C115 starter issue

I have a 2000 C115TLRY- am getting it ready for the season and trying to start it on the garden hose. I'm finding that the starter motor barely spins the motor over- certainly too slow for it to fire. The battery I'm using is fully charged and reads 12.7 volts on the voltmeter. I get the same voltage reading from the + lead on the starter relay from the battery. I'm able to turn the motor flywheel around by hand and nothing seems to be binding. All connections seem tight with no corrosion. I did not use the motor at all last year- it was in storage. I have not had the starter apart so do not know the condition of the brushes or other internal components. Any thought on how to proceed from here? Thanks in advance.

I am happy to advise that I have found the problem. After searching the forums for suggestions, I ran booster cables from the battery directly to the starter- the starter spun over very quickly. After doing that, I re-connected the + cable from the battery to the starter but instead of re-connecting the - lead I used the - lead from the booster cable. The starter spun quickly. That told me that the problem was the - lead to the battery. On closer inspection of the rubber shield, I found a hole in the shield that had allowed water to enter the copper core. Hope this post helps others with a similar problem.