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Honda BF9.9 Grinds until slowly engaging to full gear in forward

Randy S

New member
Reverse gear works fine been when put in forward a clacking sound continues for a minute or two then finally slams into gear solidly. It sounds awful until its all the way engaged. I confirmed its not a cable adjustment need. The shifter cable pushes the lever fully into forward position. So i opened up the lower end and removed the prop shaft expecting to find a worn clutch shifter. But it is not worn and neither is the hypoid gears or clutch dogs. I did however find a shredded thrust washer in front of the reverse gear. I believe this washer keeps the prop shaft fully forward so when the shifter is in forward gear the clutch shifter travels all the way forward towards the forward gear. I hope by just replacing this washer it will solve my problem but am not totally sure. It seems too simple for what it was doing. Im going to replace it and see what happens. Can anyone confirm this would cause my problem?
 
I'm not sure about the washer you're replacing. This transmission uses selective shims for adjusting gear lash.

What you describe sounds like a mis-adjusted shift shaft. The shaft is pulled UP from the gearcase to engage forward and pushed DOWN into the gearcase to engage reverse. Find the long shift shaft adjustment nut at the junction of the upper and lower shift shafts at the front of the extension case. You may find the jam nut loose.

The initial adjustment is done by shifting the transmission into reverse and backing the long nut UP onto the upper shift shaft. Then, reengage the threads on the lower shift shaft and turn the nut DOWN onto the lower shaft 3/16". Snug the jamb nut and test for proper gear engagement. You might have to make a minor adjustment from the initial setting to get it to shift like you want.

CAUTION: Whenever the transmission is shifted with the engine not running, you should be slowly turning the prop as you apply pressure to the shift shaft. This allows the clutch to engage and prevents binding and the possibility of bending the shaft or linkage.

I'm surprised that you say that you don't see any clutch dog wear. The dog "ears" bouncing against each other and not engaging are likely the source of the noise you were hearing. The clutch dogs need to have crisp, sharp, well defined edges to engage efficiently. If they are rounded even just a little you should replace them. They aren't very expensive and cannot be filed back into shape.

Also, with the engine running all shifts should be done with a swift, firm motion at idle speed to minimize the clutch dogs "bouncing" off each other and causing premature wear.

Let us know how you're doing after you replace the washer.
 
I'm not sure about the washer you're replacing. This transmission uses selective shims for adjusting gear lash.

What you describe sounds like a mis-adjusted shift shaft. The shaft is pulled UP from the gearcase to engage forward and pushed DOWN into the gearcase to engage reverse. Find the long shift shaft adjustment nut at the junction of the upper and lower shift shafts at the front of the extension case. You may find the jam nut loose.

The initial adjustment is done by shifting the transmission into reverse and backing the long nut UP onto the upper shift shaft. Then, reengage the threads on the lower shift shaft and turn the nut DOWN onto the lower shaft 3/16". Snug the jamb nut and test for proper gear engagement. You might have to make a minor adjustment from the initial setting to get it to shift like you want.

CAUTION: Whenever the transmission is shifted with the engine not running, you should be slowly turning the prop as you apply pressure to the shift shaft. This allows the clutch to engage and prevents binding and the possibility of bending the shaft or linkage.

I'm surprised that you say that you don't see any clutch dog wear. The dog "ears" bouncing against each other and not engaging are likely the source of the noise you were hearing. The clutch dogs need to have crisp, sharp, well defined edges to engage efficiently. If they are rounded even just a little you should replace them. They aren't very expensive and cannot be filed back into shape.

Also, with the engine running all shifts should be done with a swift, firm motion at idle speed to minimize the clutch dogs "bouncing" off each other and causing premature wear.

Let us know how you're doing after you replace the washer.

I paid close attention to the position of the vertical shift shaft. With the prop shaft out i could easily see where the nose of the shift pin rests. With the boat shifter on forward the vertical shifter rod is up exposing its tip which is the lowest point of the hump allowing the clutch shifter to engage the forward gear and clutch dogs. I have pictures of the clean mating surfaces if i can figure out how to post them on here.Image2714948876486242968.jpgImage3268265610984761292.jpg
 
I will show pics of the clutch shifter later. But it is just as clean as the dogs on the forward gear. I understand the clutch shifter is of a softer metal so that wear appears first on it rather than on the gears on the clutch dogs. Is this true?
 
I can't answer you about the hardness differences. I don't know. I'm not a gearbox guru by any means. I've just had a few of them apart and they seem simple and straightforward to repair. Although, the only one I encountered with mangled up parts, I replaced the whole assembly instead of trying to revive it.

I'm not sure about the pictures you posted. I couldn't enlarge them without them getting pixelated or "blurry". Is it my eyes or is the hypoid gear in the bottom photo torn up some?

It looks like teeth are chipped up pretty bad...??? If so, I'm not sure what to think other than something HARD must have been rattling around in there???
 
Replace the thrust washer.----Then I think you need to make sure that the shift rod is adjusted properly.----Easy to mess that up on a water pump repair job.----I say the shift rod is out of adjustment.----Year of this motor ?
 
This site only allows 97kb files to upload. I had to reduce the file size to allow them to be uploaded. However from my phone they look sharp as a tack. The images show they are pristine. Like new. No wear. No metal shavings. Hypoid gears are clean, dogs are crisp. There's still some gear oil on them that may look like they are sheared or worm but they are not.
 
Yes it is.-------You just need to work out how many turns of the barrel nut / engagement of the barrel nut / the lock nut ETC------This is all on the rod in front outside the lower unit
 
I found that area to access the adjuster nuts. Its a very small window in the outer housing. The adjustment was not necessary. The inner thrust washer i replaced solved the problem. After reinserting the shaft with new o ring and thrust washer I tested the engagement by hand. Then filled the case with gear oil and submerged the lower end in water. Fired up the engine and pushed throttle lever forward. The gear engaged solidly and under idle speed prop activated as designed. Went several times in forward and reverse with no slippage. I will comment back once I've tried it on open water. Thanks for all the suggestions. I learn a lot from every comment. This was my first time working on an outboard motor lower end but I am good with mechanical things. It was always a mystery to me how the power was transmitted to the prop from the engine. Now I know and its really not that complicated.
 
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