Racheting/ non racheting gears and dogs.

[NZ Sidewinder]

I have here a merc 1.87 gearset sold and packaged as non racheting.
Also have a big bearing racheting forward gear as a comparison.
The non racheting gear has semi ramps.
The racheting gear has full ramps.
I've also got a full ramp dog from a big bearing case.
I while back I asked the question as to whether the so call non racheting gear could be used with the racheting dog.
Answer came back, NO.
However I've been taking a close look at these items and am now scratching my head.
It plain to see from the wear marks on the racheting gear that the ramped dog and the ramped gear (both racheting) only make contact on a small part of the ramp and not on the extended part of the ramp that forms the difference between the two types of forward gear.
In other words, the difference between a racheting gear and a non racheting forward gear is an extention to the ramp that doesn't get used at all.
To two types of gear are from a working point of view, identical.
In the photo the vernier is pointing to the wear marks on the racheting gear and that same short portion of ramp is included on the non racheting gear.

So what's up here?
Did Merc just make all gears ramped but label them differently.

[David - WI]

I didn't think ratcheting gears actually "ratchet" very often... only if you completely step off the throttle at high speed or the engine locks up??

[25two.stroke]

Wear under load vs free wheeling is very different. The wear you see is from shifting while running the engine. As the spinning gear flies by the stationary propshaft and clutch its likely to bump the clutch for a revolution before the clutch engages all the way and spins up. Thats the thump/clunk/skip going into gear. Thats what wears on the face of those ramps. The non ratcheting does the same thing.

I believe the full ratcheting on freewheel that you get with the gear on the right and the ramped clutch dog DOES engage the entire ramp on the gear. Cause the clutch should be fully seated up in that gear when it's engaged. So the clutch needs to have a full ramp to get it jumping up and ratcheting.

Set a free clutch (not on a shaft) on the gear and see if you can spin it by hand and simulate the ratchet.

[OnPad]

I didn't think ratcheting gears actually "ratchet" very often... only if you completely step off the throttle at high speed or the engine locks up??

I think it's kinda hard to hear happen at speed, or with the engine running, but my case's do it audibly everytime I shut the engine off in gear.

[NZ Sidewinder]

You are doing over 80mph toward a turning buoy.
30 yards from the buoy you button off causing the dog to disengage and howl as it rachets.
The ramps on the dog are slamming into the ramps on the
forward gear as the propeller continues to drive the propshaft at high rpm.
This leaves witness on the gear ramps.
Fact is that the full length ramps of the racheting gear show exactly the same wear pattern as the semi ramps of the non racheting gear.
I've examined it every which way possible and it's clear that under no circumstances do the full length ramps of a racheting dog make contact with the lower half of the racheting forward gear ramps.
In fact the first half of the ramp on a racheting forward gear isn't even machined, it formed in raw forge
So on this basis, the question remains, why can't a non racheting forward gear be used with a racheting dog?

[OnPad]

Give it a shot, maybe you'll teach us something. Should be easy to mock up if you have a pile of parts from each.

I have half a dozen that ratchet, and one new case that doesn't. That lone duck would get a ratcheting dog if you tell me it works.

You made me do a little homework in the service manual. From looking at the pics your theory makes sense..Did a browser search, and found where a few people were talking about doing this mod with 3L cases, but I didn't read long enough to find someone that said anything about the smaller cases.

Your racing sounds exciting!! Even more so with a non ratchet case. On the other hand, it would have a brake effect.

[LakeFever]

I have a few mint non ratchet cases and only two ratchets, one is meh. I would love to use the gears from a non ratchet in my new build so yes please try and let us know. S&F is awesome thanks for this thread

[OnPad]

I have a few mint non ratchet cases and only two ratchets, one is meh. I would love to use the gears from a non ratchet in my new build so yes please try and let us know. S&F is awesome thanks for this thread

I think you would need whatever gears came in the case, as the front bearing is different. The only thing that would have to be changed is the shift dog,.....maybe.
No expert here.

[donmac]

the spacing of the gear driving surface needs to match the clutch dog boss spacing or you'll be driving the gear and shaft from one flat! I can't see that being good for longevity! I would check that the gear is being driven by all the dogs boss's

[NZ Sidewinder]

I don't want to run non racheting, too dangerous in a motor lock up.
This thread is asking the question, why can't I just swap out the forward racheting forward gear and dig.
The shift rod for the dog pin from the racheting case needs to stay with the dog as well so that dog can move.
Our circuit racing is great fun.
Generally 1/2 mile straights and 1/8 mile turns.
Sometimes 2 buoy turns and some time 4 buoy long sweepers.
My class tops out at about 82mph.
2.5 Merc is the engine of choice as the 3.0L don't get through the turns as well as thlighter 2.5
Here is a video from one of my boats.
19ft 6 Cyclone.
NZ made hull 30 yrs old now
Mildly worked 2.5, probably 225-230hp

https://youtu.be/PkXBLwnxws8?si=IxDWJ2b41WDlDn48
There's about 8 boats in this race

[NZ Sidewinder]

This is what's going g in the case and I reckon it will be fine.
Small bearing gearset labeled from new as non racheting.
This set didn't include a dog.
A pair of hooked springs from a big bearing case
Dog pin shifter rod from big bearing case.
These ones are single compression spring type noy double like a sporty.
Racheting dog from the big bearing case
Caged neddle roller bearing in the carrier and seal retainer.
This carrier has 2 propshaft seals but I've squeezed 3 in before, hence the retainer.
Alpha carrier, ( wide boss)
Pinion height exactly .025
Backlash .022

[OnPad]

I think that will work fine.

From what I understand swapping a big bearing front gear that has the ratchet ramps with a small bearing non ratchet forward gear is not a option. Because the bearing races dont fit the gear or the case, or something to that effect. Like I said no expert on this stuff. Alot of the other parts are interchangeable from what I read.

Big bearing ratcheting parts from the early eighties.
A post from someone that has some experience.

[NZ Sidewinder]

Correct
A big bearing forward gear and bearing will not fit in a small bearing case.
The job of trying to do that would noy get very far.
This job is about using small bearing gears in a small bearing case but using big bearing case acheting Dog and accessories on a non racheting small bearing forward gear.
The box is already assembled.

[OnPad]

Did merc make a ratcheting small bearing front gear?

[NZ Sidewinder]

Yes I've got one in front of me here.
Issue is that I have lots of non racheting as well and a new set that's non racheting.
The goalof this thread is to establish whether those non racheting gears go in boxes or in the trash.
Right now I'm I inclined based on measuring and fitting to say there is no effective difference between the two types when used with a full ramped dog and accessories.
Therefore the non racheting gear I have won't be going in the trash