obsolete coil

[mroman59]

Hey guys, I have a 10 HP Honda outboard motor, 4 stroke with points & condenser, for which the coil is obsolete. As far as I
know it is a 6 volt system because the coil says 6 volt on it. It was manufactured in 1978. The coil is a dual spark ignition
coil and I was trying to match up coils with similar primary and secondary resistances, but I have had no luck. I found a 6
volt coil made for a motor cycle for which the primary and secondary resistances are double that of those of mine. So my
question is, is there a way to use this coil and reduce the resistance values using a resister? If so, where do I get them and
what do I need to know before trying something like that. My other option is to try to find a 12 volt coil , but that requires
changing over to a 12 volt system and I still may have a problem matching resistance values and would need a ballast resister.
Changing over to a 12 volt system does not seem that expensive when I look at parts needed. Another thing I thought about is
getting rid of the points and going to electronic , i.e. if I can find a company that makes something for this size engine.

This engine is a simple pull start and does not have battery ignition and does not run any lights etc. It does have a charging
unit to charge the trolling battery.

If anyone can point me in the right direction, I would appreciate it.
Mike

 

[JMOR]

(quoted from post at 13:18:13 10/09/18) Hey guys, I have a 10 HP Honda outboard motor, 4 stroke with points & condenser, for which the coil is obsolete. As far as I
know it is a 6 volt system because the coil says 6 volt on it. It was manufactured in 1978. The coil is a dual spark ignition
coil and I was trying to match up coils with similar primary and secondary resistances, but I have had no luck. I found a 6
volt coil made for a motor cycle for which the primary and secondary resistances are double that of those of mine. So my
question is, is there a way to use this coil and reduce the resistance values using a resister? If so, where do I get them and
what do I need to know before trying something like that. My other option is to try to find a 12 volt coil , but that requires
changing over to a 12 volt system and I still may have a problem matching resistance values and would need a ballast resister.
Changing over to a 12 volt system does not seem that expensive when I look at parts needed. Another thing I thought about is
getting rid of the points and going to electronic , i.e. if I can find a company that makes something for this size engine.

This engine is a simple pull start and does not have battery ignition and does not run any lights etc. It does have a charging
unit to charge the trolling battery.

If anyone can point me in the right direction, I would appreciate it.
Mike

ou say that it does not have battery ignition. That sounds like it is magneto. Is the assembly mounted in very close proximity to flywheel? Does it have laminated iron part nearly touching flywheel?

 

[JMOR]

(quoted from post at 14:46:00 10/09/18)

(quoted from post at 13:18:13 10/09/18) Hey guys, I have a 10 HP Honda outboard motor, 4 stroke with points & condenser, for which the coil is obsolete. As far as I
know it is a 6 volt system because the coil says 6 volt on it. It was manufactured in 1978. The coil is a dual spark ignition
coil and I was trying to match up coils with similar primary and secondary resistances, but I have had no luck. I found a 6
volt coil made for a motor cycle for which the primary and secondary resistances are double that of those of mine. So my
question is, is there a way to use this coil and reduce the resistance values using a resister? If so, where do I get them and
what do I need to know before trying something like that. My other option is to try to find a 12 volt coil , but that requires
changing over to a 12 volt system and I still may have a problem matching resistance values and would need a ballast resister.
Changing over to a 12 volt system does not seem that expensive when I look at parts needed. Another thing I thought about is
getting rid of the points and going to electronic , i.e. if I can find a company that makes something for this size engine.

This engine is a simple pull start and does not have battery ignition and does not run any lights etc. It does have a charging
unit to charge the trolling battery.

If anyone can point me in the right direction, I would appreciate it.
Mike

ou say that it does not have battery ignition. That sounds like it is magneto. Is the assembly mounted in very close proximity to flywheel? Does it have laminated iron part nearly touching flywheel?

o edit feature, so I will add that if it does not need a battery to run, then it is a magneto and coil replacement will likely be difficult to impossible using some sort of substitute.

 

[Steve@Advance]

Are you sure the coil is bad?

If you were able to check resistance, it should still work unless the case is cracked. Are you getting voltage to the primary side when cranking? And ground through the points when closed? I believe both plug wires need to be connected to test spark, both plugs will fire at the same time.

Adding a resistor to a coil with already too high resistance will be going the wrong way.

Is this it, or maybe a lead...
Coil

 

[mroman59]

No I am not sure the coil is bad. I just heard of many people who said there motors ran fine and then when it died on full throttle, they found out it was the coil. Supposedly the coil heats up and then dies. I was just thinking this is my case. Some say the condenser can behave like that also.

I took the resistance of my coils. they are: primary = 0.33 and 3.3K ohms. The book says primary should be 0.56 +/- 10% ohms and secondary should be 8k ohms +/- 20%. I checked my readings with 3 different meters, however I want to use a high quality one before determining if it is bad. I will ask my mechanic if he has a good one.


If indeed my coil is bad and the coil is obsolete and most other coils are of higher resistance than my coil and most are made for a 12 volt system, does anyone have any suggestions on what to do?

 

[mroman59]

Yes, this outboard is a pull start and no electric/battery start option. It has a primary coil under the flywheel and there are
magnets. It has a charging coil designed to charge a trolling battery and points & condenser. Its a 4 stroke engine. Tell me if
I am missing any needed information. Thanks, Mike

 

[mroman59]

The ignition coil is mounted very close to the flywheel. The primary coil and charging coil are located under the flywheel. The
points and condenser are located under the cam cover. The coil has laminated metal (I think that is what you are referring to) on
each end and these ends have holes drilled through them, for mounting. The coil is mounted to the engine block. The top mounting
screw is next to the positive terminal where the wires from the points, rectifier and kill switch connect. This top mounting
screw sits just below the flywheel. The bottom mounting screw is about 3-4 inches away from the flywheel, as the coil stands
vertical. The coil is cylindrical in shape.

Below is the link to the parts diagram if that would help:

http://peparts.honda.com/marine#/browse/oe/bf/bf100/BF100-LA

 

[JMOR]

OK, got it. About same as many Honda small MC & old 3 wheeler ignitions. The part called 'primary coil under flywheel' generates the electric power to power the ignition coil. It could be a problem just as well as could be the ignition coil. Condenser too. Most such electrical parts can fail under heat conditions and often seem OK when cool. Does not run, no spark, weak spark or what?
Does the 'primary coil under flywheel' put out a voltage when cranked? Sub-Ohm measurements are very difficult to accurately measure, so I would not condemn on that basis right away.