Starter trouble question

Fellow CC owners, I've got a question about a little starter (boat starting) trouble I'm having. The issue relates to the starter not engaging (completely). First off, this boat has been mostly restored and now has electronic ignition.
What happens more and more frequently now is this: I turn the key, starter engages but sounds like it's not making tooth to tooth contact with the fly wheel, starter RPM's rev high with no load and then seem to catch (teeth) at the very end (as starter RPM's drop) making a horrible grinding noise. Occasionally this mis start doesn't happen and the boat starts on the first crank (new plugs, etc-etc). My engineering brain originally thought I may have missing teeth on the starter or flywheel. With the regularity of this problem, I now doubt it's the flywheel. It either seems like it's the gear teeth on the starter or some sort of engagement (solenoid) issue. Please let me know what any of you think? I was hoping to launch the boat this last weekend, but would like to have this issue resolved before I do. Hopefully this is something small as this boat has sucked every last dime from me (isn't that what a boat's supposed to do?).

Thanks fellow CC owners.
Big Jim

what engine is it ford, chevy? I would say a sticky solenoid and a chevy motor? if it's a ford then someting's not right, corrsion on contacts starter going out or weak battery.

It sounds as if the drive gear is not extending, not engough rotational speed to force it out all the way or if a GM stater the solenoid is bound up or bad not extending the drive gear completely all at once inticially.

What gauge battery cable are you using?

might want to pull the starter off and take a look at it, maybe even have it bench tested and see if the drive grear is actually extending fully all at once and not in stages. Might have some gunk or debrie in the nose housing preventing this. Only other issue it could be is a weak current supply to the starter, that could be a bad relay/or one on the way out, undersize cables, internally corroided cables will do it too, so if they are old might want to check them out as water can wick up from the ends and rot it out under the insulation where you can't see it.