Prop Slip

[mlaagtho]

I run a Kevalcat 2400 with 07 suzuki Df140 with 24 pitch suzuki props(counter rot)
I have calculated the prop slip to be around 20%
I am thinking of changing to solas 4 blade 21 pitch props and would like to know if you guys out there have good numbers so I could work out the slip to see if is worth upgrading
From what I have read 5% to 7 %prop slip is OK
Thanks
Mike

[FNQCairns]

5 to 7% slip is not obtainable on your boat, those numbers are for light tinnys when flatout or decently powered fast boats when traveling fast enough to chine walk or there about's or those who's test numbers are rubbery somewhere.

Speaking of rubbery how good are your numbers? it doesn't take much to sway the slip figures, speed will have much to do with it as it is not constant, trim out will too.

If on your boat you see 12% feel happy very happy I suspect, 16 might be nice too. Slip doesnt not need to be a bad thing but if it is economy you are chasing via lower slip numbers the 4 blade will 99/100 times due to their less efficient design on slow boats such as yours simply swap a little less slip for overall less efficient propulsion so = no fuel saving, a mess after one considers the purchase price into the overall cost effectiveness.

Lost track this last few years but are not Suzuki props solas anyway.

[Spaniard_King]

I run a Kevalcat 2400 with 07 suzuki Df140 with 24 pitch suzuki props(counter rot)
I have calculated the prop slip to be around 20%
I am thinking of changing to solas 4 blade 21 pitch props and would like to know if you guys out there have good numbers so I could work out the slip to see if is worth upgrading
From what I have read 5% to 7 %prop slip is OK
Thanks
Mike

Why on earth do you have 24's on that boat setup.. it must be a dog to drive definitley go to something that gets your RPM up around 6000, I think 19s would be close

[finga]

Give Solas a call direct if your thinking about their props.
They'll be able to recommend something which will take a lot of guess work out of the equation.

[mlaagtho]

The wot is about 5800
When the motors where installed the motors where tested with 22 pitch and the WOT was 6100
In my wisdom I asked to have 24 pitch installed
The seas we run on are pretty flat so 24 are Ok The fuel consumption is 1to 1.1km per litre . The numbers I used are pretty acurate
4250 rpm 48 kpm 1.07 kph
3900 44 1.1
4219 47.8 1.08
This was with a nema 2000 connection to the fish finder and a gps speed
The read up on the four blade was better mid range econ
This equates to 20 % slip. Looking through other postings other owners seemed to be getting better numbers

[FNQCairns]

You could be right if distiled down to a cruising rpm, being the hull it is and given a 4 blades very narrow best performance range on our slow and heavy boats one particular model might cut the mustard, but feel assured it will fail in other RPM places for fuel efficiency, you can get some of that back by raising the engine/s higher than a 3 blade will usually tolerate... still physics is physics.

Just a couple of comments, you need more figures, preferably from 500-600rpm above plane then in 250rpm increments all the way to WOT and then graph them...worth the bother IMO for just the fuel for speed saving given a little time, for instance most state slip at WOT, then take whatever they get down further so be careful there.

More often than not user reports are pretty hopeless (so are official manufacturer reports - sometimes more so) but with user reports many covert the real reason for the incorrect numbers/outcome so extracting enough pertinent info is like pulling teeth, one first needs every time to guess which one of the many variables are the reason for the stated efficiency being too high or low...bottom line is whatever works for you in the end is the best choice.

there are more props around than just Zuk and Solas......I would run neither on my Zuk if I had one and I will own a 115 when the time comes, changed back to the old ratio..

Garry you might be thinking of the old gear ratio, i dunno.

[cormorant]

what diameter are the props? stainless / alloy? Running permatrims ? Calculate the slip through the rev range not just at WOT.
Nothing wrong with being slightly over WOT as extra weight in boats and then motors ageing and edge off props it comes back. Don't spend much time on wot anyway and slightly lower pitch will give a wider midrange when loaded. Yeah it may mean you use extra gas when in the high revs.

[mlaagtho]

the props on now are 14 inch 24 pitch stainless steel and have a susuki part # on them

[honda900]

mlaagtho,

These were all tested on my Yalta 555 with a DF140, I know its not the same but may be useful to you. Green is what I chose in the end as it wound up being the best allround for my hull.

Speed in kilometers per hour from GPS

Suzuki 13*21 - 3Blade Speed
1000 5.5
2000 10.3
3000 15.4
4000 33.3
WOT 59
Hole shot > 5 seconds

Turning point 14*21
1000 6.9
2000 11.8
3000 16.2
4000 38.5
5000 51.4
WOT - 5700 58.2
Hole shot > 5 seconds

Solas 13*19 - 4 blade -uncupped Speed
1000 6.4
2000 11.3
3000 16.4
4000 35.3
5000 48.2
WOT-6000 60
Hole shot 2.2

Solas 13 7/8 * 21
1000 6.5
2000 11.5
3000 16.5
4000 36
5000 52
WOT 5800 60.8
Hole shot > 5 seconds

Solas 13 7/8*19- 3 blade Speed
1000 6.5
2000 10.7
3000 15.3
4000 32.2
5000 45.7
WOT -61500 60.5
Hole shot 2.2

Solas 13*21 - 4 blade Speed
1000
2000 9.4
3000 13
4000 21
WOT N/A
Hole shot N/A

Solas 14 1/8 *18 - 4 blade Speed Fuel LPH
1000 6.8 1.4
2000 10.9 5.8
3000 16.4 11.4
4000 36.3 17.4
5000 49.6 26.8
WOT-6000 63.5 40.1
Hole shot 2

Regards
Honda.

[Spaniard_King]

You could be right if distiled down to a cruising rpm, being the hull it is and given a 4 blades very narrow best performance range on our slow and heavy boats one particular model might cut the mustard, but feel assured it will fail in other RPM places for fuel efficiency, you can get some of that back by raising the engine/s higher than a 3 blade will usually tolerate... still physics is physics.

Just a couple of comments, you need more figures, preferably from 500-600rpm above plane then in 250rpm increments all the way to WOT and then graph them...worth the bother IMO for just the fuel for speed saving given a little time, for instance most state slip at WOT, then take whatever they get down further so be careful there.

More often than not user reports are pretty hopeless (so are official manufacturer reports - sometimes more so) but with user reports many covert the real reason for the incorrect numbers/outcome so extracting enough pertinent info is like pulling teeth, one first needs every time to guess which one of the many variables are the reason for the stated efficiency being too high or low...bottom line is whatever works for you in the end is the best choice.

there are more props around than just Zuk and Solas......I would run neither on my Zuk if I had one and I will own a 115 when the time comes, changed back to the old ratio..

Garry you might be thinking of the old gear ratio, i dunno.

No Mate, talking from excperience. have a customer runing the same boat motor combo. 2007 models

[mlaagtho]

Hi
Thanks for the info
I will be changing out the props as the 24 pitch is to high, will have to do some more research as there appears to be no straight answer
Honda you mention in your test you can fit a 14 1/4 prop on the 140