Re: 2hp Johnnyrude electrical problem

[Don]

Yeah, if it is arcing between the throttle control and the frame, then the mag plate is not properly grounded. Are you getting shocked when you touch the throttle control?
I would definitely use an ohm meter and check the mag plate for ground before going further.
Calibrate the ohm meter to the low scale, connect one lead to a good clean ground on the block, not the place on the exhaust manifold where the ground lead is currently connected. Now connect the other lead to a good clean spot on the mag plate, not the place where the ground strap is connected.
The meter should read less than one ohm, as close to zero as your meter will allow when calibrated properly (two ohm meter leads connected together.
A reading above one ohm (or more than a few 10ths higher than your calibrated reading with leads touched together), means the mag plate is poorly grounded. These ground leads are a trouble spot, and often overlooked when these engines are used in salt water. The connection on the exhaust manifold gets rusted, and there should be a star washer between the ground strap and the exhaust manifold. The manifold cover is not the greatest ground to begin with either, so be sure the bolt threads and shank are cleaned up well. The little mounting screw under the mag plate is usually rusted as well, oftentimes breaks off when you try to remove it.
Keep in mind that the lead might be damaged, having only a few strands actually conducting the ground path, the ohm meter would fool you in this case.
I guess I should have started with the simplest troubleshooting technique first! Connect a decent jumper lead from a good engine ground to a clean ground on the mag plate while the engine is arcing or missing. If the miss clears up/arcing stops with the auxiliary lead connected, you have a ground strap problem.