[jclark003]

I just got out of a 43 open with 3196 which is basically the same engines your C12. Pretty much had the same issue with slow rolling of the starters especially when cold. I paralleled every time thinking exactly as you, that all that current would be eating up the starters. Even with parallel and new batteries those things cranked out slow.

I'm guessing a little here but I think the issue relates to the electrical systems being configured at 12v instead of 24v. I dont think Cat offered 12v electrical on anything larger than the C12 so it's probably right on the edge of getting by.

By comparison my 3406 (C15) engines are 24V and instantly light with the touch of the key. No parallel needed. No dragging of the starter.

I would keep the batteries topped off, make it a habit to clean the terminals every season or two and get used to the two handed starting method. Great boat by the way.