Delcoing a 3 cyl 2 stroke

[MOPAR]

I have a boat fitted with an old 70hp Mercury outboard, The CDI has packed up. I rang around for a quote on the replacment parts but because of the age of the motor no one has parts anymore So I thought why not delco it!

The motor spec's: 700cc 3 cylinder 2 stroke

Im after some suggestions for the best way to do it

I was thinking of doing the ignition conversion using crank angle sensor and star wheel of a v6, with the engine being half the number a cylinders but firing twice as often I figure this should work. Im not sure what to do about a coil pack / DIS.

Any suggestion's

[Holden202T]

i reckon you'd be better off trying to fit a 6 cylinder dizzy to it and grind off every second notch on the wheel ... v6's have a fairly complex crank angle setup.

if you use a reluctor type dizzy then you can use a camira coil and ignition module on it ....

question ... how many rpms is this thing going to spin to ?

[MOPAR]

At full noise it pulls around 7500rpm. Your suggestion sounds good however trying to mount a 6 cyl dizzy won't be an easy task, it would have to be driven of the fly wheel somehow and being 2 stroke would need to be geared 1:1, Belt drive maybe ??

[Dec_head]

Some of the old ones run points with an ignition box
anyway i thought i just might mention that their is a site that reproduces just cdi's somewhere on the net i have had similar problems in the past
And the price difference was something like $800 genuine $220 reproduction with more warranty
I have a mate that is an outboard mechanic he has a backyard full of them for spares what it the model serial number of your outboard.

[MOPAR]

Cant see the serial number without pulling half the motor apart but It's a 1976 70 hp blueband, no point's on this model it has the mercury thunderbolt ignition system. Where abouts your mechanic mate live? I would be very interested if he has got any spare's or even a complete parts motor.

[UCMatt]

I think I have a spare thunderbolt here that we were running on the last of the Holden engined V8 Supercars.
They were a great ignition!
Will have a dig and see what I can find.

Cheers,
Matt

[MOPAR]

Thanks Matt, but I think we are talking about different things here, I dont think you would be using a mercury outboard ignition system on a v8 supercar somehow !

[Dec_head]

I couldn't see a 70 hp 1976 model they seem to be 65 and 75 prior to 77 i found this if it helps http://www.outboardignition.com/mandmse ... l=27&val=9
My mate with outboard stuff is in sydney i will ask him next time i go over.

[UCMatt]

A lot of the V8 Supercars in the mid 90's used the Mercury Thunderbolt ignition systems. One of the best CDI units available at the time.
The attached file shows how they were used with a Motec (we used Autronic at the time) ECU.
I have a photo somewhere of one of our engines on the Dyno with the ignition in view.
This is the same ignition I have on my Blue Band 90HP Merc.

[MOPAR]

Sorry I doubted you Matt. Im curious to know how they were setup, did they use multiple switch boxs with a coil for each cylinder or a single switch box and coil through the distributor?