Gearcase Blueprinting

[Roflhat]

Wondering what folk do to their gearcase to improve performance?
Was thinking of stripping all the paint off as it's quite thick and putting on one thinner coat. It's used it salt water or else I'd polish it

Also balancing the gears, not sure how unbalanced they generally are but I would think there's some improvement to be had there
Anything else worth doing?

cheers

[Fastjeff57]

How about running automatic tranny fluid instead of thick grease or oil? Modern manual trannies use it to reduce friction and increase gas mileage.

Jeff

[Roflhat]

Hi Jeff, I'd heard of that being done, not tried it but I might try some back to back tests to see how it performs
cheers

[zul8tr]

What kind of gear case ? Paint remove and polish up aluminum, shave bullet diameter and true up the profile to match both sides, put a point on the bullet, put a crescent lead edge on front up-right above bullet. I would leave the gears alone probably in reasonable balance and put time and $$ elsewhere.

How high do you run the gear case?

[Roflhat]

Standard Yamaha 70ces gear case, can't change the shape of it by adding lwp or point etc. Was going to balance the gears and re shim the gearbox at the same time

[zul8tr]

I didn't suggest a LWP? As for re-shim are the gears not meshing correctly or improper gear lash? Can't you just profile the bullet and reduce the diameter a bit? Diameter effects drag, smaller frontal area is better.

[Roflhat]

I meant I can't add anything such as lwp or a bullet point.
The gearbox works fine but shimming it to reduce the tolerance can help reduce friction. There's regulations for the bullet and skeg thickness which I intend to take my gearbox to

[zul8tr]

Shimming the internals of the gear box if for correct gear lash for proper tooth contact. When set to proper tooth contact and lash that's it. More lash than spec just might damage the gears. Run thinner gear oil to reduce friction. I use a 75w 90 synthetic. Redline makes a low viscosity gear oil. Tranny oil suggested will work but can't say the gears will like.

[Roflhat]

Alright, I've never tried shimming the gearbox but heard you can shim it tighter to gain some rpm. Not sure if there's much to be gained by balancing the gears seen as the diameter is relatively small but any gain is of course welcome
Did you do any back to back tests with the different gear oils? I looked into it a while back and it looked like Amsoil 75w90 or Castrol hypoy 80w90 looked like decent canditates

[hydrospeed77]

Also curious to know what others use. I'm also looking for more protection than a basic oil.

[Ron Hill]

Alright, I've never tried shimming the gearbox but heard you can shim it tighter to gain some rpm. Not sure if there's much to be gained by balancing the gears seen as the diameter is relatively small but any gain is of course welcome
Did you do any back to back tests with the different gear oils? I looked into it a while back and it looked like Amsoil 75w90 or Castrol hypoy 80w90 looked like decent candidates

Shimming it looser, may increase your RPM til it blows up. Raise the motor 1" and get a new propeller. This will do more than all the blue printing a gearcase can ever gain. Get the gearcase out of the water. (Less drag)... Sharpen the skeg...

[fs5]

Hi mate you can get the gears lapped so they mesh together better . Haven’t heard about shimming tighter.
Haven’t tried tranny fluid in mine yet haven’t been brave enough. They reckon if you do you should change it after a couple hours. But they say it works.
Grinding reverse gear off helps , can also trim a bit off the bottom of your skeg. But it’s minimal gains.

[Roflhat]

I don't mean shimming it so the gears are too close together, just taking the tolerance closer to what it should be from factory.

Hey Jake, lapping looks like the way to go thanks mate. Did consider removing the reverse function but the rules say it has to be able to reverse.
cheers