the triple suzi's and yams will be faster top end due to them being bigger engines in cubic capacity from the very start.

but with a bigger prop you'l go faster top end.
if you have a very fast pull away you could sacrifice a bit of that and go up 2 more inches in pitch for the top end your seeking.
but remember you'l lose the pull away and suffer big time if a friend comes along for the ride.

37mph is bloody fast for what you have it on anyway.
what speed gain did you get with the jackplate ?

post some pics.