Need for Speed - Supercharging.

MIskier wrote:    I think the insinuation was that the MC 209 may have fallen into that category- that was a porpoiser, wasnt it?

The PS209 pulling footers from a FlyHigh can be a mess w/o properly distributed passengers. It also takes a couple hundred feet to plane out. Flat open water w/o load it's OK.

MIskier wrote: TRBenj wrote:    I think the insinuation was that the MC 209 may have fallen into that category- that was a porpoiser, wasnt it? None of the MC dd have had that problem, the 205v when weighted and the old x-30 with a step did have some problems with porpoising under certain loading conditions.

Are you 100% sure?

209 porpoising issue

TRBenj wrote: MIskier wrote: TRBenj wrote:    I think the insinuation was that the MC 209 may have fallen into that category- that was a porpoiser, wasnt it? None of the MC dd have had that problem, the 205v when weighted and the old x-30 with a step did have some problems with porpoising under certain loading conditions. Are you 100% sure? 209 porpoising issue

Yes under normal conditions i.e driving down the lake at high speed I don't know of any MC dd's that have had a problem. Some of the first 209's may have been more sensitive to it because like the first 197's they didn't have as large a hook at the transom as later boats.

TRBenj wrote: MIskier wrote: Yes under normal conditions i.e driving down the lake at high speed I don't know of any MC dd's that have had a problem. Click the link (above), become enlightened.

OHH so enlightened one I mentioned the hook issue in the above post.

"Some of the first 209's may have been more sensitive to it because like the first 197's they didn't have as large a hook at the transom as later boats."

That issue occurred with large amounts of weight towards the transom, which did occur on boats that were empty but had been optioned with the large motors L-18.

Hence the added hook after the '03 model year, which again was mentioned in an earlier statement.

Yeah!

Ok, enough 209 talk. That hull sucks anyway.

peter1234 wrote: i wish mine would porpoise . Mine just does half a porpoise

Is this half a porpoise?

Fast hulls vs safe hulls vs porpoising cannot really be separated from the water conditions and the hull design/driveline angle etc so it gets ugly but I will try to make a point in here somewhere.

It is clear that starting sometime in the early to mid sixties CC started to be concerned that bouncing was not considered desirable for the day to day boater. CC still in fact considers even light continuous bouncing at top speed to be a failure… I don’t know if they would allow bouncing that could be controlled by the hydrogate position although my guess is that even controllable bouncing is a cause for failure. I could tell you how I know it is a condition that they test for and that it is a failure but then I might not know things in the future so I won’t reveal my sources.   I don’t believe this to be a safety issue just a perceived ride quality issue… essentially something that needs to be prevented so internet geeks don’t talk crap about it and post links to old threads for decades to come.

In terms of speed generation and safety a little porpoising is helpful.. if it were to get excessive it would start to push back towards the less safe side in that it can lead to chine walking but that isn’t an issue with ski boats.   Ski boats are a special situation in that they need to get on plane quickly, keep the bow down for visibility, and keep the hull in contact with the water to allow a consistent and controlled shape wake as well as reliable tracking and excellent handling. A hook on the back of the hull along with forward to neutral weighting, relatively steep drive angle, and low rake prop design all serve the most important requirements of a ski boat.   

A fast boat needs different things… as little wetted area as possible, as much force as possible being transmitted in the direction opposite intended travel, and hopefully the ability to continue moving upright in the intended direction of travel under its highest possible speeds as it is likely to spend some time there.   If you were to look at jersey skiff some of the differences in terms of ski hull inboard to race hull inboard hit you over the head. A skiff puts a bunch of weight in the back and rides so bow high it is likely to bounce out the water at any given time… which sometimes it does. However, when it comes back down sometimes on its side it tends to keep moving forward.   This is good because if it went from 70 in one direction to facing in a perpendicular direction quickly the people would tend to stay in motion and the boat wouldn’t mind rolling over either.   A ski boat with flat bottom and a distinct chine has a great tendency to roll on its side should the back side slide out. The chine catches the water and provides a pivot point. A boat with a rounded chine has less to catch and simply rolls up on its side… the front to back lapstrake lines on the side of a skiff also end to channel that energy away from flipping the boat and more towards resuming forward motion.

