DW

Cylinder Heads: GM Fast Burn 385 units. Exhaust Manifolds: Stainless Marine Small Block Aluminum Manifolds (they have actual primary tubes). Intake Manifold: Edelbrock Performer RPM. Rest of exhaust home made to match the 4" elbow exit, H pipe added, slip in stainless baffles from CP Performance, 4" stainless tips. Alternate sources for exhaust manifolds are Hardin or IMCO. Bassett makes a real set of stainless tube marine headers. Numerous suppliers make aftermarket performance GM manifolds. If a Ford, the GT40 route is the performance route to take. Power upgrade: Fast burn 385 heads (swirl, port flow, bigger valves), 10:1 compression ratio, ZZ4 camshaft, 1.6 rockers, timing remapped, blueprinted carb, 4" exhaust w/ H pipe, cold air induction, 160 stat. Will pull 5600 rpm in cool weather at 54-55 mph and idles great, biggest diff is the accel from 2-4500 rpm and all on regular fuel, 1:1 trans ratio w/ 13x12 Acme prop (I reworked and added cup). Small engine power, I would go either super or turbo charged since you would be fighting lack of torque on most of those units. The old Sanger, if think it was called Twister, was supercharged and could pull 70 mph but that was a small block Chevy also. That would have been a heck of a jump boat.

Aluminum cylinder heads are 50# lighter per pair, aluminum exhaust manifolds are 90# lighter per pair and an aluminum intake is 25# lighter. Add those up along with options on the engine water pump (removed) and misc. brackets and you can slice off around 200# pretty quick. It makes a noticable difference at least in my case. I am sitting at 250# in mass reduction at present. I don't run a closed cooling system in a midwestern fresh water lake and have not had any problems, salt or brackish water would be a different challenge. I have 4 zinc plugs in the system to act as the sacrificial metal and have accumulated over 700 hours on most of the parts in question all still in great shape. The additional 100 hp is a fun result as well which included some other mods as well so I can easily surprise that annoying jet ski that thought they were going to escape, plus it makes for a great footing boat. There are cf con rods, or the traditional carillo titanium rods are about as good as it gets. A more traditional approach would be to go through and cut weight out of the pistons and rods then balance the crank to suit and leave a pile of shavings on the floor. Lots of effort for not a lot of return in this case since acceleration at that level is not really a huge concern. There are aluminum blocks available as replacement items and of course the LS series of engines is all aluminum and much lighter.

I have always done it with the engine just fired up and cold, not fully warmed up and hot. Propane torch is a better alternative. Soounds like that is not an issue based on latest feedback.

Bruce, Have you confirmed that the boat has the same characteristic when not using PP? Has Michigan Motorz ever supplied a ski boat setup before? That would be a good question for them, and if not, what criteria did they use to set it up? A carb is not a "smart" item, it simply mixes an amount of fuel depending on how much air is passing by the venturi or more specifically, by how much air pressure depression is in the venturi. Add a little extra for fast throttle openings (accelerator pump) and there you go.

Bruce, Sorry to hear things did not go well. There are actually 9 screws to remove, I have attached an Edelbrock diagram, see item 16 & 17 on the breakdown. It sounds a lot like an air leak, your description of the characteristics would suggest that, add fuel and it runs better along with a surging problem. I assume you have checked to make sure a Marine calibration is in the carb, they are a bit different than a standard vehicle calibration. Edelbrock should have a spec sheet to help you on that. I would certainly be checking for an air leak, a spray can of starting fluid or brake clean can help you isolate the location of the leak.

Jeff Smith of Silver Spray Sports in Fenton, Michigan has equipped his ski lake with a lighting system, you might want to contact him and discuss. Any local race track will also have a lighting system for night races. Musco is a common supplier for lighting systems.

There is a perfect example of: "old age, treachery and experience will succeed over youth and enthusiasm". Nice work JTH, Mark Martin and Paul Newman would be proud. Too bad that S turn speed scrubbing trick doesn't work so well in slalom!

There are two components to the story or thread here, one is simply total weight and the other is location. Reducing total weight certainly helps, and lets make the assumption for this that it is evenly done across the length of the boat or perhaps done at the engine (ie: LS v. LT engines were the LS has lots of aluminum and less weight). Pull a fair amount out and it is noticable, I have done that on my particular boat. Location, that is actually a simple teeter totter example, take some out of the back and the teeter totter raises the tail, reverse and the nose comes up, pivoting around the center of gravity, approximately near the pylon/engine. Most effective areas to best take advantage of this effect is at the very ends of the boat, so the platform or the running light at the front. That is also why fuel can be a noticible change considering there can be 180# (30 gals) of fuel on board one of these boats, since it is weight and at one end.   That is one of the reasons behind where the Infinity fuel tank was located (midship), keeping a constant balance. Eric also brings up a good point about pitching the boat making the propwash change, much like the jets on a sauna where angling them changes the water characteristics on or near the surface if aimed reasonably close.

Bruce, for the Edelbrock you are correct, a heavier spring will lift the needle sooner.Â

The volume change from the hole size difference is actually quite a bit, I assume that would be part or all of the difference. I wonder if the bubbler is actually reducing the negative pressure on the warped deadrise that these boats have when underway. It would be interesting to see if you could measure any pitch attitude difference.

Developing a response to change spreadsheet is a big help in making changes in the heat of battle. Nascar is a great example of constantly making changes to keep up with changing conditions and those that do it best win. You can also see where former great drivers can struggle if the "brains" behind making changes due to changing variables are not as adept as a previous crew chief or race engineer. To MS and JTH, you think messing with someones fin gives a rise, what do you think an endurance driver thinks when the prior driver leaves him a damp "present" in the seat when he hops in! Empty the drink bottle. . .

