Alternative CDI?

[pastorbud]

Has anybody been able to do what this guy seems to be working on?

https://www.iboats.com/ideabook/converting-1987-force-125-prestolite-ignition

 

[pnwboat]

I've received a few inquires from folks on the forum here but I'm not sure anyone else has done it. It's been working great since the conversion ( I think 3 or 4 years ago???). Biggest problem was determining which flywheel to use. The motors that use the CDM ignition have a crankshaft that is larger in diameter than the earlier motors so the CDM flywheeel (1995 and later) won't fit. The hole in the center of the flywheel on the later models is larger than the one for the earlier models. I found what I believe was a 1991 - 1994 flywheel for the SwitchBox ignition system that worked. It has the six separate magnets like the later model CDM ignitions and fits the earlier Force crankshaft.

 

[pastorbud]

Wow!

 

[roscoe]

1995 flywheel should work, CDM ignition started in '96.

Measure first to be sure.

 

[pastorbud]

I'm not ready to do it, just wondered if it was possible!

 

[brokenwrist]

I saw a video on youtube, where a guy removed the old chrysler cdi from the housing, and installed all the internals from an msd box. Of course he had a 2 stroke 4 cylinder, so he just left it set as an 8 cylinder engine. It was kind of cool to see, but he never said which wires would go where, as obviously the wire colors will be different.

 

[pnwboat]

Here are some pictures of the different flywheels.

Original Prestolite Ignition system flywheel.


What I believe is a 1991 - 1994/1995ish SwitchBox ignition flywheel. This is the one I used.


Later model 1995/1996ish - 1998/1999 CDM ignition system flywheel. Crankshaft snout hole is larger in diameter and will not fit 1994/1995 and earlier cranks. Notice the internally threaded lip for a flywheel puller around the center hole.


Here are the major components that you need to complete the conversion.

1. CDM coils/with mounting plate and wiring harness.
2. Flywheel
3. CDM ignition trigger assy..
4. Trigger assy. mount which also has the upper crankshaft seal. Bolt pattern to mount to the block is the same as the earlier Prestolite trigger assy. mount.
5. Stator assy. from 1995/1996 and later motor. Make sure the stator wires have the Green/White and White/Green wires. Should also have the two Yellow wires that go to the Regulator/Rectifier assy.


The only other problem that I encountered was the block attachment points for the coil mounting plate. One or two of the mounting holes in the plate did not match up to bolt holes in the block. Had to fabricate a bracket or two to make it work.

 

[NoFearForce]

You guys are awesome. I have found everything except the stator mount plate which I can't even find a part number for and also the flywheel. Which I will find a flywheel soon since I see the difference in the lip. Almost pulled the trigger on the wrong flywheel. :facepalm: Thank you so much pnwboat for this write up and break down of all the parts. Helps tremendously! If any one knows a part number for the stator plate please let me know.

 

[pastorbud]

Really helps to hear from the gusy who have been there and done that!

 

[NoFearForce]

Flywheel part #859241T10

 

[pnwboat]

Stator/Trigger mount part number is 819312A 1. Ebay has them used from $8 - $30. Probably wouldn't hurt to replace the upper crankshaft seal too P/N 26-828627. About $10 new. NOTE: The same seal is used on the lower crankshaft bearing.

 

[NoFearForce]

Pnwboat, you are a good send! Bought those two. Now to find a flywheel that's not $500.

 

[NoFearForce]

What I have for parts to complete conversion.

FORCE 120HP FLYWHEEL PN 817494A 2​

IGNITION WIRE HARNESS MERCURY 115 2 STROKE - PN 84-850045 A1​

MERCURY CRANK SEAL PN 26-828627​

FORCE 120HP BEARING CAGE ASSEMBLY PN 819312A 1​

DI3A7734 Mercury 0T005398 Stator Assembly PN 832075A 4 Fits 1993-2006​

MERCURY TRIGGER PN 855745A2​

4-MERCURY CDM MODULE COILS PN 3455 827509 A2​

1996-1998 FORCE/MERCURY OUTBOARD 120HP COIL BRACKET (I USED MY CDI BRACKET AND JUST DRILLED OLD COIL BOLT HOLES OUT TO BIGGER SIZE)​

1996-1998 MERCURY VOLTAGE REGULATOR PN 815279T5​

 

[Redbarron%%]

I changed a Sport Jet Mercury /Force 90 three cylinder from CDI to CDM modules.
Tracking ignition problems on a new to me motor was a PITA and I thought that the late model CDMs would be more reliable than the switch box, adapter candy bar and the coils in the original system.
The engine already had the red stator coil and I noticed that the #3 cylinder was intermittently firing and a quick check of the trigger coil indicated a problem there.
I bought the trigger coil and then started thinking about the CDMs .
I found 200 hp CDM cheap on ebay and saw a post that a trigger of over 4 volts would fire them and that they would work with the old trigger coils.
I bought a three cylinder ignition harness that was for a 40 hp (I think) to mostly get the plugs for the CDMs, but the entire harness was wired correctly according to the manual for the Sport Jet with the only thing necessary was grounding the common wire from the trigger (black and white as I recall.
I had problems originally because the colors did not match up correctly, but a timing light with the spark plug leads shorted let me figure out the proper firing order.
So far so good!.
I also installed a motorcycle rectifier / regulator so that the voltage would not go over 14.7 with a maintenance free battery fully charged and the engine at high RPMs.
As I understand it the old style trigger like I am using will work with the old style flywheel, but not the newer post 1996 flywheel which uses a different arrangement.
Original flywheel original trigger, late flywheel, late trigger, perhaps having Hall effect transistors, but I am not sure about that.
My feelings are that the late model CDM system will be much more reliable and robust as well as being readily available at a good cost used.
I think I paid $15 each for the three on my motor. They are from the 200 hp 6 cylinder and the part number was

827509T 7

.I cut a piece of 5052T4 1/8" thick aluminum to bolt on the original electronics plate and then fitted the three modules to that.
I did have to unscrew the ignition leads and put longer on to reach from my new plate to the plugs.
Fewer parts means easier to troubleshoot and fewer parts to fail.
I am going to buy a few spare modules to keep in the tool box since they are easy to replace.

 

[pnwboat]

The spark plug wire length will depend on how the coils are mounted. I found some 7MM diameter solid core wires on-line and have been using them. The larger diameter wires won't fit the CDM (coils) very well. I have had zero problems with the CDM ignition system since I put it on. One of the best modification to my motor that I've done so far.

 

[jerryjerry05]

Is this a double post?
Pastorbud started it and nofearforce seems to have taken it over?

 

[pastorbud]

Buncha wizards, you guys are! I'm pretty good with mechanical stuff, but the ignition stuff is all just magic to me.​

 

[pastorbud]

Is this a double post?
Pastorbud started it and nofearforce seems to have taken it over?

Actually, I just didn't understand how ideabooks work. Still kinda don't understand!

 

[NoFearForce]

Is this a double post?
Pastorbud started it and nofearforce seems to have taken it over?

I started an idea (project) in my ideabooks and pastorbud put it in the forum to see if anyone had done it yet. Which by the way, pastorbud was awesome and so very helpful. I just wanted to make a parts list so if anyone else wanted to do the conversion they would have the necessary information to do so. Oh and if I haven't thanked Pnwboat yet, Thank You soooo much for the help and information. It made life a lot easier than trying to dig and find this stuff.​

 

[NoFearForce]

Check this out pastorbud

https://youtu.be/aZFCKt_dOOc