Here is a hypothesis of what happened. The power wire (the one carrying regulated voltage at 14.7v ) is shared by:
battery (30amp) (problem)
ign (15amp) (problem)
Shift(25amp) (problem)
fuel pump (15 amp)
isc (15amp)
tail light (20amp)
The relays are rated for 15.6v (133% of 12v). They can only handle 35a in NC state and 20a in NO. Its the 20a NO that's the problem since a few of those relays operate in both modes. My guess is that the relays were arcing internally due to the voltage regulator and they can even weld themselves together given enough time. They can also be intermittent or go back to operating normal(ish). I would swap all the relays and all the fuses.
Sealed versions of the relays are the Song Chuan relays below, they are cheap from an electrical supplier. I think the reverse relay power draw is a red herring or just part of the above problem, swapping it should fix it. I had the shift fwd relay out for some reason when I took this.
4 pin = Song Chuan 303-1AH-S-R1 replaces Yamaha 8MS-H2189-00 |
4 pin relays can be installed text up or text down but should be up |
5 pin = Song Chuan 301-1C-S-R1 replaces Yamaha 8MS-H2185-00 |
5 Pin relays only fit one way, upside down (text down) |
View attachment 171088