agree that doing the linkage adjustment is an appropriate first choice.

I understand the Dog Engagement, the relationship to linkage and adjustment and how new additional wear could now be resulting in the dogs popping in and out of engagement. (I had a Datsun years ago which had a 2nd gear that would pop out. The gears was worn/the teeth were very slightly rounded. But that "Taper" was enough to allow/induce the 2nd gear set to slide out.

Although I agree that testing and possible adjusting the linkage could be a good 1st simple step, unless the process reveals an obvious out of adjusted linkage and/or an "in the water and under load run-up" doesn't show a positive result, I think that I should also prepare for a bottom end disassembly and inspection. Will I need anything more that a standard wheel puller or slide hammer (and a good set of mechanics tools) to get the bottom end apart and back together ?

As I have owned the boat for a whole season and I have not yet done the water pump impeller I plan on working on the bottom end anyway......

Again, Thanks for the input.