Bruce, your note brings up a couple of questions, 1. do you have the wedge plate mounted on top of the intake manifold to level the carb?  2. Is the accelerator pump (actuating arm on lf corner of carb) in the top hole (most aggressive)?  3. do you have any air leaks, it sounds like that is a potential issue. My boat has the Weber version of the carb and it is very responsive and there is no surging at all with a constant or even slightly changing throttle position. Correct on the pump, only one. You might look at the needle jet springs, accessed easily from the top of the carb, you can see them in the pdf I attached, item 4 listed as a metering rod kit but you can get the parts separately as Ken notes from Summitt. Make sure you have or use the lightest springs available, that will richen the mixture earlier or quicker. I read the anti Carter comments on this post, but quite honestly my particular boat is more responsive and just as smooth as any FI boat on the lake, although it is not stock but the fuel system is not a limiter. The only real complaint I have is the bimetallic spring on the choke is not quite matched so I have to adjust the choke twice a year for the cold and warm seasons, but that is no big deal.

There is some tape that has perforations in it available, I will have to scratch the brain to remember where (Pegasus comes to mind). The bottom of the fuel cell on a Cup car is not simply a piece of flat aluminum! Modena should be a blast, and you can go see where those red cars are made.

First, it's cool that 3M will be some sort of sponsor for the boat. Corporations displaying thier wares and technological prowess is a good thing and provides funds and products for competitors. The concept of the riblet film is to keep the flow laminar along the entire surface of the hull and to minimize surface friction. If you can't do that, one then trips it turbulent as soon as possible. Given how much effort is given to the surface shape and finish, it is the former condition they are aimed at. Once you have laminar flow, reducing skin friction is the goal and if you can do that by minimizing surface contact area the better.

Jack Travers has a school outside of Orlando.

Scott, Do you like the 9900 better than the 9700 and why? I assume you like the Goode better than the Strada55?

Bruce, attached is a Weber carb parts list and exploded view picture. As for surging from engaging the secondaries, you could change the prop pitch a bit to alter the engine speed and throttle position to move out of that range. The engagement point of the secondaries can also be changed by adjusting the linkage on a mechanical version, engine speed will do it for vacuum actuated secondaries. The common "fix" is to disconnect the secondaries as noted previously but then they won't open so top end performance will suffer.

What is the size of the floor section you are describing, I assume it is the panel that lifts up to gain access to the rudder/exhaust/steering. 33 lbs seems quite heavy. What constituted the replacement 4 lb section, just a carbon fiber panel insert? Could you post a pic of that or even both of them. Thx.

"The good news is I'm real close. I am optimistic the change I just made is the last one for this ski. Now if it will just stop raining so I can try it!! "  Remember, that next lotto ticket is going to win, and your next pull on the lever will spill all the cash out of the machine/vanillaforum/js/tinymce/jscripts/tiny_mce/plugins/emotions/images/smiley-tongue-out.gif

It is always fun to make an adjustment and cure a problem or make things better. Many times a problem is down to the skier, but there are problems that can be cured / helped (or made worse) with an adjustment to either boot position or fin/wing settings. There are people that can ski around a non perfect fin setting and some that either don't want to or have a hard time doing it. I personally, want to try to make sure my settings are as good as I can make them, so I tend to try to adjust for conditions or problems. You should track all of your changes and understand what every change will do for you so that when you encounter a problem or condition you have a good idea what direction to go to adjust for it or return to something that worked. I do agree, there is limited time to allocate to fin tuning for most people, so it is easy to go with what you have and deal with it.

What is the weight of the new platfrm and what was the former weight? What savings did you get from the foam floor?

You will notice the improvement, it is all about changing the pitch angle of the boat. Adding to the nose allows the weight to act on a longer moment arm. Reducing weight is always a good thing to do as it lifts the hull out of the water. You could add some hook to the transom to help some more at the shorter line lengths. Another option would be to add chine which is another way of lifting the hull out of the water.

My experince does not match Jody's experience, but mine is only a sample of size 3 different boats.

Yes, I have modified my carb. That engine comes with a Weber carb which is the same as the Edelbrock or is the same as a Carter AFB. The Weber carb actually has a three stage needle whereas the Edelbrock only a two stage. My first suggestion would be to verify which unit you actually have, the Weber will probably be painted black and there is a small Weber logo on the carb itself. One test I would run would be a secondary spring test, remove to see if that makes a difference, if so, the secondaries are trying to kick in right at the spot you are running (what speed/rpm are you running?). Weber parts are first class, so if that is the unit I would suggest keeping it that way but you can substitute some of the parts. Don't mix jets and metering kits as they go in sets and the combination determines the fuel curve. I would suggest a rebuild, the carbs tend to collect debris that plugs up the filters and sitting creates some debris in the bowls. Cleaning and a light refresh will cure many stumbling issues with the carb. Make sure the accelerator pump is fresh and clean, the inlet filter is clean, the bowls are free of debris and any passages are clear. The accelerator pump squirter probably wants to be on the maximum throw position (lever on top front  with multiple holes in it). I have modified my carb, but because I wanted too not had too. I have changed the accelerator pump squirter (richer), lightened the secondary air valve weights, changed some of the venturi parts, smoothed out the flow passages, basically blueprinted the carb and optimized it for performance. David Vizard has a good book as a reference on the Carter AFB carb with lots of good tips.

+1 TW, much better visual than I had in mind! No wonder the radar gun didn't work, too much distraction.