Wild Card 09

I ran my newest mod the other day. Adding to the 3" lift of the extension box, I swapped the standard length XR for a Imco 2" shorty lower. This brought the propeller shaft up to only 2 1/2" under the pad. I was hoping that by reducing the amount of drive in the water, I might find yet another mile.

But no! not a chance.

I tried three labbed Bravos - 28", 29" and 30" - and a labbed 26" Maximus.

On the first run with my old favorite 28" prop, I was encouraged by the fact that the boat came up only slightly slower on plane, with no slip or cavitation. The 525 actually doesn´t have much torque low down, so the additioinal grip that the noseconed shorty shape brings keeps everything hooked up, anyway.
Mid range was a little slower already, and I felt that the boat wouldn´t trim up and air out.
I was all over the revlimiter at 3/4 throttle, with 71 mph on the GPS.
I turned back to the dock thinking that the higer pitch was going to do it.

The 29" was no great help, and the 30" was even worse. The motor could hardly creep up from 1500 rpm, until we levelled off. Less revlimiter but no more speed.

The Maximus was better, and brought us up to 74 mph at just under the 5350 rpm. Still couldn´t trim the bow up. Essential for speed on a non-stepped Baja hull. The boat felt dull and boring to drive and was way below the speed I´m used to.

Time to go home. You can´t win them all, right?
I had a 1" spacer with me but the the day was turning cold.

When we get another warm weekend day, I´ll be back on the water with 3 1/2" prop to pad, and refreshed optimism.

tony stamis

it almost looks like the props half out of the water not sure but you would probably need a surface piercing prop to try something like that if they even make them for bravo setups

Perlmudder

awesome looking boat! love that paintjob, and the polished lower looks great!

tblrklakemo

Nice baja...you pulling it with a cayenne or a touareg?....hard to tell

socalstone

You are a wild man! Keep us posted, that is interesting stuff.
Did you buy the shorty or borrow it?
if you bought it and don't like it, I think I could find a new home for it.

empire0007

Mike wrote:
Hello Wild Card 09, i have a 33 OL that has the extention box on it, with the regular IMCO, planning on changing it to -2 IMCO shorties. After reading your post, did you loose speed or you gained some from it. Any advise from your experience??

Wild Card 09

As you can see on my signature, the best shot I´ve had was 81.2mph @5350 rpm using the stock DWP XR/labbed 28" Bravo. I could see 78 mph on the GPS whatever the conditions.
So with the shorty settup I´ve lost alot of speed, and the boat just feels dead, and unresponsive to trim. Like I said, the Baja hull needs to be running a little nose high to find its speed. The extension box made that happen, but raising the prop up so high has taken some of that leverage out of the settup.

I reckon that an Imco, Sportmaster or any sort of nosecone style drive casing doesn´t work efficiently when it is buried deep in the water. Getting the drive high, with the right (five or six blade surface prop, as has been suggested) should provide the power transmission from boat to water, whilst minimising the resistence. The problem is that Baja (non-step) hulls still need the leverage to lift the bow. I thought the Maximus would give me the grip to do that, but it didn´t.

By the way water pressure coming from the drive pickup was fine (2.6 bar @WOT) but dropped off radically if I trimmed out as far as I have been doing with the standard XR.
Although, I´m keen to find every mile that my 525 powered boat can deliver, I do want to finish this project with a useful powerboat and not a dragster.

With only a 26 foot boat, part of the fun is being able to handle not only water, but also situations that other more extreme boat concepts wouldn´t deal with so well.

Wild Card 09

Yes, I tow my boat with a Cayenne S. With good kit such as reversing camera and a towhitch that folds out at the touch of a button (only on the european versions), air suspension and the 4.8 liter V8, it is a great towcar.
Cayenne´s but also Touaregs, are becoming really popular amid the powerboat owners here. We trailer alot, and most people stay under 3.5 tonnes running single engined boats. Maybe because we pay over $9 for a gal of fuel, here!

Wild Card 09

Thought you might like this, Mike!

Yes I bought it, and will let you know if it needs a new home. At the moment it will probably see some test hours on various Bajas´s and Alex´s Pantera, before we are finished.

empire0007

Thanks for the info. Let me know how it turns out at the end. Love the paint job on it.