Starter troubleshooting - how to tell if its dragging.

[slag]

I'm working on a slow crank issue with my starter and am trying to troubleshoot the starter in particular to see if its the problem and need some advice. I have a 98 Wellcraft 2000SS with the 5.7 liter 260 hp engine. I have a sierra 18-6275 starter (staggered mount) that has worked great for the past 3 years. This weekend, it started turning the boat engine over very slowly and would sometimes not work at all. I pulled it out and clamped it in my vise and tested it with a good 12 volt battery. When engergized, it would spin over, but voltage on my battery would drop from 12.66 volts to 11 volts (this is with no load), and then climb back up to 11.5 volts. I compared it to a used mercruiser starter I had as well, and the sierra starter doesn't seem to have the oomph or run as long after power is removed as the mercruiser one does. What's a normal voltage drop under no load? Oreillys and Advance couldn't bench test the starter for me they said, so I'm trying to figure out if its worth opening up and cleaning it up or if it is performing as intended. I also cleaned all the battery and starter electrical connections as well as block ground, but don't want to put this starter back in if its suspect. Thanks for reading this wall of text.

 

[jerryjerry05]

Starter, take it apart and clean it.
​Pull the drive off and see if that makes a difference?

 

[slag]

I did clean the starter last night and it seems to operate a bit better. There was some corrosion and rust inside and its all been gone through now and the armature cleaned up with emery cloth. I'm not going to pull the drive just yet.