2003 Yamaha F90TLRB four stroke issues

I was idling forward, motor died, would not start, electrical smoke and smell (plenty of oil and the water pump was functioning perfectly). Noticed the 30 amp circuit fuse was blown, replaced fuse and it immediately blew again. Disconnected the yellow wire for the limp mode and engine will start and run. Anybody out there know what would cause the 30 amp circuit to blow on these motors when the yellow wire is intact and what the yellow wire actually does for the ignition control? I have a feeling it’s something in my ignition switch that is grounding out and causing the fuse to blow. The dealerships are taking service calls in July, hoping I can figure this out before then, any help is greatly appreciated.

Update: did some more digging, my rectifier is burning up, the big question now is is it just a faulty rectifier that wore out or do I have a grounding issue that caused it to burn up??? Still checking on my connections, was hoping to find a worn insulator or some loose grounding wire

As I said in the other post, are your battery connections clean and tight? Not wing nut tight but actually tight with a wrench? And the connections are clean?

onestout wrote:

As I said in the other post, are your battery connections clean and tight? Not wing nut tight but actually tight with a wrench? And the connections are clean?

This was exactly the cause of my Mercury blowing the 30 amp fuse. However, I did not have any smoke and smell because of it.

Go get your rectifier replaced. I waited all summer last year waiting on a wiring harness from Japan that fried from this same problem. I can only imagine how long it will take with this covid stuff going on. Its a common problem in the older 4 strokes

Yes, very simple to replace the rectifier, ended up bringing it in to make sure that I didn’t have an electrical issue that was causing it to burn up, I didn’t want to replace the part and then have it burn up again right away, $280 for a Yamaha rectifier. I keep my battery connections very tight with a lock nut and clean them yearly. They couldn’t find any electrical issues at all, simply a failure of the rectifier after 18 years, replaced it, I ran it on Mille lacs for quite a while and it’s running perfect again. First repair on the Yamaha besides maintenance in 18 years!

Good to know. Thanks for sharing. I have an ’04.