Is 5% slip a decent number, or high??

[pwerwagn]

I was messing with my centurion tunnel this weekend with the ski prop on it. I have a 21" laser II that I use for ski-ing and stuff. My tach only goes to 6K rpm (which is about all it will turn anyways..).
According to the GPS, the boat runs 59.9 at 6K indicated by the tach. I realize the tach could be off a bit.

Figuring this, I got that with the 21", 6K and 60mph Im seeing like 4.9% slip. Is that good??
I got a 24 and a 26 chopper Im planning to put on it and going to raise the mota and hope to turn one of them 6K also to get more speed outta it.

--Jeff

[Ted Stryker]

5% is exceptional and typically only experianced with very well tuned prop and rig combo's... 10-15% is more average for the recreational boat/motor...

[Markus]

Slip numbers cannot be used like that, as most props don't have, say, 26.00 inch pitch across all blades.

[pwerwagn]

So what do you figure is off in my calculation? Is it most likely probable that the tach is a long ways off?



Slip numbers cannot be used like that, as most props don't have, say, 26.00 inch pitch across all blades

Im not really sure what you mean by that.

[chris_lacey]

I am also showing 60 at 6100 with a 21P Laserll. Maybe the 21 is actually a little more.

[RB in NM]

Hey Pwerwagn,

I did not see ya at the lake on Saturday, I was off the water at 11:45 due to the 12 noon weigh in. Sum prick in a Ranger with a PINK stripe tried to play chicken with us coming in to the main Marina,,it got a little western out there...:D
Fishin' sucked !
the Drinking part afterwards at Hotsprings got purdy good tho...

RB

[Markus]

So what do you figure is off in my calculation? Is it most likely probable that the tach is a long ways off?


Im not really sure what you mean by that.

Propellers are complex things. The pitch varies across the blade, and manufacturing differences mean that they differ from propeller to propeller. 21 inch pitch is not an exact estimate.

The most probable explanation is that the propeller's actual pitch is more than 21.00 inches.

[Jay R.]

The thing with slip calculators is that they are just that, they are calculators. use them as a tool to help you fine tune your set up. their is a good chance your prop isn;'t exact and your tach isn't exact. but its close enough that the numbers the calculator gives you are close enough to tell you where you are. like styker said 10-15 is average for a typical boat. boats like are are usually under 9 just because of the hull design alone. if you can get the numbers to pop up around 5 give or take your doing good, I have never seen anyone get lower than 4.

[pwerwagn]

Thanks guys. I guess I will just assume my tach is low by a few hundred and the laserII is effectively a higher pitch prop.
I understand where you're coming from now Markus. I was taking your comment a different way.
Maybe the 21 laser is cupped a lot or something.

Hey Russ,
where did you fish at?? I was on the south side of longpoint. I kept looking for you passing by, but never saw you.
My phone was no good down there, so I couldnt give ya a ring. We had some good drinkin at the dam site sat night...wish I coulda got a hold of ya.

--Jeff

[RB in NM]

I was going to head up toward Kettle Top, , on the way saw some whites busting the top. Shut down while I was in the bouyed boat lane (1/2 mile south of K.top),,,I was about 150 yards off the rocks on East side of lake, when I shut down my wake passed me up, it revealed a ridge of rocks 12 inches below surface ( top of a submerged ridge) that came out into the water 100 yards from shoreline ...:eek:
It was unmarked..... ! I was headed right for it... I fished there for a while then headed back to deeper water, down towards the Butte. My phone did not work either..

RB

[pwerwagn]

yeah, you gotta be careful at that lake now!!
wasnt it impressive how far it rose in two days though?? from the time I got down there wed night, to the time I left sun night, It came over 60' up the beach, prolly 5' or so vertically!!!

Oh well, i will be back down the 18th, 19th and 20th so maybe Ill catch ya then..

--Jeff

[MODXR6]

If you're saying all it'll turn is 6k (mota) & all you could turn a 21 was 6k then I doubt you're gunna be able to turn a 24 or 26 chopper to 6k. Unless you're running on the limiter at 6k w/ the laser. Chopper ain't gunna turn up like that thru hub laser.
Somebody correct me if I'm wrong but I just ain't seein it.

[RB in NM]

I waz kinda thinkin the same thing Mod,,,,kinda depends on the shaft height I think.
Pwerwagn, you got a low water pick up?

We have the next races down there the weekend of August 19-20. I have a couple of Soddy Daisy ET cuts, a 22 and a 24. I can bring em' if you want to try then out.
I do not know where we will be set up for this months race, probably still at the dirt dam area.

If'n yer down, swing on by. I have a little 'surprise' for the v-8 boys for the next few races......:D

If I don't break nuthin, I'll give ya a ride in the red XR-01. It's a light drag layup, but I have a second seat in her.

I need to take Linc up on the lunch wid' ya, but this week is busier than all get out.

Later, Russ

[pwerwagn]

No, it will turn the 21 more than 6K, but my tach stops at 6K so I dont want to just "guess" how much its turning.
I have a whole set of autometer marine series gauges coming with a 10K tach so I wont have to guess anymore.
It will turn the 24 6Krpm, but it takes forever to get it there.
the 26 will only turn like 5600 or so. so its definitley to big.

Russ,
No, aint got a low water pickup on this lower. Its a totally stock 88 200 fishin mota at the moment. I wanted to get all the bugs worked out before commencing mods (oil injection removed, carbs jetted close, etc). The lower also needs a new water pump, as all I get is like 11-12psi at 6K.
as far as I know I will still be down there on the 19th-20th. I'll find you. I may borrow those props from you next year to play with, Im not sure how much time I will have this weekend. thanks for the offer.
and yeah, if the red ally runs, I'll take a ride!!!!
Next week is fine for lunch too. no biggie man.

--Jeff