10:71 and 572ci? Nothing mild about that dude. I build marine racing engines and rig boats for a living. I use bowties and merlins with out a second thought. I even had a blown 632 in my current jet now I am selling it and am on the downhill side of a MONSTER 705CI blower motor and I am using a merlin super block for the build up. As far as heat, jetboats actually have a problem building heat unless you put either a remote water valve to resrict water flow or use a thermostat kit. You won't have any heating problems. One more thing, Dart (as in dart cylinder heads) has come out with a block called a super M that is a completely redesigned block. I haven't had the opportunity to get ahold of one yet but they are suppose to be pretty stout. I believe they are similar in price to the merlin. LEt me know if i can help ya any furthur. PEACE