GT, we all know the factors that affect pump RPM at any HP level, and know that any boat speed probably can be attained by a wide range of RPMs. Our PREFERENCE (not shouting, just emphasis) is to build torque motors and keep the pump RPM down. Since we do all of our engine and pump machining and assembly in house, it is easier for us to match the engine to the pump and vice versa, than most shops. I.E. Motor guy lies about the HP and pump guy has to cut or change the impeller or loosen the pump to get the engine in its power band.
One of my best friends is a retired pump/ flow engineer and we spend lots of time and research on this subject. As a matter of fact he is the Comp jet guy that runs the small block, I'm sure you know who he is. His engine would be more reliable, except his philosophy is to use the lightest, smallest, cheapest, (yes cheapest) part that will JUST do the job, like Pro-Comp rods, no chit!. The last race in point, one of his injectors failed (totally) early in the second heat, and he finished the last heats all on 7 cylinders. Too cheap to carry a spare, really. I believe he ran second and third in those later races. Usually he just splits the block or cylinders. Again the "anybody can build it strong enough, it takes an Engineer to make it JUST strong enough" philosophy.
Back to us. He keeps harping on the fact that pump efficiency relates to output pressure VS input pressure, and even before his input we made our pumps "tighter"(more efficient) than most, and that complements my preference for torque engines. Given the choice, I will always make my power at a lower RPM than most. We prefer the results: less wear, less noise, less fuel consumption at cruise, and less expensive components, because its not the HP that hurts parts, its the RPMs. All of our 70 and 80+ MPH boats run single carb, dual plane intake manifolds at under or around 5000 RPM. Its how we roll, been doing it for 40 years and have it down pretty well. We use single plane intakes to over 100 MPH, and haven't put a tunnel ram on anything in about 10-12 years, except for two guys that had them and liked the "look". They pay for that in fuel and know it. As an example I ran a 21 Daytona for 4 years with thru transom exhaust, swim platforms, pump in STOCK location, American Turbine aluminum "A" impeller (untouched, out of the box), single plane Merlin intake, single stock 1050, AFR 320 heads, Comp roller cam, 10.6 compression, REGULAR pump gas and no additives. 102 MPH RADAR and GPS at 5700 RPM. Dave (Aggressor) sent me a high helix "A" stainless impeller for evaluation when he first started making them and with no changes it dropped the RPM to 5500 and it only ran 96/97 MPH. Since it was cammed for 6200 RPM, I did what anybody would do, I stuck a bottle on it and it ran 6100 RPM in the 100teens. Still on regular. A ton of folks in Phoenix rode in it, it was only a lake boat, with a bimini top. I used to ride around with the top up and smoke a lot of boats that way. Me, a smartass, but prepared and anal(short for analyze) TIMINATOR
