John/Jeff,
I also put out a massive wake at 10 knots, defined as what kids fishing in a skiff would say if I swamped them at that speed. I agree with Bob...Don't run a TC255 at speeds between 8.8-16.5 MPH (I'd say 20MPH @3000RPM, just where BoatTest found the maximum efficiency, which is always going to be the same as the minimum solid planing speed) . At 10 knots you're smack in the middle of the No Man's Zone transition between max displacement speed of, say, 8MPH and planing. You can't see it from the helm, but the stern will be way low in the water, water up over the level of the engine cowling seals (I don't know how but they seem to keep the water out of the engines even when they're 3 inches underwater ) and entire bracket underwater, all of which generates a huge wake even without Permatrims. Around here, Mississippi boat drivers would be yelling and throwing their empty beer cans at you. (They never seem to run low on them, though they run out of gas all the time). In my Regal monohull the wallowing, unstable feeling while in No Man's Zone was obvious, but the TomCat is very stable and stays pretty level climbing over the bow wave, even with the bracket and engines drowning. For me, the most challenging aspect of driving the TomCat is getting on and off plane and avoiding those speeds (and/or RPM's) between minimum wake displacement (7 MPH for me) and a good solid planing (20MPH for me). That's the reason for my advice to Jeff on this issue. I still can not tell if I'm in the transition zone just by 'feel' or the horizen or even the inclinometer, I have to see the huge wake or RPMs or GPS speed or get hit by beer cans. Again, the design is very forgiving of imperfect driving. Bob noted he ran Suzi's with much different gear ratios, props and pitch on a lift-kept boat without bottompaint.
Coming off plane too abruptly drowns the stern more than getting on plane does (I had Eileen drive so I could see it all) and for slowing off plane, throttling down by 50-100 RPM per second seems to work best for my boat (excluding emergencies of course). To get on plane from 6 MPH with full trim down, I advance the throttles quickly to 3100-3300 RPM, let it settle out for a few seconds, then trim up 1 bar every few seconds. RPM and speed will increase without any further throttle to 3400-3700RPM (4 bars on my Yamaha gauge). Too much trim will cause speed to stop increasing or even drop off and the noise of ventilation. RPM may increase in the frothy water but speed won't. You can add throttle or decrease trim then. Above 4000RPM fuel burn really starts to take off. Best cruise (most fuel efficient) is around 3000RPM for most all well designed trailer planing boats, including this one, whether single or twins, outboards or sterndrives, cats or monohulls. (I may not have convinced Bob of this yet). Of all the hundreds of past planing boat tests I've seen, 95% had best cruise at 3000RPM (a handful at 3500 RPM). NOT ONE AT UNDER 3000RPM. Well-designed planing hulls will start to try to climb out of the hole at 1500 RPM, pushing a wall of water to do so by 2500 RPM. It's a great boat and you're going to love it. Since you should spend under 30 seconds at 9-10 knots out of every 100 engine hours per year, your huge wake at that speed is no big deal. Take the permatrims off and try it, but don't be disappointed if you still swamp skiffs between 8.8-19mph and burn more fuel to boot than at 20MPH and 3000RPM (and with a much smaller wake at that speed). Stay under 6.5 mph for no wake zones.
I invite doubters to find any planing, prop-driven trailer boat report for which Best Cruise is not 3000 or 3500RPM and send me a link. It's physics, and power ratios, and stuff the engineers figured out years ago. There are no secrets in marine engines/engineering that haven't been discovered.
John, watch the bracket while someone else gets on plane at different speeds, you'll be impressed. Great Boat!
Happy boating, everyone!
John
