i have a 2005 f225 yamaha. when i turn the ingnition switch to start the starter does not engage the flywheel. i switched the starter with my twin and the good starter does the same thing and the problem starter works on the twin. i bypassed the battery switch and get the same results. switched the battery from the known good motor and get the same results. i switched the relay that is attached to the starter solenoid with a brown and white wire and get the same, relay is known good on twin. power drops at starter when ign is in the start pos to approx 6v. dont know where to look for bad grds on the engine can any help?
Might be nothing more than loose or corroded battery terminals, or weak battery.
checked cables and switched from one set of batteries to the twins battery and same thing and the twin works fine all four batteries are new prior to last trip. problem started after the trip all connects i can see are clean but i quess i will check agai. but i would think by using the known good battery from the twin would rule this out.
Is the starter armature turning but the bendix is not engaging the flywheel? Try using a pair of jumper cables to ground the starter to the battery. I'm not experienced with marine engines but a start circuit is pretty basic. Look where the starter mounts and you just might find a power or ground cable that needs some attention.
i always check the simple things first but this time i got burned after all that checking i went back to basics and checked cables for corrision and found they were hand tight but not tight i put a pair of pliers on them and tightend. problem solved.