RE: What is a good speed? ? ? ? ? ?
I'd follow what Old Slow has to say. Getting your prop in shape and trying a few others is also an easy and cheap way to expiriment and possibly gain a few mph. I don't know anything exactly on those motors (Fuji?), but switching from a canister to a tuned pipe exhaust has given us 5-6mph on two different boats. I don't know if your exhaust spacing would line up with a homelite, if so you could use their manifolds. I'd personally just watch getting too deep into modding that motor and sinking a ton of money to get you 8mph, when new Zenoah 260's come up on ebay in the $200-$220/shipped range almost every day.
I'd love to see it go with a stock 260, even with the canister![X(]
Good luck,
Dennis