Virtually every high performance boat gets a little bit "loose" at the very limit. The reason is actually pretty simple. Although water provides buoyancy, it also induces drag. So to get every last mile per hour out of any hull, you're balancing leaving as little hull in the water (to reduce drag) with leaving enough in the water to provide forward thrust and not pointing the bow at the sky at the wrong time. There are many ways to reduce the amount of drag such as trimming up to force the bow up, adding steps to the hull to aerate (lubricate) it and raising the prop shaft height relative to the bottom. And that's just a few of them. But all performance boats maximize thrust and minimize drag to get every last MPH out of a given hull / power plant combination.

Why don't family boats feel as loose at the limit? That's a pretty simple product safety thing. One doesn't want Ma and Pa Kettle buying one of your family boats and complaining that it feels loose at 45 MPH - or worse yet flipping it over with the kids onboard. Then again, it's pretty hard to loosen any hull up at 45 MPH. But, I think you get my point.

I do remember one of the editors of the former Powerboat Magazine taking a ride in a Fountain factory race boat once. He was amazed how much faster it was than a similar "stock" boat. He was also amazed how much looser it felt than the stock boat. The reasons? Everything I mentioned above, plus a whole lot more power. I can tell you from personal experience that driving a true race boat - even one set up properly - is not something you just hop in and do. It takes years of practice. And even when you do get good at it, you're still balancing the boat on the edge of oblivion in many cases. But that's how you win races.

Speaking of power, adding bags of power is guaranteed to bring out some of the worst traits in any hull. Hulls that feel perfectly safe with 500 HP at 70 MPH can become almost totally unmanageable with 800 HP at 80 or 90 MPH. That's where knowledge of setup (adjusting many variables to make a boat handle differently) comes in very, very handy. In fact it's entirely possible that adding a few hundred HP to a given hull may make it virtually un-drivable without major changes to the setup of other components.

You mentioned one of the more common nasty traits of many performance v-bottoms at the limit - chine walking. Chine walk can be managed through a combination of reducing the amount of trim (which diminishes speed), adding some trim tab (which also scrubs off speed) or working the steering wheel to counteract it (actually the best thing to do.) If you add more power though, this is only going to become more pronounced.

So if you want to add more power to your hull, think long and hard about the possible side effects first. I have many friends who have screwed up perfectly good / great handling boats by adding humongous power to them. Most of them are actually still alive to tell you all about it. But what virtually all of them ended up doing was severely limiting the resale market and value of their boats. Oh, and the reliability went down the tubes too. Hope that helps.

Tom

That sounds right on. The "floatiness" is not chine walk and dropping the drive a bit should stabilize it if in rough water or if it just feels too loose. Different hulls react differently to more power. Some keep going faster while others develop bad handling traits or just hit a wall and won't go any faster. My hull has been proven to be predictable over 100 mph (mine runs very stable 80s). As mentioned, full hydraulic steering is worth every penny. It sounds to me like your boat is running pretty good!

Not necessarily..speed is a relative dynamic that changes everything...ten more mph may make it dangerous regardless of trim or tabs. There is a design limit for most hulls regardless of mechanical influences.

Think about this...I have been running boats in the ocean and on inland Lakes and rivers for 45+ years. Your boat pushing 80 MPH is faster than most of the World Champion Offshore Power Boats 30 years ago. i remember if you had something that ran 60 you were blisteringly fast!! now we have standard power factory production step hull deep vees that run 70+ easily with a full fuel load and 4 adults on board. I think that in it's self is amazing.

I think that needs a bit of qualification. I drove a bone stock Donzi 22 a few weeks ago that we delivered new in the early 2000's. It had a 502 Magnum with a Bravo drive and whatever 3 blade prop it was delivered with. Although I wouldn't call what it did near the limit (mid 60's) evil, it did get very queasy and didn't inspire a whole lot of confidence in me trying to wring any more MPH out of it. This is where "setup" comes in. Hydraulic steering would have been really nice, but the stock steering didn't have any play in it. I think a different prop and a shorter drive would have calmed it down a ton. Adding any more power to that particular hull with its current setup would lead to a real handful.

A lot is in the set-up. These hulls like a higher X (Imco shorty). Props have an effect too but a lot of us are running Bravo 1s. I know of an Ilmor 22 Classic that runs over 103. I know of two others that run low 90s. I know of another that runs at least mid 90s. Those are the ones I'm familiar with; There are lots more! When everything is dialed in and clicking these boats are a blast to drive. Oh....and when you drive your first Donzi Classic you can throw most of your boating experience out the window! Mine scared the hell out of me the first time out and that is when it only went 73. Now driving my boat is my second most favorite thing to do....

Moose, the bow dance you describe is normal and I'd bet that your hull could handle more power easily but you need to talk to other owners of that hull first.