mercruiser base timing

[brian3127]

I have a 1989 smokercraft with a mercruiser 3.0 engine. I had to buy a plug that goes into the ignition module so I can put the engine on base mode. When I start the engine and then plug it in and connect to 12v the engine rpm does not drop at all so what does this mean.

I thought I read somewhere that if the rpms don't drop then most likely you have an automotive ignition module. Is this true and if it is what would the part number be that I need to order