Changing starter on 1991 115 Mercury any tips?

[stockdragrace]

Apparently I have a bad starter on my 91 Merc 115 motor. It cranks real slow, then finally fires, the battery is a new 1000 cca unit, and all wiring and connections have been cleaned to existing unit, any trick to changing the starter, looks like I have to remove oil tank to get access. any alignment issues that I have to look at as far as pinion and flywheel? Thanks for your help, Brad
Serial Number: 0D019809
Model Number: 1115412LD