Low voltage to 1 coil. 1988 50 h.p. 507Y8D

Good evening,
The last time my father and I had the boat out in October, we lost spark to one cylinder. Tonight we went about diagnosing the problem and here is what we have come up with.

There is very weak spark to the upper cylinder.

When cranking the engine the wire feeding that coil from the "power pack" is only putting out @5.5 volts.

The wire feeding the coil for the lower cylinder is putting out @ 12 volts.

Both of these test were done with the coils disconnected.

Both coils read the same ohm resistance between primary and ground and primary and plug wire.

If I switch the primary feeds from the "power pack" to the coils then the lower cylinder has the weak spark.

So, I believe we have determined that the coils are fine.

The best I can tell from the wiring diagram in my Seloc Manual is that the only other parts of the ignition system is the "power pack" and the ignition trigger under the flywheel. So it seems that one of these items is faulty.

Has anyone come across a similar situation or have any suggestion on to how to best determine which of these items needs to be replaced?

Thanks for your help,
Erik

Re: Low voltage to 1 coil. 1988 50 h.p. 507Y8D

By switching wires you have proved that both coils and triggers are ok. The only remaining component is the power pack. This box has two sides and two circuits; one to fire each coil. It is possible that only one side has failed. Because of the expense, see if you can borrow a known good one before buying one: Electronics are usually non returnable if they are used and don't solve the problem.