Mercruiser 470 Repower

Gentlemen
I realise Know I might have really put my foot into it, What I should of said is there a leg interchangeable with the R leg, maybe an alpha 1, at least now I know not to purchase a bravo if one comes up!
Now Please excuse my ignorance, I think this is why we have forums to ask the ask the questions, what is a cut out switch? I have had outboards all my life and I know to change from forward to reverse or neutral to a gear the motor has to be in idle, this is done through a simple mechanical
lever nothing special, I thought the leg would be the same deal.

 

No, all Mercruiser 1 drives, (alpha, R, MR, Gen I Gen II) need a cutout to drag them out of gear.
(All of these drives are basically interchangable but none are enough better to warrant doing that. Going to a Bravo is well worth it
If if you can get the idle low enough so there is very little load you might drag it out of gear but the shift components are not designed to do this.
OMC (looper) V6 and V8 outboards and late model sterndrives also had shift interupt switches.

 

Excuse my ignorance again, from what you are saying you cant change gear without killing the motor, this means to change forward to neutral or vice versa including reverse the motor has to be killed then restarted? I think I have read this wrong, if not that cant happen! I realise to change you have to be at idle but from what is being said this means you have to start in gear? What I was trying to say earlier is that there are mechanical units that will not allow you to change gear while any acceleration is on the motor.

 

Mercruiser uses clutches to change gear.

The clutch is held in position by the engine torque because the clutch angle is less than 90 degrees. To release it, the clutch cable it attached to a triangle on top of the engine that swivels around a pin and pushes the lever of a switch as soon as the force pulling or pushing the bowden cable exceeds a certain threshold.
The switch shortens the ignition for a fraction of a second thus removing the engine torque and releasing the clutch, that is all.

The same can be achieved with the fuel valve on a diesel engine.

 

Ok looks like I'm getting a bit of an education here, that's good! would the original 470 motor had this? or would it have been just a some sort of breaker in the ignition system. the reason i ask I still have all the parts from the 470 motor.
I don't really like the idea of a fuel tap or solenoid on the fuel line starving pumps of fuel on a diesel is not the best thing to do. This could be overcome by using the DID electronic system on the motor, rig up a switch that switches the injectors off for a second until the gear changes, sounds like it will work as the same as the old system.

 

Yes, the original motor had it also.
A mechanical injection pump has no other option than the shut-off fuel valve, engines with electronic MMU have other means to momentarily suppress injection.

 

Nani has a line of marine diesel engines based on the Toyota 4 cylinder. Perhaps a marine clutch in front of the outdrive. http://www.simplicity-marine.com/nanni.htm

 

Oh Crap some things just seem to get bigger than Ben Hurrs 21st, as soon as you think your on top, it all falls in a heap. Well there's another thought could I not just tap into the ignition from the key the ON/OFF button and use that with the original circuitry from the 470, sounds like an awful system switching motors on and off like that!

 

You cant drive the sterndrive backwards, i.e. with opposite input rotation

 

sounds good to me

 

Looks like we have the solution to that problem as well, who would be the best people to buy a rebuild kit from? I'm in Aus, or better to import from the US, unless someone can recommend an agent for parts?

 

The shift switch is just a micro switch that shorted the ignition to ground.
I'm sure you could get a switch to do what ever you want as long as you can get control of your injection pump.
Merc have a large network in Australia.

 

Yes thanks, I'm certain if I made some inquiries I can get what I need to make it all happen. I think now I should really start putting some hours into building the hull, one thing if you build a boat in Aus you need a ABP (Australian builders plate) to get the vessel registered, the only hassle is nobody knows anything about them. Dont you love our system!