1988 125hp Force lower unit woes

[Jiggz]

The perfect way to adjust the shift rod is with the upper shift rod. It's a little bit tight and it's located way below the lowest carb. There are two 1/2 nuts that you will need to adjust. When I was biasing my forward gear, I have to loosen the top nut and also the bottom nut to tighten things up. By doing this, when I shift forward, the shift rod actually do more downward travel (which is the forward motion for the shift rod). So in your case, you will need to move the bottom nut down first and then tighten it up with the top nut. This will result in the shift rod moving or biased more to move up which is the motion required to go in reverse. Here's a pic on what the adjustment looks like:

 

[Sandy-man]

Thanks, Jiggz, sounds and looks easy enough. It will be a while before I'm done putting everything back together because I haven't even ordered the LU seal kit yet, will do that Thurs morning. When I get it all done and able to put her in the water I will report back on how everything went. Then the next thing I will work on is the seemingly very rich running motor. Smokes like a stack for a few minutes while warming up with strong, rich like exhaust fumes, and always smells rich even after running for quite a while. When trolling the smell really gets to my wife so much so she doesn't want to troll at all, would rather drift fish. That's OK as long as there is enough wind to push us along fast enough for crawler harnesses.

I read on another thread on here about what can be done to combat this problem so I'll be referring to that thread for info when I'm ready to tackle it. But for now, I have a few beers to drink. Talk at ya later!

 

[jerryjerry05]

You posted pics of the R side of the dog.
How about the reverse 3 cogs on the gear?

I see one and it has a bit of wear, along with the wear on the dog and the linkage not
being set right?? might cause the jump.

The top of the shift rod adjustment Jiggz described.
99% of the time the regular adjustments should be enough.
But you might be one of the rare ones that need that procedure.
Adjust it the regular way first.
Or if you do the adjustment, remember the turns you move the nuts.

 

[Sandy-man]

All 3 cogs on the reverse gear have about the same amount of wear as the one you see in the pic. I could be wrong but I think if I can get the linkage set so the cogs make good solid contact the slipping problem will stop. Fingers crossed

 

[Sandy-man]

Well I think I may have found the real source of the reverse gear problem but I don't understand why it hasn't affected forward gear as well. After putting everything all back together I measured end float of the propeller shaft and it is .110, WOW, that is .100 over spec. How can this not affect forward gear as well? Is it because the force of the water pushing forward against the propeller is strong enough to hold it tight to the clutch whereas in reverse the water is pushing in the opposite direction effectively maintaining a full .110 gap?

2 of my 3 sons are machinists, I'm sure I can get 1 of them to make me a .100 shim. Is there a special material it should be made from? I out it back together with all new seals and o-rings. Taking it apart again will I need to replace them all again, hoping not.

I wish I would've checked the end float before taking it apart. I'm certain I didn't miss putting all shims back in the way it came apart. I have no leftover parts on the bench or floor in front of the bench.

 

[racerone]

Reverse gear operates with very little load and is used for short periods of time.----Not likely that you would find only damage on reverse gear teeth on any outboard.----So yes look at adjustment / linkage issues.-----That clutch dog will work fine if you have proper engagement of clutch and forward gear.

 

[Sandy-man]

But I will need to shim to get rid of most of the prop shaft end float, correct? Then my question is where to shim, thinking probably in front of forward gear where there already is a shim, just not nearly thick enough? What might cause such a huge amount of end float, is there something else I should be looking at?

 

[Jiggz]

Since it's back together have you tried adjusting the shift rod as discussed earlier? If the problem is not resolved after adjusting/biasing shift rod, here's what the maintenance manuals states:

 

[racerone]

I do not believe you should be putting a shim in front of the forward gear !!!---------That is not the way to do things.-----The position of gears is critical.----End float on propshaft is NOT critical.

 

[Sandy-man]

, I haven't yet made any adjustments to the shift rod, I was too alarmed by the amount of end float in the prop shaft. My first thought was "I must've missed something", but I looked my work bench and surrounding areas over real thoroughly to make sure I didn't miss anything.

Unfortunately, I have a very full day tomorrow so I won't be able to get back at it until Thursday morning. I will make adjustments to the shift rod then and report back.

