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77 Honda B75, no spark

D

dillon

Member
Where do I start? The motor sat protected for about 25 years, no loose connections other than the kill switch being disconnected do to the button being broken, its not grounding. Although the points looked clean I cleaned them anyway, new plugs. I know both plugs need to be connected to spark. At this point is there a certain electrical component that might go bad from sitting? Or what this most of the time ends up being? Its really a clean motor, nothing broken, etc. and I would love to bring it back to life, just can't get spark. Any advise would be appreciated.
 
Hi,
I'm no expert on these but have worked on a few of them.

Some of the old ones had a neutral safety switch that would get out of adjustment and ground the primary (or ignition exciter) coil. If your's has one, it will be located on the shift lever shaft under the hood. It is a magnetic reed type switch and might be stuck closed if the motor was stored in gear. There's a sort of "bent Y" looking blocking plate on the horizontal portion of the shift lever shaft you can locate for identification. If the switch is stuck or out of adjustment, unplugging it will allow the ignition to work. But, the outboard will then be able to start in gear.

If no switch, use a multimeter to check for continuity of the primary (exciter) coil that's under the flywheel. Resistance is listed as 2 Ohms.


If the coil isn't open, check for power from the primary (exciter) coil under the flywheel while pulling the engine over. If the primary coil isn't producing voltage, I might suspect rust build up on the coil core feet or flywheel magnets or both.

Sometimes, during storage, critters can build nests or spider webs that interrupt the function of the magnets.

You will need to pop the flywheel off to check for that or possible primary (exciter) coil failure.

Other possible issues would be with the ignition points capacitor (condenser) or maybe the wiring touching ground where it shouldn't.

The capacitor should be around 24 MFD (microfarad). I found a Borg Warner made replacement that worked but that was years ago.

Good luck, I hope you get it going and please let us know what you find.
 
More specifications:

Ignition coil:
Primary winding resistance = 1.5 Ohms

Secondary winding...
...Measure by inserting test leads into both spark plug caps, one lead in top cap the other in the bottom. This puts cap contacts, and plug wires in series with the Secondary windings.....BOOK says 8k Ohms + or - 20%
BUT...
...I found resistance on good running outboards to be higher than that...up to 31.5k Ohms.
That could be due to replacement coils I'm not sure but that's in my notes.

Ignition points gap= 0.012" to 0.016"

Spark plugs: NGK DR 5HS
Gap= 0.024" to 0.028"

NOT Ignition related but often has NEVER been adjusted or checked....

.....Valve clearance: 0.002" to 0.004" for BOTH intake and exhaust valves In other words, ALL valves.
That's unusual for most engines but that's the spec for these little old gals.

Good luck with your investigation.
 
jgmo said:
More specifications:

Ignition coil:
Primary winding resistance = 1.5 Ohms

Secondary winding...
...Measure by inserting test leads into both spark plug caps, one lead in top cap the other in the bottom. This puts cap contacts, and plug wires in series with the Secondary windings.....BOOK says 8k Ohms + or - 20%
BUT...
...I found resistance on good running outboards to be higher than that...up to 31.5k Ohms.
That could be due to replacement coils I'm not sure but that's in my notes.

Ignition points gap= 0.012" to 0.016"

Spark plugs: NGK DR 5HS
Gap= 0.024" to 0.028"

NOT Ignition related but often has NEVER been adjusted or checked....

.....Valve clearance: 0.002" to 0.004" for BOTH intake and exhaust valves In other words, ALL valves.
That's unusual for most engines but that's the spec for these little old gals.

Good luck with your investigation.
Click to expand...
Thank you!
 
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