CIG3

I'd give Brett at BBlades a call there might be some work that can be done with your Mirage props to get you where you want to be. Brett knows his stuff and will steer you in the right direction. You would be amazed with what they can do with adding or removing diffusor rings and labbing.

http://bblades.com/
920-295-4435

Kalaazar

Much appreciated.

MDonziM

K - whats your drive setup? +1 on Brett, I bought my B1's from him. I also really liked the performance with Maximus 5blades in regard to slip but once again I had too much pitch and have not gotten the right size set.

viking60

Kalaazar,
I was studying you prop testing results and was interested that the Mirage 25p were the fastest even though they pulled your RPM down. Shows you engines have a good torque band. When you said it was a pain to get on plane, was it because they put too much load on it at that low of a speed, or did they slip a lot?
Thanks for the help, Einar

Kalaazar

Hi Einar,

The Mirage Plus propellers gave us the lowest slip and incredible acceleration in the mid range plus the highest top speed.

The problem was coming out onto the plane, as the bow came up the propellers simple lost all grip and went into full cavitation.

By using just a little tab and moving body weight forward plus very slow throttle opening we were able to nurse the boat up and out.

My Bravo 1 drives are set at X -2.5" which I am informed by Jeff Hall is an 1" higher than "Short circuit" plus an 1" closer on the centres.

I have now sent these propellers to a prop shop to have them re-worked to see if we can obtain more grip at the lower end.
Ian
PS
Have you read the Teague article about prop rotation " in or out" he too favours out turning, but it is down to both the boat and the individual setup in the end.

h2oboater

[ My Bravo 1 drives are set at X -2.5" which I am informed by Jeff Hall is an 1" higher than "Short circuit" plus an 1" closer on the centres. ]



Ian Short Circuit is on 33" centers, that's about as wide as I have ever seen on a Magnum. Here are some pic's I have posted before of S C transom.

Kalaazar

Thanks Mark, very useful.
Tomorrow Jeff will be here to both write my "busy list" for the winter months and help flush the motors etc.
We will take similar picture for reference, may be of some use for others at some time
KR
Ian

h2oboater

Here are a few more transom pic's for reference .. Ian keep Jeff busy, we don't want him getting rusty.

Kalaazar

Mark,
It`s now official, the Ice Man has run his steely eye over your pictures and SideWinders dimensions and the Bravo`s on SideWinder are ----------------------
An 1" further up and 1" closer together and as a result -------------------- We don`t know where we are.

Worst still although we have tried all of these prop options he ask " are they all stock or have they ever been worked?" so now the plan is to send them all to the prop shop to have them measured and then see what sense it all makes.

Right now I`m thinking, now we are applying logic and getting into the science of it all. So when do you want him back ? and I can get back to screwing

around in blissful ignorance of what it might be rather than what it is. Great guy though, make a fantastic bilge cleaner !!

MDonziM

Kalaazar,

You didn't respond to my previous post but I'll try to answer your question(s) again. First, if your drives are " 1" up and 1" closer together", your propshaft in relation to the bottom running surface of the hull is 1 3/16th" higher than Short Circuit if you have Bravo Drives, and I doubt this is accurate. So now the question is why? Every inch out from the hull centerline is equal to 7/16th" rise in the bottom, or better stated -7/16" shorter distance. X Dimension is the distance from the crankshaft down to the hull bottom on center. So, since the distance between the propshaft and the cranckshaft on a bravo drive is 21 13/16" an X-dimension of 16 13/16" for example will produce a propshaft 5" below the bottom. The distance between the crank and propshaft on a TRS drive is 23 1/4" to 1/2" (from recollection) so basically if you swap from TRS to Bravo your propshaft will be about 1 1/2" higher. The problem is the Bravo transom assembly is slightly smaller than the TRS so most people end up patching or replacing the transom (with engines removed) so you lose the exact crankshaft hole location. The TRS assembly is also taller from the top of the housing to the crankshaft which is why measuring from the top of the transom is useless when comparing to a Bravo installation. On a Bravo it is 9 7/8". This is why I asked what your setup is. Comparing measurements between TRS and Bravo installations with different centers or measuring from the radius below the rubrail to the transom assembly are all rough estimates at best.

In my application the crank C on C is 33 1/2" and my X-dimension is 17 1/4" so my propeller shaft is 4 9/16" below the bottom at center. The distance from the bottom at center to the bottom of the keel perpendicular is 6 3/8" so my propeller shafts are 1 13/16" above the bottom keel. With 550hp supercharged 454's and these dimensions I could not get on plane turning out a set of 3 blade props. Stock 4 blade 32" pitch Bravo 1 props work well, get on plane easily (2800rpm, no tabs) and nice cruise speed but have high slip #'s around 17-18%, Turning out made the boat bow steer and not track well, turning them in made a huge difference in all round handling. I really like two sets of Maximus props I have tried but both were too big. One set had the diameter cut down and 32" pitch, the other were stock 30's. Both sets brought the slip #'s down to 12-13% but I could only get to 4400 rpm or so. With my other project I haven't had a chance to test a set of 27's or so to get the right WOT rpm.

- Marshall