Prop Slip Numbers

[olmo40]

Im trying to work out some prop slip numbers for the new 4 strokes ,with all the hop up kits on the way ,Just cant get any calculators to work .The Suzuki has a 2.29.1 ratio,what im trying to do is work out at the say 6100limiter what prop for 90mph ??? ,Note im not too good with a computer

[pyro]

Prop calc here: http://www.rbbi.com/folders/prop/propcalc.htm

Are you sure about that gear ratio? Sounds a bit tall for a torquey 4-stroke.
You'd need a 40 pitch prop to get there with those gears!

[olmo40]

Thanks ,

When i plug in the numbers i get" NAN "

It works for my Merc stuff ok

Just got the ratio off the Suzuki spec page ?? will double check

[150aintenuff]

use mercury racings prop calculator its unlimited in its equasion... just leave 1 section blank

http://www.mercuryracing.com/propell...calculator.php


and fyi pyro... suzuki are an offset drive meaning their lowers are like a 1.87 ratio or perhaps even taller, but there is a second reduction below the powerhead that is around 1.2:1 or there abouts.. (never seen the actual tooth count) so overall it is yes a 2.24 or so gear would be about right (1.87*1.25) the gearing is what makes them torqey..... not the powerplant... put 2.3:1 high altitude 115 optimax (V6) gears in your bridgeport and see how torquey your engine becomes...

[olmo40]

I still get NAN .

My buddie gets 6omph from twin 250DF Suzuks of a 30ft Cat spinning ,16x21.5 Suzuki props @6100rpm.

I got to thinking over a beer or 2 and after reading Pyros post about happy to run 85mph these days most of the time due to family and safety etc.

I was just thinking about a 4 Stroke on my Venom and what size prop it would spin or i would need for 90mph ??

Probably wont do it tomorrow but one day

[pyro]

I still don't understand how a motor with an effective 2.25:1 gear ratio is going to run 90 mph at 6100 with ANY prop available.

[olmo40]

Im with you, just wanted to plug some numbers in to see what ,prop,slip etc to get a decent speed ,what has cracked my lately is the number of smaller boat im seeing with 4 strokes ,cruising around ,skiing etc .Not just the bigger OS boats i usually see.

[tj309]

I would not hang a 4 stroke on a Venom. I have a 500 lb 2 stroke motor on mine and with a full tank of gas it sits really low in the back.

I also agree with Pyro - no way can you hit 90 with a 2.25-1 ratio.

If you want I will post the formula to calculate speed and or slip if the prop calculators are not working for you.

[tj309]

A quick add to my post - Merc's 200 hp 4 cyl Verado weighs 510 lbs which a Venom could take. The 6 cyl models are 635 which IMO is too much weight for a Venom. The 4 cyl 200 would take you to 85 if rigged perfectly - based on what I have done with my 225XS. I do have a 40 lb hydraulic jack plate.

I don't know what the suzuki's weigh but I am sure they are close to the Mercs.

Also the Venom is not exactly what I would call a "family boat". They ride really nice with 2 average weight adults up front but with 4 aboard you will get one hell of a bow lift on take-off. On mine I jack down all the way and trim in all the way when 4 adults are aboard for takeoff which minimizes the TIME - not the bow lift - to get on plane. Once the bow comes down and my wife stops freaking I trim and jack for the ride.

[olmo40]

TJ , my wife wont even get in my Venon anymore and it only has 200hp at present ,Im just thinking about the future and been in a few 4 stroke boats lately ,which got me to thinking ,Suzuki has the best power to weight from memory thats why i was wondering how much prop it would take ,or if mercury will make bigger pitch props in the future,Pyro is right it would need to be 40 pitch or so .Lets see a 40 Chopper 2 with a bit of extra cupping thinks