When a motorcycle photo became a boat

[peterbaron]

The best for diags is if you could provide your F115 starting system electrical diagram, but I assume it looks like this one below with 4-prong relay.... and I make my diags based on THIS diagram below:




Your thinking is correct, and it sounds like a voltage drop during starting

1. you: 
The motor won't start or turn over when I turn the key.  It only makes a click.  However, when I short the terminals of the starter relay with a tool, the motor turns over and starts right up
me:
I assume that you removed your relay and bridged SWITCH terminals 1 & 2 of the start relay when the ignition is ON and your Yamaha runs  = black, green and red circuits  / LEFT side of this starter relay diagram have no isue, as well as components such as battery and starter/solenoid- integrated unit
..... but ignition switch "START" circuit needs to be verified

2. you:
I bench tested the old relay and it appeared good.  However that was not under load, so I can't really confirm it is good.  But since the new and old relays act identically, I think they are not likely the issue.
me:
this is correct, also the relay coil resistance between terminals 3 & 5 should be around 70 Ohms - automotive standard, but may very from 50 - 150 Ohms

You most likely have a problem on the coil circuit side like wires, contact points/ RIGHT side of this diagram - either pink/B+ or black/NEG/ground controled by the ECM

MARINE may have a total different set up, so my diagram is just an electrical troubleshooting idea.

Here is AI
https://www.google.com/search?q=f115+sta...AEYASABKAE

https://www.google.com/search?q=f115+mot...s-wiz-serp