Everything that makes a skiboat a good ski boat makes it a bad fast boat… the hook and drive angle, prop design, weight distribution all plant the nose which increases wetted area which requires more power for similar speeds. The planting nose is prone to catching cross waves taken at anything other than right angles, the steep sides ride across those cross waves providing a turning force that can only be countered by the rudder… however the planting nose also drives up the stern which in severe cases can cavitate the prop and rudder which increases the tendency for the rear end to slide out. The big fat foil shaped rudders that allow spectacular handling at skiing speeds are also prone to cavitation at higher speeds making them useless counteract the rolling/flipping action.

The fronts of these boats in general are an accident waiting to happen at speeds.   It is one thing to drive it down another all together to lift the boat off the water and ride on the nose. The under nose down operation the chines have a tendency when caught to try and spin the boat around due to their shape, when coming off a wake or riding down a wake if the boat rotates around its long axis towards the drive or passenger the keel line of the bow can do the same thing. If you are riding down into the trough of that wake nose down there is a good chance your stern is being lifted by it as well which will make your rudder about useless…

God forbid you overtake a big wake (heading in the same direction but not at a right angle) and you were to pull back on the throttle hitting the brakes jams down the nose breaks the rudder loose and the boat will roll definitely on its side… I call this the Green lake roll…

Word from Art Cozier was that the “spray rails” that look added onto the chines of a 1st gen nautique… were in fact added on and were found be required to keep that boat from occasionally hooking a chine and bow steering itself ATF. Looks like a story with legs to me based on my experiences driving these boats.   

The center fins don’t necessarily help cause instead of sliding out you can pivot around.   No real keel to keep you moving forward either on a flat bottom boat.

So if you want to make a sn or 16ft skier/mustang saferish at speed. First you get the nose up. Remove any hook, maybe even round up the back but be careful there without a clean cutoff.   Then move weight back (adding weight to the back works but is inefficient and can increase the danger should you plant a nose) .   This will make it worse ski boat and less fun to ride around in for those who don’t like a little bounce… (the wave also likely gets bigger and harder). Then you change out the rudder, move from a foil to a wedge shape, also increase the depth at which the rudder operates which cleans up the water it sees and also changes the balance of force on the rudder as a result of the prop wash loading. This will make the boat not handle as well at low speeds, not as big an issue for the 16 ft ers… again you aren’t helping the skiability.   Then you use a prop that has higher rake to help lift the bow… again worse skiing but faster and safer. Also if you are looking for a more efficient prop you could go to less blade area or less blades (2 maybe on a 16 footer) but that sure aint gonna help you hold speed against an aggressive skiers pull.

Should you do all these things and make your skiboat faster and relatively safer… I say start with a longer boat as you have a better chance of keeping it moving forward and a first gen with spray rails wouldn’t be a bad place to start… and still stay off the throttle on rough water.

Also consider lifejackets and kill switches as being helpful to those trying to help you after the scene of the crash.

Some may notice that my 83 has had none of these things done to it to make it safer at speed or infact faster. To the contrary all the weight has been moved forward with the tower/speakers/amps/batteries etc. What can I say I am not real smart. The one exception is that I use a prop that relative to the best skiing prop lifts the nose. If I put a 4 blade oj on it, it will ski better but I can within a day, on a wavy lake, hook a chine at relatively low speeds(55-56). Other than that I have chosen not to compromise its skiing characteristics, outside of reunions I do run a rev limiter on it.   However even at speeds in the low 40s with waves, all the weight in the front, and imprudent driving you can put one of these boats up on its side and make your passengers very uncomfortable.    On the other hand with flat water and a bunch of weight in the back I don’t mind running it fast until I feel the rudder break loose. It is simply not a great high speed boat but it is a ton of fun to bounce around in and to accelerate to, more reasonable speeds in reasonable water conditions.

Deep V boats have a number of benefits in terms of safety at speed. They tend to life the whole boat up rather than just put down the bow due to front to back lifting and sister strakes. The rudder tends to be deeper due to the v, the center of gravity is lower relative to the chines and therefore doesn’t induce rolling as easy, the chines are farther off the water the v keeps the boat moving in the right direction as well as reduces the bounce off the wave to a gradual effort .. there are fore to aft strakes that keep the boat from sliding around yadda yadda.

Even “flat bottom” vdrives have considerable differences to ski boats that make them both easier to achieve and safely live through high speeds.. not the least of which are more gradual front over hangs, significantly different weight distribution, different chines/strakes, different driveline angles, and prop/rudder differences. But they are still not ideal rough water boats at speed as they also can recover badly in significant cross chop.   

