Can I do this???

I have a powerhead and control harness from a 1998 Yamaha 90TLRW. I just put it on a 1984 90 ETLN because the 98 was iun saltwater and just about everything was shot. The powerhead on the TLRW was rebuilt. Everything seemed to go together just fine, but I see that the trim unit on the ETLN is a 3 wire and the wires are significantly larger than the two wires that I had on the TLRW. After toasting the relay on the TLRW, I removed the relays from the ETLN and mounted them into the location where they were, but I am having no luck . Now the key switch will not activate the starter. I have jumped the solenoid and the starter will engage just fine. I fear that I may have toasted the harness. Can anyone give me an idea of what happened or how I can remedy this? I dont want to just start buying parts..

Thanks

[boats.net]

Have you checked the fuse on engine?