Need motorhead input

I am replacing a starter motor in merc 25ELH. After install the motor engages but will not disengage. I've ordered a new solenoid hoping that's the problem. Anyone got a comment if this the issue, or something else? Thanx 

I have a 1989 Evinrude 60 HP that apparently is only supposed to use a wet cell/lead acid/flooded battery and not a maintenance free battery or it will burn out the rectifier/diode. Has anyone else had this problem?  

Is there a way to solve the problem without buying a new battery which is harder to find a starting battery?

Thanks in advance for your input.

Let us know if that shim works

Well, I got some help from another section of this site. I added .060" shim and compressed spring. Seems to work. Will find out tomorrow.