I wonder why the service manual specifies .010 end float if that isn't important.
​​​​​ It's covered in fairly great detail on how to determine how thick of a shim will be needed to attain that spec, that's why I'm so keyed in on it. I want to get this right without spending all my months spending allowance.

 

[racerone]

There is a spacer on the propshaft.------That spacer does NOT go " in front of forward gear " as stated in post #27

 

[jerryjerry05]

Before you install any shims??
Reassemble and take it for a ride.
Get away from the crowd, then unhook the shift linkage at the motor.
Then manually shift into gear and see if that makes any difference?
Unhooking the linkage eliminnates any shift or linkage adjustments you might make.

If you install a .100 shim, you can destroy the forward gear.

 

[Sandy-man]

There is a spacer on the propshaft.------That spacer does NOT go " in front of forward gear " as stated in post #27

I guess I worded that wrong, in front of forward gear would imply I would put it between the bearing cup and the forward gear. That's not what I meant, I was meaning in the same spot there is already a .059" spacer. But I won't add any spacers until I've run out the linkage adjustments discussed earlier. If those adjustments don't fix the problem then I will try the spacer.

 

[Jiggz]

"I wonder why the service manual specifies .010 end float if that isn't important.
​​​​​ It's covered in fairly great detail on how to determine how thick of a shim will be needed to attain that spec, that's why I'm so keyed in on it. I want to get this right without spending all my months spending allowance."

Of course, the prop shaft end play is also important considering the drive pinion is fixed. Meaning if there's too much end play rev gear will not properly mesh. But based on your pics the rev gear has no indication of slipping off the pinion gear. Instead, it was the clutch dog not being fully inserted into the rev gear, I believe.

 

[Sandy-man]

The perfect way to adjust the shift rod is with the upper shift rod. It's a little bit tight and it's located way below the lowest carb. There are two 1/2 nuts that you will need to adjust. When I was biasing my forward gear, I have to loosen the top nut and also the bottom nut to tighten things up. By doing this, when I shift forward, the shift rod actually do more downward travel (which is the forward motion for the shift rod). So in your case, you will need to move the bottom nut down first and then tighten it up with the top nut. This will result in the shift rod moving or biased more to move up which is the motion required to go in reverse. Here's a pic on what the adjustment looks like:

OK, Jiggz, I'm about to get into this and make this adjustment. Given how much end float there is, the .110 measurement was taken with it in reverse, how much do you think I should turn those adjustment nuts? I realize you probably won't have an exact number but just a wild guess would work for me.

 

[racerone]

??----Excessive propshaft endfloat does not change the position of the forward and reverse gear.

 

[Sandy-man]

??----Excessive propshaft endfloat does not change the position of the forward and reverse gear.

You are absolutely right, for some silly reason I was picturing the clutch staying in position like the forward gear while the shaft floats in and out .110". Duh is all I could say when my simple mind realized that was wrong.

 

[Jiggz]

OK, Jiggz, I'm about to get into this and make this adjustment. Given how much end float there is, the .110 measurement was taken with it in reverse, how much do you think I should turn those adjustment nuts? I realize you probably won't have an exact number but just a wild guess would work for me.

Since the evidence points to a slipping clutch dog in reverse, do the following before adjusting.
-First disconnect the upper and lower shift rod (remove pin) and test the lower shift rod by shifting it up and down to make sure there is no binding in either direction. Do the same with the upper shift rod using the throttle control handle. If there is binding, you need to fix this first before continuing on. I have a recent personal experience with the shift rod seal rubber dismantling and creating a bind on the lower shift rod. The system still shifts into fwd and rev but there is a very slight delay and grinding noise before doing so.

If there's no binding, reconnect the shift rods and do the following:

1. In neutral, mark the lower shift rod using the hole as the reference point.
2. Do the same when in forward and also in reverse.
3. Analyze the distance between the three lines, neutral against fwd and neutral against rev. They don't have to be necessarily equal since it could have been biased before. However, you want to know where you are starting with your adjustment so you can always go back where you started. And at the same time give you an idea if the shift rod is actually "too biased" forward.

Now go to the upper shift rod adjustment. Remember you need to make the shift rod move up more (which is the reverse position) meaning you need to move the stop nuts down. Starting with the bottom nut, make two full turns and do the same with the top nut.

