1957 Mark 6 / Super Silent 6 Ignition

[sohcfour]

Hi all -

I have a 1957 Mark 6 (SN 954114) that I recently obtained. It's extremely clean and was well-maintained but was not run for about 10 years. I have gotten it running but with two small issues.

1. It's hard to start. While using my Quicksilver Service Monitor (aka an inductive tachometer), I noticed that the bottom cylinder doesn't have spark initially. It will start on the top cylinder and then the bottom cylinder will start to produce spark after a few seconds. Once this happens, I can run it up or idle it down as much as I want. It's idled stably at 700rpm, and I've had it running continuously without issue. Since the indicative tach is looking for current in the plug wire, it tells me that the wire isn't getting spark. So, point, coil or condenser right? What's the best way to test each of these? NOTE, this motor has the Bendix/Scintilla magneto.

2. Of lesser concern, I'm running off a gravity feed fuel tank (used for balancing motorcycle carbs). It takes the tank, primer, and pump out of the variables. Once I sort out the ignition question, I'll confirm that the diaphragm pump is working. Having tried to inspect it before, it's a bit of a bear to get out. Any tips on removing this in the event I need to replace the diaphragm?

Thanks!

Matt

 

[Chinewalker]

Pull the flywheel and inspect the magneto. If they haven't been replaced, the coils are going to be cracked - I haven't come across many original B/S coils that weren't. They're quite pricey to replace, but I have found a military spec coil that can be adapted. Those points are NLA, so treat them well - clean up the contacts. Condensers are available.

 

[Chinewalker]

Another option would be to source a Phelon magneto for your motor. Mercury used both mags on motors during that era. Mark 5 and Mark 6 would have both used the Phelon flywheel, cam and mag plate. I've found more with the Phelon than the B/S mags.

 

[sohcfour]

I just got the flywheel pulled last night. The coils appear to have been replaced, and look to be in good condition. The previous owner had a receipt from work done (I forgot to take it with me) and it had hundreds of dollars in parts.

Is there a way to test the coil? A target resistance or anything? As far as condensers, are they cheap enough to just replace as a matter of course or can they be tested? I will clean up the points.

 

[Chinewalker]

If the coils are intact, .ie no cracks or physical damage, chances are they're fine. The biggest issue with the B/S mags is the magnet tends to get weak. Clean points and clean mounting surfaces are a must. Condensers aren't terribly expensive, but are also easy to have tested at a small engine shop. Personally, I'd go for the Phelon mag - not a fan of the Bendix-Skinny-tilla mags myself...

 

[jimmbo]

I priced out a set of points for a late 60s merc 7.5hp, $100+(Can) each. I guess Brunswick really wants people to scrap their sweet old two strokes and buy new boring 4 strokes

 

[sohcfour]

The coils look great. Honestly they look like they're made out of cast iron to me, I'll have to check. They're surely not cracked. Maybe I can find a small engine guy to check the condensers for me.

I recently started the engine with an in-line spark detector (light). When it started, there was an indication of spark in the indicator light. But the engine was clearly running on one cylinder. When the cylinder being monitored with the spark indicator started firing, the light became brighter. Does this mean anything to anyone? For what it's worth, my inductive tachometers were showing RPM on both cylinders even before the second cylinder was fully firing.