Merc 20H ignition update to CD

[Mike 41P]

I'd like to get my 20H out more often. One thing I'd like to have though is a CD ignition. The first thing I thought of years ago was the 25SS ignition, so I pulled both flywheels and found that the taper was different. I did not persue it further and I'd like to hear of anyones work or speculation on this topic.

I also like having the 20H running in 250MH and the rule right now allows the motor "as raced in 1987 SO", which Jeff says prohibits any change to the ignition. So we would also need a rule change to say "except that the ignition can be replaced with CD igniton, maintaining the top cowl/rewind starting system"

Did Mercury ever use the same flywheel taper on a later engine with CD?

Could the 8HP steel CD flywheel now being used by Sidewinder be rebored to the 20H taper? I know there is a version of the OMC CD2 that is completely housed under the flywheel. That would be esthetically the ideal way to keep it totally concealed from view.

[Chairman]

The under flywheel ignitions that I'm familiar with (for the 31.8 motors) are all rev-limited at 6100 rpm.

[Mike 41P]

I know many of the external CD2 have limiters, if all underFW have em then just can't conceal it. Looking for info and ideas.

[dwhitford]

The self-energizing Motoplat (Spanish, I think) that Mike Schmidt installed on my Quincy 250 20 or so years ago reguires no battery and obviously has no rev limiter because I tached 10,320 at Wilson several weeks ago, and I never aired the boat completely out. The Motoplat's coils are external. Everything else (whatever that might be) is under the flywheel.

You might also want to check what the PRO guys run on their Rossi enginies at almost 14,000 RPM: very simple stator-plate pickup sensor, but also external coils like my Motoplat.

[ZUL8TR]

Also try David and Alan Van Weele at :

http://www.aeroliner-boats.com/index.html

They are involved with a company that makes CD Electromotive Ignition Systems for their 4 cylinder mod Merc race engines. They just might have an application or can get one produced ($$?) for the early 2 cylinder ignition point Mercs like the 20H, KG4H, KG7H, and others? Alan still actively races in NBRA.

[Art K]

I installed a electromotive system on a a merc 25 that we ran in NBRA C- Mod. Was more than competitive. Got rid of the 9lb flywheelfor a less than 1 lb flywheel. Really turned that engine on. This system uses a battery. The one i used came from Cabelas, weighed less than 2 lbs,cost 19 bucks. Would run all day on that battery.
Art K

[reed28n]

Could probably sell that popper as is and add the money you will spend fabricating a new CD ignition off something else together then invest in a new Side Winder and a restrictor and race two stock classes at all your Region 3 and 4 events.

[runabout333]

Try to find Mike Petty on Facebook.. He has built a 20-H mod. motor with an OMC ignition.
He lives in the east coast of Central Florida. If you can't find him,, get in touch with Bill Giles as Bill
just built Mike a new hydro. Bill might be able to get you a phone # or email addrsss.

[Mike 41P]

Thanks for all the ideas. I know about Motoplat but they are just not available any more, I have a dead one sitting here and can't get parts. Also the Mod commision will probably require any flywheel to be similar in weight to the original. I'll look into Electromotive. The OMC is top of my list since it is so available. Does anyone have real info about reboring a flywheel to put Merc taper in the OMC flywheel?
Mike Thierfelder

[Bob Dunlap]

OMC 9.9 and 15hp and other flywheels fit the 20 H taper. You can use the complete 9.9 or 15 complete ignition and it works great with very little work to make the OMC stator plate fit. Turn the flywheel down and u have the best cd ignition in the world (no battery required). But it will never b approved by APBA.

[Mike 41P]

Well then that does make it easy, it is great to hear the 9.9/15 OMC fits. The first thing I had looked at was the 6/8 OMC flywheel that we use on the HotRod/Sidwinder, it does not match. Now, if I can find a STEEL 9.9/15 FW and machine off the ring and knobs on top it will look and weigh very close to the original. AND if there is an under FW CD2 without rev limiter then it can all be concealed and a casual look at the 20H will look like stock. If this works I will submit to MOD commission and I think they would likely accept. It would be a reliabilty, not performance, change and the stock 20H in 250MH has been a good fit.
It would be good to hear comment on this from Jeff and Tom before I go looking for the parts. If this were seen as DOA then I won't bother.

