1967 20 not firing

[wbmiller3]

Just acquired a 1967 20 hp mercury (sn# 2032385). Paid a hundred dollars for it as it's not firing. Fellow said it was running great always has when it just died. I pulled the cowl and flywheel off and everything looks new (well almost) wiring is excellent, everything is fairly clean etc... kill button was already disconnected so he must have tried that. He didn't want to get into pulling the flywheel (harmonic balancer puller worked great) Got an old factory service manual on ebay, and they say to use a mertronic magneto tester. The few I could find for sale were ridiculously expensive. Any advice on how to trouble shoot my problem without one of these? Points aren't grounded and look good, gap seems normal, not the kill switch or any obvious wire problems. Everything is extremely clean and before I bought it I checked the compression on both cylinders (fine).

Thanks, Wayne

 

[Chinewalker]

I've found that the coils are USUALLY good on those, unless they are visibly damaged in some way. The points should be shiny clean and gapped a .018". The weak point is the condensers. I've replaced some with OEM, if I can find them, but I've also used OMC (Evinrude/Johnson) condensers. The electronics don't know the difference.

 

[wbmiller3]

Thanks, I'll give it a try

 

[flyingscott]

Are you sure you do not have spark? Have you done a compression test?

 

[60sboater]

He said he checked compression.

I have a '67 20hp too (from CL for cheap,was running) with a damaged cylinder...other stuff ok. You can do a crude test of the caps/condensers with a ohm meter...analog ones are best for this. Choose a scale...maybe R x 10 or R x 100 to show charging and discharging as you connect the leads one way,then the other between the lead and body. This can show a shorted or open...pegged for short,no needle movement for open...maybe try R x 1 scale too. Some DMMs have cap testers built-in,like a Fluke 12.

It's a little unusual that both are not firing.

 

[wbmiller3]

Picked up a set of condensers and points on ebay (don't have them yet)... holy ___ their proud of those! guess its the short year window. Supposed to be NOS. Coils look fine, compression was excellent and even. To be honest I personally didn't check for fire, fellow I bought it from was pretty sharp, seemed like the type who could tell if a plug fired, I just took his word for it. I checked compression, verified the kill switch was disconnected and pulled the flywheel. Felt pretty confident I'd find an obvious problem, which I didn't. I've got an expensive Fluke not sure what model, never checked a condenser before though, guess it's time I learned how.

Thanks again, hate to see the prices so high on these components. I love the old ignition systems.

 

[60sboater]

Yes,the old stuff is $$$.

 

[EchoNovember]

Pick up a cheap spark plug tester and check to make sure you have a spark, too. If your ignition system tests good, then check the carbs and make sure fuel is getting to the bowls. The fuel line or filter could have clogged, no fuel no ignition. After checking to make sure you have spark, check to see if its a fuel issue by spraying some Seafoam down the carb throat like starter fluid and see if it catches. The white smoke means it's working, and the bonus is cleaning things out. Just don't do it too much as it doesn't really lubricate anything. It will let you know if it's a fuel issue, though.

I'd rebuild the carb preemptively just to make sure it doesn't cause problems later, though. I can get you a link to a parts list and a source of parts for your motor if iBoats doesn't have what you need.