Mercruiser shifter kill switch

[Texasmark]

Visiting this site is a never ending time consuming (something for a retired guy to do when nothing else is on the agenda) learning experience that keeps the mind active. I hear that helps to ward off Alzheimers. Also when successful, you get the comfort of knowing you helped somebody enjoy their boat just a little bit more. Boating was paramount in my life from tyke to recently when it just lost it's glisten due to several things related to senior citizen status.

Latest case was the Mercruiser shifter kill switch. For anybody that may be interested in that, I am offering the posting: [h=1]HOW TO: How the Shift Interrupt system works[/h]
Posted Dec 26, 2008, 8:38 PM, From the hand of Mr. Don S, a 62,000+ past contributor to this site. If you don't want to dig through the internal archives, just Google the title. Makes for interesting reading.
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In attempting to participate in a current problem, two questions came to mind and I want to toss them out on the table for you Mercruiser knowledgeable folks:

1. Why does the clutch dog in the Alpha 1 (for a name) have an overrun clutch on F "and" R gears where the equal HP Mercury outboard has it only on F gear? Confusing to me as the task is apples and apples, same HP, same year models, same company, same thought process, same Brunswick corporate engineering management (I guess)??????

2. Why is it that you have to kill the engine momentarily to take the pressure off the dog so it can shift with the Mercruiser when you don't have to do that with the outboard?

Thanks somebody else might be interested in the answers.

Mark

 

[achris]

Simple answer to #1 is :noidea:
#2, undercut dog clutch. Reason for undercut dog clutch is torque. The high HP outboards don't prduce the same amount of torque as the inboards.

 

[Bondo]

Why does the clutch dog in the Alpha 1 (for a name) have an overrun clutch on F "and" R gears where the equal HP Mercury outboard has it only on F gear?

Ayuh,...... I Don't Know, Mark,..... I figured the outboard gears looked like the outdrive gears,....

Ain't had my fingers in an outboard lower unit in many years,....
Still can't get the prop off my little 7.5 hp tugboat motor, so I ain't dug into it either,...

As for question #2, I found myself askin' myself, Why outboards don't stumble comin' outa gear, like outdrives,..??
Didn't have the answer then, 'n ain't run across it til now, since,...??

 

[Texasmark]

Simple answer to #1 is :noidea:
#2, undercut dog clutch. Reason for undercut dog clutch is torque. The high HP outboards don't prduce the same amount of torque as the inboards.

Yeah makes sense and since the Alpha 1 could be hooked to a 110 I4 (like I had in the 1965 I restored in the mid 80's....before the advent of the Apha) to a 200ish V8 5 liter. Whereas the OBs are usually running a cu in/hp 2 stroker or the little cubed OHC 16 valve. I didn't have all that fancy sensing circuit and all and the leading edge of the dog face was rounded off by the PO with his sloppy shifting and lots of hours. Therefore, it'd jump out of gear regularly.

I said it a couple of times and will say it again, your Bertram is one badass big water boat, even if it is a 20 footer (I think I remembered the correct length). Gday mate.

 

[Texasmark]

Ayuh,...... I Don't Know, Mark,..... I figured the outboard gears looked like the outdrive gears,....

Ain't had my fingers in an outboard lower unit in many years,....
Still can't get the prop off my little 7.5 hp tugboat motor, so I ain't dug into it either,...

As for question #2, I found myself askin' myself, Why outboards don't stumble comin' outa gear, like outdrives,..??
Didn't have the answer then, 'n ain't run across it til now, since,...??

Sounds like we are both nearing the bottom of the other side of the mountain. But is surely was fun while it lasted.

 

[Fun Times]

Possibly Faztbullet might know the difference between the two lower gears.

 

[achris]

Possibly Faztbullet might know the difference between the two lower gears.

It's not the gears themselves, it's the shift dog. In the stern drive the dog position is completely controlled by the shift spool, whereas in outboards the position is controlled by a cam and spring. With the spring pushing the dog towards FORWARD, the cam pushing it towards REVERSE, when required. I believe the bigger 4 stroke outboard now have a shift interupt much like the stern drives.

Chris.....

 

[Faztbullet]

Its the shifting design(spool vs preloaded and desmtronic) and ramp design on dog/gears...

 

[Texasmark]

Ok you guys, you put us in our place. What does desmtronic mean and what is the "shift spoon and how is it controlled vs the dog in the OB. They obviously changed things up because my '65 110 had a cam controlled dog.

 

[Scott Danforth]

cant talk about bigger outboards, however the little cam on the ignition advance going in and out of neutral on my old 9.8 did in fact accomplish something similar to the momentary ignition kill on the I/O's

 

[achris]

Ok you guys, you put us in our place. What does desmtronic mean and what is the "shift spoon and how is it controlled vs the dog in the OB. They obviously changed things up because my '65 110 had a cam controlled dog.

Desmodronic is where a cam moves the mechanism (usually a valve) in both directions. Think Ducatti motorcycle engines.

Both stern drive (Alpha series) and outboards use a dog clutch to engage the gears, but it's all about how the dog clutch is moved. In the sterndrive the clutch is moved in either direction by the rotary action of a shift crank pushing or pulling; whereas in the outboard the clutch is moved in one directiion by the action of a cam, and in the other by a spring-loaded pin working against that cam. ie, as the cam moves, the spring causes the pin to follow the cam.

Hopefully the drawings below help clear it up.

Sterndrive shift crank and spool.



Outboard shift cam and sprung pin.



Chris..........

 

[Texasmark]

Nice job of explaining that, Mr. Administrator Sir; even if you do have a badass 20' Beautiful Bertram. Grin