Hey everyone need some serious help as I put a new motor on my boat and the started is not engaging for some reason? I have heard of shimming the starter but what exactly is that? Also is that what I have to do or is something else wrong. All it does is spin and doesn't engage. Took the starter to get tested at auto parts store and it passed as I thought it would since it's practically brand new. What do I need to do?

When they tested it did they make sure that the gear moved forward? That is likely your problem. Depending on the starter you have you may not be getting enough power to it to push that forward.

Excellent point .... you need about 10 volts ( Actually about 9.7 volts) while cranking to get the Bendix to engauge ....Ideally you need to check the Voltage at the starter but you can check at the Solenoid ......m

Had the same issue and as mentioned the voltage was low. Seems to work fine now, but it does concern me that maybe something isn't optimized....

Both batteries were charged and it just kept spinning and not engaging. Maybe I'll try hooking up the jumper too to see what it does

Batteries are just one function .....you really need to check the voltage at the starter under load ....could be a cable ...cable end ......motor gnd ..... a good check is to run a wire from the same stud the Battery feeds on the starter long enough to be able to get voltmeter leads on while cranking ..... that will tell you if EVERY componet is good all the way to the starter .....m

Ck The Grounds

Also Thers Two Sets Of Bolt Holes Move It To The One Closest To The Pan