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waterbum
12-13-2001, 07:40 PM
I have a 25'warlock cat that likes to porpoise on the top end. I have installed tunnel tab's,it helped but didn't cure the problem completely.Rough water no problem,calmer water the porpoise is worse. The problem starts at around 80m.p.h. I checked the last 6' of the sponsons and found a quarter inch hook most of it occuring in the last 8 or 9 inches toward the transom.A race tune on the prop also seemed to enhance the problem.Current speed at it's best with H.P.power,1.36 gear and 26 bravo 1 is 89m.p.h. on g.p.s. Will bluprinting help rid me of porpoise? You guy's are right, the folkes at warlock don't give a rat's ass about ANYTHING once you buy the boat. I experinced it first hand. Too bad they can't get their act together. Thank's for any help!

SVO 540
12-14-2001, 02:08 PM
Waterbum, I am not a bottom expert unless your talking chicks. If your bottom is OK I can give the following advise. I have found with my Mach 26 that it can develope a porpoise around 80 when in calm water, however I can take out the porpoise by adding more positive trim. I think the cause of the porpoise is the boat trying to get aired out but there is not enough speed (air under the tunnels) to carry and keep the nose of the boat up. Adding more positive trim helps to carry the nose so it doesn't drop back down, pack more air, lift the nose, drop back down and continue this cycle. The reason you hear of boats driving through this porpoise is because they achieve enough speed to carry the nose of the boat so it doesn't drop back down. I think if you had more power you could drive through it. Remember, when you add positive trim you may be restricting top speed. My Mach runs the big speed numbers between 0 and +1 trim, however sometimes I may be trimmed up to +3 or so to eliminate the porpoise we are discussing. Good luck.
By the way 89mph with HP 500 power is very good. What rpm were you turnning at this speed?
SVO 540 - OUT

waterbum
12-14-2001, 02:44 PM
Thanks for the reply. The boat turned this speed in very choppy conditions,r.p.m. was about 5150. My H.P. is slightly modified. Your right, positive trim stops the porpoise but affect's speed. Is it Procharger time?
[This message has been edited by waterbum (edited December 14, 2001).]

MrHavasuCat
12-17-2001, 11:30 AM
89 mph sounds a little fast for an hp 500. With your numbers that works out to 4% slip. Was this recorded on gps or radar?

waterbum
12-17-2001, 06:47 PM
G.P.S. Gaffrig said 92. My slip calcs may be wrong ,I figured 8%. 5150 x 27p x .735 x .00094697 = 96.7 - 8% =89.0 Boat only ran this speed once,haven't been able to duplicate.Usally runs right around 86. My h.p. has circ pump removed,replaced with Eickert crossover.Intake is fully ported,with 1" phenolic carb spacer.Carb is a stage v Nickerson Holly. Race tune on prop by Bronson Hill.

waterbum
12-17-2001, 06:57 PM
Originally posted by waterbum:
G.P.S. Gaffrig said 92. My slip calcs may be wrong ,I figured 8%. 5150 x 27p x .735 x .00094697 = 96.7 - 8% =89.0 Boat only ran this speed once,haven't been able to duplicate.Usally runs right around 86. My h.p. has circ pump removed,replaced with Eickert crossover.Intake is fully ported,with 1" phenolic carb spacer.Carb is a stage v Nickerson Holly. Race tune on prop by Bronson Hill.I must sound like just another hole lying about speed but I know there's to many knowledgeable dog's here to do that.

MIKEHTMSR24
12-17-2001, 08:16 PM
Here is a easy formula for slip
rpm x pitch
------------------------= speed w/o slip
1056 x gear ratio
speed w/o slip - actual speed/ speed w/o slip and then press the old % button.
5150 x 26---------133900 27 pitch =139050=96.82 mph
------------ === ------------=93.23 mph
1056 x 1.36----------1436
93.23 - 89 = 4.54%
96.82 - 89 = 8.08%
8 to 12 % is good for a recreational cat
4 to 8 % is good for a race tuned cat
Check out www.go-fast.com (http://www.go-fast.com)
They have lots of good info on their site
just plug in the numbers and it will tell you the rest.
[This message has been edited by MIKEHTMSR24 (edited December 19, 2001).]
[This message has been edited by MIKEHTMSR24 (edited December 19, 2001).]
[This message has been edited by MIKEHTMSR24 (edited December 19, 2001).]

Cole
12-17-2001, 08:20 PM
I have a really "DUMB ASS" question(jet boat owner and all)and trying to up grade!!What is prop slip!!!!

Havasu Hangin'
12-17-2001, 08:28 PM
Originally posted by Cole:
I have a really "DUMB ASS" question(jet boat owner and all)and trying to up grade!!What is prop slip!!!!
Theoretical speed vs. actual speed = prop slip
That lost speed is area for improvement. I like this slip calculator (http://boatpropellers.com/propcalc.html).
http://www.goldenplasma.f2s.com/forum/smilies/happy25.gif

waterbum
12-17-2001, 08:48 PM
Originally posted by MIKEHTMSR24:
Here is a easy formula for slip
rpm x pitch
Dude,my gear ratio is 1.36,Thanx

waterbum
12-17-2001, 09:11 PM
:confused http://free.***boat.net/ubb/biggrin.gifamn keep forgetin to change my face,sorry.

MrHavasuCat
12-18-2001, 03:45 PM
Waterbum,
With a 27" prop that works out to 8% which sounds more reasonable. I calculated your slip before with a 26" prop that I thought you said you were running. 8% is very good slip numbers. I guess 89 mph with the mods you stated you had on your hp sounds about right.

waterbum
12-18-2001, 06:20 PM
Thank's for the vote of confidance Mr. H-cat. Didn't want to get off on the wrong foot here by posting questionable numbers. Sure would like to make it to Havasu someday and hoist a truckload of silvers with everyone. Been threatnin to go to the ***boat mecca just haven't found the time. Besides,i'm draggin an ancher(the wife). I'm a hot boat man married to a cruiser queen. Hope she don't see this.

MrHavasuCat
12-19-2001, 11:08 AM
If you make it to Havasu you won't ever want to leave. Hope you can make it someday.