2006 Yamaha F250TXR Starter engaging/grinding flywheel while idling

[CapeBound]

I have twin 2006 F250TXR's on my Center Console. When I start the engines, they start right up...no issues. After a minute or two at idle (in neutral), my starboard starter will pop up and engage the flywheel causing an awful grinding sound. We popped the cowling and manifolds to check all connections for corrosion. They are all clean and tight. My hunch is that it is the solenoid going or a short either in the key switch or relay. It was recommended that I swap the starters in the two engines. The theory he had was that if the starter that was engaging the flywheel in neutral did the same thing when switched to the other engine, then the starter solenoid is bad. If the other starter does the same thing on the same motor, then it must be the key switch.

Anyone have any experience with this problem that can offer some advise about where to start or ways to diagnose the problem? I don't want to buy a $500 starter to find out that it's something else.

Thanks!

 

[CapeBound]

Just an update...I swapped the starters in the engines and the problem persisted in the same engine (so, not a problem with the starters or solenoid). I then swapped the relay from the engines and the problem also persisted in the same engine (so, not the relay). Is my problem most likely in the key switch? Is there any way to test the switch to see if it is causing a short that is energizing that starter to engage the flywheel? Anything else I might be overlooking?

 

[99yam40]

the switch or some wiring / connector is making a connection when it should not
have to chase it down.
if it will not happen still while in gear then the neutral safety switch should take the key switch out of the equation

or you can start disconnecting the wire from key switch at different places to eliminate sections of the wiring and devices