Broken 2.5L 1.87 box

[NZ Sidewinder]

Hi
Has anyone seen this before.
It's a broken dog pin from my 2.5L 225hp Merc circuit race boat.
The box started to lock up and the drive pulled off the course at which time it locked up proper.
When I pulled it down I found these two pieces of the pin and the single indent pin loose in the box.
The single spring was still on the dog.
The gears are history but there is no other damage in there.
The mesh on the gears was good.
Box is about a season old and spins at 6500rpm

[Jim Speros]

Every clutch dog I recall seeing had two detent pins and 2 springs wound in opposite directions. On my race 2.4 the pin was threaded into dog. I don't recall how HP 2.5 cases are.

Did your case survive? Often when gears fail it bulges the case adjacent to pinion.

[NZ Sidewinder]

Every clutch dog I recall seeing had two detent pins and 2 springs wound in opposite directions. On my race 2.4 the pin was threaded into dog. I don't recall how HP 2.5 cases are.

Did your case survive? Often when gears fail it bulges the case adjacent to pinion.

My big bearing case has double indents and double springs but the small bearing boxes have singles.
The case looks OK so far.
I'll use double springs next time.
May even use the big bearing dog with two indent pins.
However therefore plenty of small bearing boxes on the race course but most are doing 6000rpm.
The pin must have pushed the spring up out of the way and let the indent pin go as well.it
The driver said
The motor flicked down to 6k twice in a few seconds and he backed off immediately.
Coasted into the middle and switchd off.
Tried to start again in gear but was locked.

[25two.stroke]

That is a fishing propshaft in a race application...no good.

[25two.stroke]

You need to get a clutch dog with a threaded cross pin that also has the 2 detent pins mentioned above and two counter-wrapped springs with tanged ends that cannot spin and also hold the cross pin from un threading. You have the same kind of clutch that comes in fishing lower units and came in the first generation of CLE lowers. One cross pin that just slides in (no threads) and only one spring holding it in. They were known to fly out under stressful loads...that pin can squeeze past the spring.

[NZ Sidewinder]

These shafts are all we have for the 2.5L motors.
The fat shaft is generally used here on the 3.0L motors and maybe offshore race boats.
We do run caged needle rollers in the carrier though.
I wouldnt run an ET on these shafts as they snap but overall these shafts don't give us problems.
We don't run our circuit Vee bottoms past 7000rpm and tend to run them deep, no less than 2 1/2inch below pad.
Most boats in my class run basic props also, like trophy.
I run a 26p x15 Michigan wheel( ballistic) which arnt too agressive on the gearbox.
That said, I'm now going to sort this so it won't happen again

[25two.stroke]

You can put a threaded cross pin and clutch on that propshaft and your issue here will never happen again.

[NZ Sidewinder]

Easier said than done down here in New Zealand.
I have many boxes, gearsets and dogs etc but not a single threaded dog.

[David - WI]

Easier said than done down here in New Zealand.
I have many boxes, gearsets and dogs etc but not a single threaded dog.

Do you have a part number?

[NZ Sidewinder]

No I don't.
It's probably from a sporty.

[Jim Speros]

https://www.mercruiserparts.com/bam/.../30677/1505/23

2.4 offshore
line 61 and 62

Appear to be available

[donmac]

You need to get a clutch dog with a threaded cross pin that also has the 2 detent pins mentioned above and two counter-wrapped springs with tanged ends that cannot spin and also hold the cross pin from un threading. You have the same kind of clutch that comes in fishing lower units and came in the first generation of CLE lowers. One cross pin that just slides in (no threads) and only one spring holding it in. They were known to fly out under stressful loads...that pin can squeeze past the spring.

I've never seen a pin break or come out 2.4 offshore case in hundreds of hours rough offshore with 3 blade cleavers!I can see the pin breaking if shifting while running threaded or spring retained! I would think it's improper spring install!

[NZ Sidewinder]

I've found a big bearing box in my heap and raided it of parts.
Double indent dog, a pair of hooked springs, indent pins with holes in and the long spring loaded dog pin rod.
I've not been able to figure out why the big bearing boxes have that long dog pin rod with the spring in it, but it's in there now.
The hooked dog springs are wound so that the load drags on the hook rather than pushes.
I also clocked up 5 propshafts in order to get a really straight one.
I use the alpha carrier, they are NZ$230.00 which is US$115.00
This rebuild gets a new case and new gearset.
The 1.87 3 piece genuine gear set was NZ$570.00 which is US$285.00, included small forward bearing and internal forward bearing needle roller.

That was old stock I think.