I did a quick search on the website here as well as Google and while I couldn't find the answer specifically for your boat, I did see that another member used 5" bolts on the lower section of the outboard for his boat. If it were me, I'd honestly just go to whatever local hardware shop/store that you have near you and get a couple bolts in each size from maybe 3" on up to 5.5", going up by half an inch each time. There's a great place around here called Tacoma Screw that specializes in hardware that is a much better quality than what you get at Lowes or Home Depot, and their employees actually know what they're talking about... go figure. I'd tell them what you've got, see what grade of bolt they recommend as well as if they recommend any particular coating on it, and then just buy two 3" bolts, two 3.50" bolts on up to again probably 5" or 5.5". Worst case scenario is that you have a few extra bolts laying around and you probably spend $20 on them, though maybe they'll take them back if they're unused? I'm guessing you'll likely want some 316 grade stainless steel bolts, but again I'm no expert on the matter. Perhaps someone else will come along here with a better answer for you, but 3" seems a bit small for an outboard bolt.