Gearcase Blueprinting

[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