I have a 2001 mercury optimax 225 two stroke engine. The serial number is 0t305247. It has a mercury smart craft display. The smart craft gauge is good at pointing me in the right direction when a problem arises, but I would like to have a diagnostic tool for more detailed information. Am I wrong to assume that an 18 year old diagnostic tool can be purchased cheap? Is eBay and amazon the best place to look?