fbh-velocity

HI, I live in Denmark and do a lot of boating. None in this country has ever heard about labbing props and nobody can do it. They can change the pitch a little up or down but as far as i understand in this forum that only change rpm not speed.

My boat is a Regal Velocity 23, 454 bravo 1, 1.5 ratio turning a standard mirage + rpm 5000- 5200. motor is around 500 hp
Speed is calculated in another forum to 77-78 GPS miles.
If I want aŽ labbed mirage 25+ can I expect some gain in speed at the same RPM? and if I witch, can they make it to turn 200 rpm more so I end up 5300-5400 RPM?

Boat weight is 4500 full tank 1 person

Anyone have a labbed 25+ mirage RH they want to sell cheap and ship to Denmark

throttleup

Typically lab finishing your propeller will increase the RPM about 250 and you should pick up about 2 MPH on top end. The important thng is to build a propeller that runs at the RPM at which your peak HP is produced.

Julie

fbh-velocity

That would be the perfekt situation, but you are right I need to know the peak HP. I just recived a desk top dyno 2000 program
this morning. I will try to calculate the powercurve. Have you any experience how accurate this program is or have you ever try to lab props due to the data of the program.?

I will post you the data as soon I finish them
What price range is new lab mirage 25?

fbh-velocity

Here is the desk top dyno result:

RPM HP TORQ

2000 175 460
2500 232 488
3000 290 507
3500 354 531
4000 417 548
4500 473 552
5000 511 537
5500 527 503
6000 511 447

As to the curve I think it Peak out 5200-5300 RPM
Maby I should Prop to 5200 RPM ? If I can trust the dyno test

bbladesprops

If the your numbers are accurate, I believe you to be correct in propping at 5300. If the 25 Mirage Plus turns 5000, Labbing it would be the next move.

throttleup

I would say that you should PROP FOR 5400 RPM at WOT. I believe that you said the 3B turns 5000-5200 RPM what is the pitch of this propeller? I would recommend that you rn the propeller agian and record the WOT RPM and post the data for us. We can then make a recommendation for you.

Julie

Pat McPherson

I have a good friend with a 1989 23' Regal Velocity.
His boat is powered by a modified 454 mag that makes about 400HP through Bravo 1 drive.
With a stock 25p Mirage plus the boat runs tops out at about 68-69mph (gps) @ 4800-4900rpm., but the boat does not come out of the hole and the prop blows out in some rpm ranges.
With a 14.5x25p Spinnelli 4 blade the boat runs about the same speed and the handling is a little better.
We also have tested a 24p Bravo 1 and a lab finished 26p Bravo 1. By far the best prop on the boat. The same top speed with the labbed 4 blade prop vs. the 3 blade and the overall handling is much better.
Don't waste your $$ on the 3 blade; buy a B1...

fbh-velocity

Nice to hear real experience. last year I was in the same power range as you describe. at that time my engine was aŽ duplicated 420 with a little more CR and headers. Same situation as you, very slow out of the hole and prop tend to blow out especially in turn. I went to 23 mirage + and did 5200 rpm and pretty good out of hole.
This year with the add HP it pulls the 25 mirage + out of hole very strong. Take immediately 3400 rpm when I hammer the throttle, makes a little work to come out and then accelerate very fast to 4900 then best trimming bring me to 5200 RPM 1 person 3/4 tank. It is still easy to make it blow out....
I will try a B1 24 next week, I can borrow one from a friend.

Did you feel any difference about purposing with B1? My velocity is tend purpose when trim out to best speed....

Pat McPherson

I believe you will find the boat will handle better all around and porpoise less as well...
Good Luck and Happy Boating.

fbh-velocity

I just try 22 Pitch B1. Perform very vell but took to many RPMs . Was more than 5800. Will try to find 24 pitch to borrow. I know it was too small but was the only one i could borrow right now.

How does a labbed prop work in bottom end?. Lets say engine turn to 3300 rpm full throttle, and make some work to plane with a stock 24 pitch. Will a 24 pitch Labbed prop turn to, lets say, 3500 rpm and then plane faster. Or is it only top end you gain RPMs ?