zahndok

I'm interested in labbing my maximus 30 that I've had nearly 2 yrs. in the box. What would cutting off the diffuser ring theoretically achieve in addition to labbing. I have a 27 ft step bottom single with XR ITS and a modified 575sci to about 700 hp. I run a lab 32 bravo 1 currently with a 1 inch imco shorty. I only get about 83 wot. I've never been able to bring the slip down much below 21% with a bravo 1 prop of any pitch. I need to raise my top rpm on the maximus 500-600rpm at wot and perhaps get more bow lift as I tend to porpoise at 60-70 mph in smooth water with the bravo 1. Seems to require excessive trim to stop the porpoise.

Outdrive1

What did your boat run before the Imco shorty? Seems to me your x dim. might be high and that would cause your porpoising. Also if you can't carry your bow at that height it would also slow you down.

zahndok

Can't really compare as I had a stock 575sci before and changed in the first few hours to the shorty. Later came the power upgrade. The steering was much easier with the imco lower than with the xr lower. Even with the full hydraulic steering. I have thought of trying a spacer to compare. My concern was the boat rocked back and forth side to side with the xr lower accelerating to wot. Kind of a unstable feel.

bbladesprops

We cut the diffuser off on the majority of the Max props we do. It can reap as much as 2 mph gains. Most commonly you will get a 0-1 mph showing. There is the added benefit of decreasing the stern lift on surfacing applications, which is what you are looking for. We would suggest Labbing to a determined diameter and removing the diffuser to gain the rpm and attitude you need.

375stinger

if a boat is porpoising, and needs a lot of tab to keep the nose down...wouldnt that mean you want to reduce bow lift? im confused

bbladesprops

You need as much bow lift as is necessary to carry the boat comfortably and give the best performance.

Porpoising can be reduced by inducing the ability to carry the bow with prop changes, drive height, and CG changes.

If you use tab to control the porpoise and the speed stays up, leave it alone. If the tabs scrub a ton of speed, another option should be tried. Decreasing bow lift is a fine way to stop the porpoising as long as the bow doesn't stay glued. Decreasing the rake, adding blades, or raising the drive can stop the porpoise by raising the stern.

zahndok

Thanks for the info. I'm also tracking down a 1" spacer to try.

Brett, If the 1" spacer helps on the Bravo 1 would it likely have to come back off if using the maximus?

bbladesprops

It may not need to come out. The attitude of the boat will determine that. A lot of the time, a boat with a high X dimension will improve performance just by putting the larger diameter 5 blade on. Once the drive is dropped, the bigger propeller creates too much drag and stern lift to be tolerated. Because of your high slip%. You may be able to lower the drive and run the Maximus. I think that will be the case. Keep us informed!