Now check again the lower shift rod to see how much you have moved the shift rod or if it even moved at all. Since it's slipping I'll start at least 1/8" adjustment. And then just go from there for refinement. Do a test, even on the driveway on muffs you can shift into gear (just make sure all is clear and do not rev). DO NOT TRY DOING THIS WITH THE LU UNDERWATER IN A TRASH CAN! Of course, this is a no load test and not totally accurate. The final test should be in the water both on fwd and rev.

Let us know of your test results.

 

[DunbarLtd]

The washer that sits on the inside face of the forward gear determines the end float play and is called a thrust washer. A collar on the propeller shaft pushes up against this thrust washer. Some may call it a "shim", but they are the same thing.

In the service manual it suggests an end float play between .005" - .020". In the manual it states to remove the shift yoke before measuring for end float. So the shift rod is not engaged with the prop shaft at all. But in order to do this you will have to remove the gear box cover for access to the shift yoke. Which isnt difficult but can be a pain to deal with as the shift yoke can easily fall off the end of the shaft when installing. Having it in gear may give you inaccurate end float measurements but dont quote me on that. I am just relaying the info in the manual.

Since the book calls for between .005" - .020" I think you may have to address it. Seems like .110" is excessive. Make sure the thrust washer is still on the forward gear and is not severely worn or the face of the forward gear it rides on is not worn.

The only "shim" BEHIND the forward gear is going to be behind the race for the forward gear roller bearing. Some have a shim there and some do not. Since you are not replacing the forward gear and its race I would not worry about this.

Double check that forward gear thrust washer and make sure its not damaged or missing. With that much play i bet the washer isnt even on there. You can find them on marineenginecom and look up your engine model number. They have varying thicknesses you can order. DO NOT put any ordinary washer in there. You will damage the gearbox in doing so. These shims ares specifically designed for this application.

 

[Sandy-man]

Since the evidence points to a slipping clutch dog in reverse, do the following before adjusting.
-First disconnect the upper and lower shift rod (remove pin) and test the lower shift rod by shifting it up and down to make sure there is no binding in either direction. Do the same with the upper shift rod using the throttle control handle. If there is binding, you need to fix this first before continuing on. I have a recent personal experience with the shift rod seal rubber dismantling and creating a bind on the lower shift rod. The system still shifts into fwd and rev but there is a very slight delay and grinding noise before doing so.

If there's no binding, reconnect the shift rods and do the following:

1. In neutral, mark the lower shift rod using the hole as the reference point.
2. Do the same when in forward and also in reverse.
3. Analyze the distance between the three lines, neutral against fwd and neutral against rev. They don't have to be necessarily equal since it could have been biased before. However, you want to know where you are starting with your adjustment so you can always go back where you started. And at the same time give you an idea if the shift rod is actually "too biased" forward.

Now go to the upper shift rod adjustment. Remember you need to make the shift rod move up more (which is the reverse position) meaning you need to move the stop nuts down. Starting with the bottom nut, make two full turns and do the same with the top nut.

Now check again the lower shift rod to see how much you have moved the shift rod or if it even moved at all. Since it's slipping I'll start at least 1/8" adjustment. And then just go from there for refinement. Do a test, even on the driveway on muffs you can shift into gear (just make sure all is clear and do not rev). DO NOT TRY DOING THIS WITH THE LU UNDERWATER IN A TRASH CAN! Of course, this is a no load test and not totally accurate. The final test should be in the water both on fwd and rev.

Let us know of your test results.

OK, I ended up just adjusting the stop nuts 1 full turn down thinking that would be between 1/16" & 1/8". Afraid of going too far and moving the problem to the forward gear. And you weren't kidding when you said it's tight in there to make any adjustments. I had to cut one of my 1/2" combination wrenches in half to make a super short wrench in order to do this. I will be doing a test run on the local inland lake, Devils Lake, Monday morning to see how she does. If it's still slipping I will adjust another full turn and keep doing this until the slipping stops. And of course I will let you all know how it all went. I will probably slip in a few drifts with a couple bottom bouncer and crawler harnesses while I'm at it. Sure been missing my walleye fishing on Lake Erie.