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Tinkerer 08-20-2016 10:06 PM

slip %
 
What is the typical slip % on a single engine cat?
I ran mine last Sunday and the slip was 3.8%

112 MPH , Bravo 28 ( used 27 ), 1.36 , 6100 RPM

Griff 08-21-2016 01:10 AM

3.8% is a very good number especially with a high propshaft like you have.

tmdog 08-21-2016 05:24 AM

Extraordinary. I'd frame those numbers.

billy boats 08-21-2016 09:19 AM

Almost seems too low to believe . Not saying you'd have a reason to lie, what I mean is that it seems like something is wrong in the calculations .
Is the prop stock or modified in any way ?
A stock 28 bravo prop use 27.3 for prop cal. If the prop has had cup added , or the blades trued then use 28
Are you SURE of the RPM? All 4 of my Livorsi tachs are 250-300 lower than actual

If indeed your numbers are correct your slip is 2% . I really don't think that is physically possible

MILD THUNDER 08-21-2016 12:42 PM


Originally Posted by billy boats (Post 4473295)
Almost seems too low to believe . Not saying you'd have a reason to lie, what I mean is that it seems like something is wrong in the calculations .
Is the prop stock or modified in any way ?
A stock 28 bravo prop use 27.3 for prop cal. If the prop has had cup added , or the blades trued then use 28
Are you SURE of the RPM? All 4 of my Livorsi tachs are 250-300 lower than actual

If indeed your numbers are correct your slip is 2% . I really don't think that is physically possible

I agree . I also noticed, that tach's aren't always 100% accurate, just like most electrical based gauges. Theres also the question of the GPS speedo accuracy these days. Seems like some are a little more optimistic than others.

I try to watch my chartplotter MPH when running for top speed. Its a little easier on a slower boat like mine I guess. Reason I do though, is I can watch the speedo going along, 83, 84.5, 86, 87.5, and so on, and watch them stabilize. Recall features are cool, but I have seen the GPS numbers spike 2-3, or more mph in a flash, which may not have been the actual number, but the recall shows it was.

Tinkerer 08-21-2016 05:17 PM

The tack is in sync with the EFI computer, The GPS speedo is in sync with the one on my phone, The prop is a bone stock BRAVO 28 and I used 27 in the calculation (the bell is cut off ),The drive is 1.34 or 1.36 ratio.
I have almost no drive in the water. Only the skag is in the water, the water is hitting the underside of the bullet at top speed. I find it hard to believe also.
This boat won't begin to get on plane without the mods I have done to the trim system.

Tinkerer 08-21-2016 05:28 PM

What are the slip #'s on a cat set up for racing???

abones 08-21-2016 07:41 PM


Originally Posted by Tinkerer (Post 4473373)
What are the slip #'s on a cat set up for racing???

I don't know what the race teams are running for slip #s, and I would assume that many race teams would not disclose that info. but whatever you have done to achieve these #s is quite impressive! Please keep us up to date on this. I'm sure you know the drive ratio is in either 1.36 or 1.34. I was thinking maybe a 1.25 but then your slip #s would be way high at 10%. whatever you are doing it is working! I would love have double your #s!

Tinkerer 08-21-2016 07:48 PM

The drive was built for me by Mr. Gadgets. ( Dick Tryce.)
When I went from a 1.5 ratio to the new drive ( 1.34 or 1.36 ) I lost 600 RPM and I believe that is normal RPM loss for that change.

abones 08-21-2016 08:10 PM

Yeah I have met Dick Tryce before. and is a hell of a great guy and drive builder! Like I said those are awesome slip #s.


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