Testing a Mariner switch box

[thepetrolist]

Today I started working on a 2000 (?) Mariner 20 hp for a customer. First time for me working on an outboard this new, but I thought what the heck, I’ll give it a try!

According to the customer, the engine stopped running and wouldn’t start. He started the engine, it ran fine, then he shut it off since he forgot something in his car and had to get it, and when he returned it wouldn’t start. It is completely dead with no spark whatsoever on either cylinder.
It has one coil per cylinder. If one would have failed, then it would spark on the other cylinder, but it is completely dead on both.

I checked the sparkplugs, wires, coils, all electrical connections, all switches, and everything seems to be in working order. That leaves the switch box as the main suspect.
Is there any way to test its function? I read somewhere that the only way to determine that the box is shot is to make sure everything else works, still no spark, = box is shot.
Is this true? I’d like to be 100% sure it is the culprit before I order the part and charge the customer for it..wouldn’t want to do it unless necessary.

Otherwise the engine seems to be in great condition.

[ken-w]

Go to http://www.cdielectronics.com/, great site I use it to gather troubleshooting information. The installation manuals have troubleshooting tips.

[jeff-register]

More than likely the SCR in the switch box.

[Mumbles]

A friends Merc had the same symptoms as your motor and after discussing it with the owner, we decided to take a gamble and lay out the coin for a new switch box. The gamble payed off and the motor runs flawlessly now!

[legendre]

quote Jeff Register:

More than likely the SCR in the switch box.

Can it be serviced, or are the electronics all sealed up?

[fleetwin]

I am not familiar with the merc system, but am "assuming" it is similar to the OMC set up. If so, you might want to start by removing the stop circuit/safety switch/key switch from the circuit to ensure it is grounding out the system. Check all grounds and connections too before putting out big bucks for that switch box.

[debe]

I have dug out the potting compound on a Evinrude 3 cylinder CDI unit & replaced the SCR of the faulty cylinder. Its one of those jobs you have nothing to loose if it fixes it. The price on some of the CDI units is rather expensive. Here in Australia Jaycar sell a CDI kit which ive built several & used. There price is around $25 Aust, & you need one for each cylinder.

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