RaggedEdge

So then are the Imco SC gears any "better" than the Merc XR's?

Or are we talking the same chit in a different package?

fossil fuel

XZ gears have a much finer helical cut face. The setup needs to be perfect for long life. The XR is a straight cut similar to gears used in a tractor. They are much more forgiving on the setup.....

Philm

No, the SC gears are XR gears, just in an Imco SC case.

The SCX on the other hand uses totally new gears, much larger, that wont fit in an SC or XR case.

John the Drive Man

What I see in your pictures, is just the nature of the beast. It does happen, but I can say not very often, I've been building outdrives for 30 some years, And Bravos ever since they've been out. I have had very little trouble with XR gears. And I've done many of them on all sizes of boats from 700hp and down. And very very little failure. They are a fussy gear that needs to realy be set properly. There is no room for error. I've got large boats with 700 plus hp and getting 400 hours and better on them. A lot of my customers are Poker Run customers. So they run hard.

SDFever

Imco wanted to use a different gear but it's just not cost effective to find the source etc.

So they built a drive using the same gear that is still a little "better" than the XR depending on how you look at it.

There are NO cathodics so you're screwed in salt but the case is designed way better in my opinion. It moves a much higher volume of oil around. The cooling shower is built in and distributed nice and even. Finally, the case is thicker in areas and is built to lower the amount of tower flex and movement so everything is better "contained".

I've been to their facility a couple times and took some tours. It's a super nice product but mainly for fresh water use.

Philm

Doesnt happen that often? Seems like every drive guy I talk to, including Mr. Gadgets, says that the new XR gears are garbage, no matter how they are set up. The face hardness wears off when running any kind of power through them and once that happens, its into the soft metal. Game Over.

Here is my lower driven gear with 59 hours at 800hp and 25 hours at 750hp. Pushing a relatively light boat at around 4600lbs.

JaayTeee

I too have a growing collection of junk
XR gearsets, from my own boat and a friends.

I also originally thought that it was driver error or
set up issues also( before I had a boat with XR's) but it's
not.

Seems like it's a 50-50 chance on getting a good set.

I equate it to laying down sod over dirt that is
littered with junk.

It looks good initially, but pretty soon the uglyness
starts showing up

I've had them pit out ( like the pictures), crack and shear the cone off the gear, and the fun one, break a tooth off and junk out the case.

If and when the next set crap out, I'll probably switch
to X gears

A.O. Razor

..

SDFever

Well, after looking at your pic I'd say the mesh pattern in mine looks about like yours so maybe it isn't "that" deep..

Pretty unfortunate. Not available this week but I'm gonna start looking hard for the gears in other places.

Not holding my breath.

My hope is two fold:

1. That they can be found without Merc.

2. If they can, then hope that maybe Merc "told" the manufacturer to make them "cheaper" like the 525 cmi's and that perhaps a set off the shelf might just be better treated etc..

blue thunder

It is my thought that these low hr failures are due primarily to improper gear break-in. Mating surfaces of teeth are rough when new. High pressures on rough gear teeth during initial runn-in will cause loss of lube film and then galling of the teeth. A properly worn-in gear set will have smooth tooth contact areas and better lube film strength. This is prevelant in miter gears (XR) more so than spiral bevel gears (std bravo) because the tooth contact area is smaller on miter gears. Spiral gears have more of a sliding action and less "point loading".

BT