Toffen

Hi,

The best prop so far has been a Merc Rev4 25 labbed by a local prop guru. The bowlift is better than Mirage Plus but less than Tempest. However, its faster than both. Top speed is 80 mph at 6,500 rpms and 1:1,75 gears.

This is with the prop tube stock. The tube is longer than other props, but is straight without a flare. I have been reccommended to cut it down with 16 millimeter. Some even cut it down with 25,4 millimeter (1 inch). 16 mm should give another mph on top.

If I am correct the shorter tube will give less transomlift / more bowlift. The question is, is there any down side shorten the tube? My boat is a straight V hull without steps and notch. You see the boat crusing and wot on these videos : http://vimeo.com/28897692

I will order a BBlades Blaster 4bl in the new year, but it would be great to squeeze an extra mile out of the Rev4 too

Happy New Year!

Cheeers, Toffen

A.O. Razor

Well, this is my take on it. If a 3 blade like the Tempest that provides you with better bow lift, will not yeld more top end, shortening the tube won't help. Why I'm saying this is because it sounds like the transom will sit too low in the water with the short tube. Granted, if people with the same exact setup as yours, are seeing speed increases with this mod, there might be something to it. No doubt non stepped boats love bow lift, but it is a balance thing. Too much is not good either.

Drikk nå ikke for mye av et hjem brent her for nyttår, i gale nordmennene Godt Nyttår fra Købanhavn

Griff

I highly doubt that you will see any difference cutting down the hub since it does not have a flaired diffuser ring.

Toffen

Hi!

Thanks. You have a point with the transomlift. It has to be taken into consideration. Maybe its better to add a little bowlift into the prop, instead of shorten the tube. Then we will have the same transomlift, and use less positive trim.

The prop was reworked for a stepped Airship 28 rib. My boat is a non step non noth hull from the 80-ties. No
added bowlift was added to the prop, just ability to be jacked high.

The easiest way to get more speed is to change to a standard 300 verado lower unit. The HD Poseidon is 5,44 dia vs 4,77 dia, and a few mph slower. But much stronger

Godt Nytt År!

Cheeers, Toffen

iammarcuse

I run a 25 Rev4 on a 21' Checkmate with a small stepped V hull and 250 Etec. It is also my best prop.
They cut down the Bravo One tube in order to make them into an XS for outboard use. They get more bow lift but the prop vents more on holeshot. On some outboards like an Etec with lots of low end torque the prop will blow out during break over. I assume a Rev4 would respond the same way. Personally I would not risk ruining the prop.
The Rev4 is one of the best kept secrets out there. Fast, smooth, great bow lift. The ideal prop for big horsepower outboards. It is too bad they never made them bigger than 25", then they would have a broader application.

Toffen

Hi!

Thanks I tend now to let it be. Wonder if the longer tube add drag, or its minimal. Its anyway less than a Bravo which has a flare in the end. I will ask the local prop curu if its any point to add a little more bowlift into the blades instead.

Cheers Toffen

bbladesprops

We developed the Revolution 4 in the late 1990's at plant 98. Then called the Mercury Marine Propeller Co. We intended it for 20 something foot slightly underpowered stern drives. At the time we didn't market it for other applications. When I started BBLADES we began using it across the board and especially on cnt console outboard applications with much success. It also became a great option on single and twin stern drives with true V bottoms. I have often lobbied for larger pitch options. However, since I'm no longer at Merc Racing, my opinion in that realm doesn't have the weight it once did. Actually, the prop people agree but the guys writing the checks feel a little different...............
I have written much over the years on this particular propeller. If you search this forum I'm sure you'll find more information than you want.

As far as adjusting the diffuser length, yeah it matters.
At BBLADES, we have various adjustments depending on the goal intended. Bow lift adjustments are options as well as stern lift changes. The amount of adjustment being made is specific and we have specs. for many variations. We have a variety of Labbing options as well.

On a selfish side, I prefer not to give those specifics on this forum. I guess I need to protect BBLADES to some extent since more and more of our techniques are attempting to be duplicated. I have been teaching folks for the last 8 years since this thread was begun by Steve and myself. BBLADES will of course continue to do so but in a more discrete manner.
Call me anytime and I can explain the process for the Rev 4 in detail.

Toffen

Hi!

Thanks Brett You are a true gentleman.

I will send you an email. I got this prop second hand, and I am ready to send it over to you for adjustment if you think its worthwile.

A Blaster will be ordered anyway. Thats next years experiment

Cheers and thanks, Toffen

bbladesprops

Always a pleasure Toffen. I always appreciate your patience with me email reponse times. LOL

I can't wait to hear how the Blaster runs on your hull too.

Brett

Toffen

Happy New Year! Good karma for higher speed cheers, Toffen