[Mike 41P]

General MOD rules allow this type of ignition change. It could be done on a 20H which would be legal in 350HM, along with stacks or pipes. But it would not be fun because it is still way short of competative. But the stock motor is reasonable in 250MH, not likely to win (w/o some jumpers) but the best can place high. Its the same thing that has kept me running my 25mod OMC in 350MH here in the east where 400MH does not exist. I think this ignition change would be in keeping with the spirit of the "as raced in 1987 SO" rule for 250MH.

[Mike 41P]

OK, I got an OMC 15HP flywheel 513972. It is 6LB 7oz vs 4lb 13oz for std 20H flywheel. This is a cast steel wheel like Sidwinder is using, so it can be cut down safely. After removing the rope ring and recoil ring it will probably be around 5lb, a good match to the original. Both of those have to be removed to make it fit under the 20H cowl.
Looks like a good start, but while the taper is right, it does not sit down quite far enough. Is there anyone out there machining-wise who has the set up for the 20H taper, who could both turn down the rings and also releave the taper enough to seat it correctly on the crank? AlanB, Darrel, TJ, LT?

[A/B Speedliner]

I believe Doug Kay can do the correct 20 H taper. He has made KG Phelon wheels fit a 20H

[Smitty]

FWIW, in the late '60s Chuck Walters got the taper on the 20H crank in his A looper turned or ground down to take the KG-4 ignition that had the magnets that slid over the shaft, inside-out compared to a Phelon flywheel ignition. The alteration allowed him to use a cut-down, lightweight flywheel. I used to have this stuff in my head, but it's fading now; was that inside-out ignition a Bendix-Scintilla, something like that? I do recall that the guys who used them preferred the clear coils to the brown coils.

[bh/]

I was wondering if one searched the APBA rule books, if the Bendix-Scintilla mag as used on the M20 was legal for use on the M20H in Bstock. This would not be a step forward, but if it were, then it would be legal on a Bmod motor now.
But, just use the steel B-S flywheel. Source a suitable magnet flywheel from a chain saw or ?,
press it on the crankshaft, source two integrated CD type coils, swap them out for the stock coils,
and now one has a modern, reliable, pointless CD ignition on a M20.
The B-S flywheel would match right up to the recoil.
If the B-S is legal in Bstock, the rest of the mods should be also .
Dieter sourced his CD ignition for the VC from Poulan, and we called it the pork chop ignition.
I would love to present one to inspection.
Bob Goller would be struck speechless . RC ...???

ps; -thinking out loud, the B-S is legal on a KG7H , and it can be upgraded with 20H parts
-so present the 20H as a KG7H

[rumleyfips]

Dave:

Mod rules state that a small taper flywheel cannot be bored for a 20H crank. I assume there were two different flywheels cast.

[rumleyfips]

Brian:

I doubt you'd slide that KG7 argument past many inspectors. The only KG7 parts I remember fitting a 20H were reeds, rings a few gaskets and port covers . A 2oH parts list would show only a Phelon mag. KG7 parts were legal in A stock and Mercury produced extra blocks and pistons to keep people happy.

[rumleyfips]

This thread got me Googling and I learned a lot.
Condensors produce longer duration spark than CD ; sort of a poor man's MSD. Longer spark ignite the mixture better and result in a more complete, more even burn and higher pressure on the pistons.

Plugs fire at the lowest useable voltage. Good wires and plugs with sharp edged result in more headroom.

Wider plug gaps use more voltage but with headroom can result in a better burn ( similar to longer duration ).

Points don't bounce at 7000 rpm.

A 20H doesn't have enough compression or turn fast enough to need super high voltage.

The stock ignition needs about half an hour's attention before a race but has some advantages.