The dry weight of the two engines is almost identical, in fact I think the C12 is a few lbs less than the QSM. At least, if you believe the literature each company publishes. I don't doubt the pricing diff.We suggest a Cummins QSM11 rated for 715 HP would achieve the speed you are looking. We have also put a C12 Caterpillar and that would also get the speed you are looking for just a much heavier and pricier engine.
You are lucky to be able to do that, for me to put a boat on a trailer have it towed to a scale and then towed to wherever is going to cost at least $400. You have no excuse not to weigh your boats for the owners.Usually when we weigh a boat it is for the massive sum of $0.00
The most we've ever spent is $5.00 to weigh a vessel on the trailer, then the empty trailer is weighed for no fee.
Not exactly a deal breaker as far as price goes