There are other non skiing optimized CC’s like the classic, barracuda, grand prix etc that I don’t have a lot of experience with so some of these rules and tendencies may not apply and certainly later model SN’s have got a little more going on in terms of hull design than a couple flat planes, abrupt chines, and flat sides.

Though of the day… Have fun, but try not to die.

Some good points Joe! Bottom line is and I have pointed it out before that these ski Nautiques are not designed to go much faster than they will or would have from day one. Yes their have been a few exceptions Bill Burgess comes to mind but keep in mind also he is a very succesfull runabout racer and has a very broad background in both building and driving fast runabouts. Our own supercharged program at Nautiques The boat's were propped for limited speed and all way's under the supervision of either myself or a corporate Representative.
Concern is safety from the start. The running gear in these boats can be pushing their limitations going up around the 475 hp range. moast V-drives that run inxs of 500 HP have prop shaft releases and utilize Steel for their under water gear,including Steel Props.
So If you want to go fast on a budget leave the old Bessy alone and pick yourself up one of these!


I have two!!

Great post Joe, and Jody your points really cut to the core of this - a fast ski boat is fun, but trying to push the limits too far really is putting the sqare peg in a round hole, at the cost of safety.

My jet boat is a mild 454 capable of 60 mph. With the pedal to the floor going 60 you can drive pretty casually (except for the wind with no windshield!), handles and turns nearly perfectly, only issue is not to launch it if larger wakes are hit as jet boats want to swap ends if you lose water contact for long or lose engine power. Add 200 HP and it will go 75 with the same excellent handling. It's made for it, but it's a lousy ski boat.

I'd think everyone here has driven an I/O into the 50's, most basic family I/O's will hit 50 plus these days. They handle so well in all reasonable conditions, hitting wakes at an angle won't do much more than give you a little bump. They're made for it, but are lousy ski boats.

So, seems to me that a 50-55 mph Mustang or Gen 1 Nautique is a really fun project, one I'd like to tackle some day, but that would be it, no need (for me anyway) to push beyond that.

Joe,
How close to getting that book you're writing getting to publication? I want one! Fantastic write up!

Got bow lift? yippee

MIskier wrote: Matt, I am going to have to vehemently disagree with you about the eco-boost engine being a marketing gimmick! Forced induction motors do offer greater efficiency just based on the thermodynamic characteristics of the engine setup versus a n.a engine.

That's cool...but remember, economy and efficiency are two different things.

Ford is/was selling the Ecoboost (stupid name BTW...TwinForce is much better) on economy...not efficiency. They said 20% better fuel economy...and in every single application of Ecoboost...it hasn't come close...and in the case of the Taurus/Lincoln Taurus...it gets WORSE mileage than a competitor's V8.

For the price of entry ($700-4,000+) Ecoboost is most certainly a gimmick.

Had Ford done something right for a change, they would have sold the 3.5 TT engine as an alternative to a small diesel. Then it would have actually lived up to the hype.

I mean...come one...it makes no sense that:
A. The 5.0 does not come with the same granny gear as the Ecoboost.
B. The 5.0 is less capable than the 5.4 which was a boat anchor (310HP).

Those two things make it clear that Ford is intentionally hurting the 5.0s performance to make the Ecoboost look better.

And remember, the Ecoboost mileage figures are from the 3.15 rear gear. Automakers are only required to test one rear gear combination for an engine. They keep the actual figures of the higher gears a secret (as they know the mileage will be far less).

And "Ecoboost" technology is not new...GM has had it for years.

It's all about the marketing. Ford can successfully market a V6 that gets V8 mileage. Good for them (or their ad agency).

Even with that pic you can see the difference in the huge front overhang and chines that run to the front rather than curve abruptly into the keel line just above water level.   Fun boats to acquire once your skiing needs are covered!

I mean...come one...it makes no sense that:
A. The 5.0 does not come with the same granny gear as the Ecoboost.
B. The 5.0 is less capable than the 5.4 which was a boat anchor (310HP).

Those two things make it clear that Ford is intentionally hurting the 5.0s performance to make the Ecoboost look better.

I hope they keep hurting the performance like they have been doing. For 2012 the Mustang has the same 302 cubic inch 32 valve V8 that puts out 412 HP and 390 lb-ft of torque while returning a very economical 25 MPG on the highway.
Puts a different perspective on 302/351 boat engines. What do they make, 200-250hp? Keep hurting that performance!

And "Ecoboost" technology is not new...GM has had it for years.
What ?