Backlash measurement - Getting no lash.. measurement error or wrong shim?

[mrskipper]

Hi all,

I've never done a backlash measurement before so i thought to give it a go now while rebuilding a lower unit for a F15.
Looking at the service manual, i ..:
1. Removed the lower unit from the outboard
2. Removed the water pump assembly
3. Opened up the gearcase and pulled out the axle, leaving only the pinion gear and the forward gear inside

Now what i did is that i, from above the water pump assembly, pulled the axle rod up and tried to rotate it gently back and forth. At this point i understood i should get some play between the teeth of the gears, but i get absolutely no play at all. Every little movement, as delicate as it might be, results in the gears moving. I interpret that as that i have no backlash on the gear and that it's probably wrongly shimmed.


Now the question is... Did i do it the right way ? Would like to doublecheck before i start ordering the new parts

Thanks again!

 

[alldodge]

3. Opened up the gearcase and pulled out the axle, leaving only the pinion gear and the forward gear inside

Have not seen the manual, but most cases for measuring backlash, the prop shaft (axle) is installed and rolling torque is met. Then backlash is checked with pinion gear.

Example of the Bravo
The pinion depth is set. Then rolling torque is measured. If it passes rolling torque, then the prop shaft is installed and rolling torque measured. Shims are changed out to achieve result.

Now prop shaft and case are held tight and backlash is measured every 90 degrees on the pinion shaft.

If the prop shaft is not installed, then the gear is not held in position and moves around

 

[mrskipper]

Thanks @AllDodge! Although a little confused and lost now... I have been checking the manual also and you were right, it says to install the prop shaft back on.

But if i reinstall it, how should i do with the gear? Should it be engaged in forward or rear? and how can i check the backlash, i turn it around until it hits the gear - squarey/rectangular part or? I thought it was to turn around to feel the play between teeth but am not sure how to do it

 

[alldodge]

First and foremost I'm not a Yam guy

It has to be in gear otherwise the gears don't mesh and no lash can be measured. Your spec list forward lash and .007-.0034 lash

It also appears you need to install the puller so it will push the shaft in and torqued to 3.6 ft lb

All your info need appears to be in the pic you posted

 

[racerone]

????----Pinion and forward gear are always meshed whether in forward or neutral.----Gears do not move when shifting is done.

 

[alldodge]

????----Pinion and forward gear are always meshed whether in forward or neutral.----Gears do not move when shifting is done.

And your question is????

 

[racerone]

Sorry you say it needs to be in forward to mesh the gears.----And that is NOT a correct statement !!

 

[alldodge]

Sorry you say it needs to be in forward to mesh the gears.----And that is NOT a correct statement !!

Not in this thread, said in needs to be in gear (other words so prop shaft gears do not move)

Sorry, but again what is your question or at least a point?

 

[racerone]

Post #4 says it has to be in gear otherwise gears do not mesh.----That is a mistake as the pinion / forward / reverse gears are always meshed !

 

[alldodge]

Post #4 says it has to be in gear otherwise gears do not mesh.----That is a mistake as the pinion / forward / reverse gears are always meshed !

Yes I did say in gear, but not forward. The point has already been made and it appears your trying to make a grammar comment and not an actual issue to help or hurt the OP.

I may be wrong but maybe I have missed a critical issue so I will ask the mods to comment if they will
What say you Bondo , GA_Boater , Fun Times , achris , southkogs

 

[achris]

OK, not going to comment on who's right or wrong, I'm sure as gentlemen you'll settle this between yourselves in a manner becoming this forum.

On to the OP's question. Setting the backlash between any gears requires both those gears to be loaded, or 'load simulated'... That's what the puller is doing with the propshaft (never heard it called an axle, but that is also a discussion for another day).... The forward end of the propshaft has a shoulder which pushed on forward gear, and loads it into its bearing. Putting the box in 'forward gear', ie, sliding the shift dog into mesh helps the loaded propshaft to 'lock' the gear so the backlash can be measured. Holding the box downside up allows the weight of the drive shaft and pinion gear to put the pinion in the same position as it is when it's running....

Hope this helps,

Chris..........

 

[racerone]

Once backlash is established you will need to check for proper tooth contact too.-------Installing / shimming gears is not the same level of " know how " as installing sparkplugs !!

 

[mrskipper]

I will try that incoming week and let you guys know how it goes, thank you for now