I'm about to start dialing in my newly repowered American Offshore 2600 and was wondering if anyone has done any prop testing on the same or a similar hull.
The motor (a Pro-Charged 509) should put out between 800 - 900 FWHP when it's dialed in and I'm shooting for a 110+MPH top speed.
I have an Imco Extreme 2" shorter Lower, 1.34 gears and no set back box. I currently have a 32" Bravo 1 (stock) which I want to lab but I wanted some feedback on that vs. say a labbed Maximus/ PX-5. From what testing I had done with the old engine combo, I could tell that the bravo doesn't generate much bow lift at all with the shorter L/U, so I'm thinking that there could be some top-end gain from having an extra blade. I'm also interested in acceleration comparisions.
Also, I note that all of the Merc props have a "bell-flare" at the tail-end of the hub and I wondered if anyone has seen any gains from cutting the same down or off altogether, especially on boats which have no exhaust flow through the hub.
Many Thanks for any information you may have.

Hardcore A/O,

Have you run a 5B on your boat....if so did you like it?

What are your performance numbers now? I am hesitant to remark on top end without knowing how well your boat is dialed in. Sometimes 5B propellers will increase top end but not always.

Julie

On your hull using the shorty. we have seen gains though out with the Maximus. Labbing the B1 may not be the best idea. It remains to be seen.

As far as the diffuser on the Maximus, yes it can net as much as 2mph. We cut them off often depending on the rig.

What rpm do you want to run the engine? Do you have rpm / speed #'s with the current engine and shorty set up?

We do offer test Maximus props when the time comes to begin testing.

I had a simular boat with less power. I ran an extension box on my setup. Most of the time, I ran my prop shaft 1/2" below the center pod. This gave me great bow lift with neutral trim and a standard bravo 1. I was never really happy with the prop slip and the bravo. Labbing would have helped, but I sold the boat before I had the chance. I did try some cleavers and found they would not carry the bow and would slip badly (but not blow out) on planing. The bravo 1 would not slip at all and planned better with the drive trimmed neutral than in. The diffuser ring should help hold the water on the prop and I fear you will get into prop slip/blow out with out it. I wouldn't be concerned if you had an extension box. Also with your power level, I don't think acceleration will be an issue. If you try to compare the acceleration between props you'll be comparining outdrives!

Thanks Guys.
I have no idea what the top speed is as yet, since I haven't run the boat since I re-installed the blower recently. I haven't tried a 5 blade as yet. I ran the new motor N/A with a 3 blade Houston-modified "Accelerator" Mirage, but the slip is excessive (like 16+%), whereas the same prop ran decent slip #'s (llike <13%) with my old stock lower unit and my old N/A (575hp) power. With my old blown combo @ 5lbs of boost I could swing a 34" pitch Teague labbed B-1 pretty easily (104 MPH on GPS before the motor ran out of fuel - due to inadequate fuel flow) with 1.34 gears and the stock lower. With the stock X-dim. the 34" B-1 gave me lots of bow lift. I also pretty quickly (second outing) snapped the prop shaft off, launching on to plane (trying to get out of the way of a bigger boat) and sent my 34 B-1 to Davie Jones locker!
So, all I currently know is that the boat should run around 108 - 110 with the new motor and with the elevated propshaft and I do believe that a 5 blade round ear will the hot ticket on this setup. I will report back with testing results after the weekend (weather permitting). I want to run the motor at about 5600-5800 RPM max, with 8-10lbs of boost, so I am also concerned about blade integrity with my level of power.
BTW: has anybody done any comparisions with the new Hydromotive round ear 5 Blade vs. the stock/labbed Maximius? Particularly on a setup similar to mine? I'm thinking that a labbed Maximus with the diffuser cut off is the way I need to go, since I 've had a bad experience with a Hydromotive slinging half a blade off.
Cord: Thanks for the tip, I know what you mean, I've already broken enough parts, trust me! I've also run a couple of "cleavers" on my boat and they handle like crap! Ditto for the Hydromotive 4 blade "cleaper".
Thanks again for your help guys.

I think you should first see what the boat does with the 32 Bravo 1 you already have. If it doesn't carry the bow a 5 blade is going to be worse.

The 32 should give you a good baseline to start with. Then, depending on what number you get go from there.

Matt

Matt:
I thought that most people were of the view that a running 5-blade at an elevated X-dimension actually generated MORE bow lift. Are you saying that a Maximus will have less bow lift than a Bravo 1 on my boat?

OK, this is a multi faceted question and answer.

First, the bottom line is.........more blades, more diameter, the more the propeller seeks the surface therefore creating less bow lift and more stern lift. I remember very clearly last summer on this board discussing with certain persons that the P5X was actually a stern lifting propeller. These people told me the P5X carried the bow on Bajas. Now I see the same folks suggesting the P5X and Maximus props are stern lifting propellers. We all agree now.

Each application is different though. That is why you can suggest theory, but need to look beyond the basics. On your application raising the drive will indeed raise the slip %. A Maximus or P5X will decrease the slip and increase the efficiency due to the diameter and length between load and unload of water. In other words it will work better than the Bravo 1. Is it a band aid? Maybe. Would the boat run better with a 4bl stuck 1" deeper with a spacer and without the shorty? Maybe. With your current #'s, raising the drive and using the B1 would be a back wards move. However I believe the overall performance of your particular application will be similar with either set up and this one will ultimately be the better of the two. The hope is less drag from the out drive and 5 blades to pick up the slack. You stated the B1 carried the bow at the old X dimention, with the raised height, the 5bl may be your only option. You also have HP vs. weight on your side.

Remember, bow lift is created by 2 things, hulls that fly themselves at speed and leveraging the stern.

Huh?

What do you mean Huh?

The larger the diameter, or the more blades you have, the more stern lift that is created.