There's a couple of full time motor recyclers on ebay. I've been well satisfied with "Northland Outboard Salvage Marine". If you personally figured out that the ECM is actually the problem, then you are likely in the market for used parts too. I did and worked with Northland, late last summer, for the ECM on my much older yammi 90. Well, a bit older than yours. Part works great, solved my problem and I ran it nearly every weekend from August through the beginning of December. Also, they would replace it if it turned out broken in the first place.
Really, know the part you need and know how to identify it--ECMs aren't cheap, but they can be reliable.
Contact Northland, through ebay messages. They'll work within the rules and complete the sale on ebay.
'till next time,
1987 Whaler Super Sport 17, Yamaha 90
1981 Whaler Sport 13, Johnson 50