finding the right flatboat prop

[limitout]

I am looking for a replacement prop that will give me good stern lift and not bow rise, extra speed is always nice too


the Suzuki listed aluminum prop part number for my motor is: #58100-95393

the ss prop I have now is:
POWER TECH SRD3 PROPELLER 11.25" DIAMETER, 13 PITCH, 3 BLADES, RIGHT-HAND ROTATION, BEST ALL PURPOSE, SS PROP, 20 DEGREES RAKE - POLISHED FINISH ONLY

It can be seen here: http://www.ptprop.com/index.php?page...mart&Itemid=46

the motor I have is:

Suzuki df40 4-stroke long shaft (20")
gear ratio - 2.27
weight - 240 lbs.

more specs found here: https://www.perfprotech.com/blog/uncategorized/suzuki-df40-outboard-engine-specifications

the boat I have is:
Alweld 1548vv modified vee (shallow vee hull)
length - 15.0 ft.
width - 48"
weight - 300 lbs.

more details on the boat can be found here: Alweld Aluminum Boats - Jon Boats, Bass Boats, Bay Boats, Custom Boats

I have a bad bow rise issue (estimated 30* angle) that causes it to be like im climbing a hill to get going.


here are the speed and rpm numbersfor the boat:

first test condition: fully loaded boat with 2 batteries (one in bow storage), one full 6 gallon plastic portable gas tank, two tackle boxes and 4 rods, one ice chest and a 25lb. bag of ice, 2 people weighing 450 lbs. with one of them sitting on the bow deck to balance the load. test was done from idle on smooth protected saltwater (1" ripples no chop).

from idle:
rpm - mph
1000 - 2.8
1500 - 4.5
2000 - 5.6
2500 - 6.5
3000 - 7.6
3100-3200 started to lift out of water, took 3500 rpms to finally reach true plane and loses plane below 3500 rpm
3500 - 14.6
4000 - 17.9
4500 - 22.3
5000 - 25.1
5500 - 27.6
5600 - 27.8

from a dead stop the boat takes 5-6 seconds to plane off when fully loaded


second test condition: unloaded boat with 2 batteries (one in bow storage), one full 6 gallon plastic portable gas tank, 1 person weighing 230 lbs. in protected freshwater canal (no ripples no chop).

from idle:
rpm - mph
1000 - 3.1
1500 - 4.6
2000 - 5.6
2500 - 6.5
3000 - 7.9
3050-3100 started to lift out of water, still took 3500 rpms to finally reach true plane and loses plane below 3500 rpm
3500 - 16.5
4000 - 20.5
4500 - 23.5
5000 - 26.0
5500 - 28.0
5600 - 28.6

from a dead stop the boat takes 4-5 seconds to plane off when empty

you will notice the numbers for rpms 1500-3000 are exactly the same (given a small margin of error) because its hard trying to judge the needle position to determine exact rpms since i don't have a digital tach.

note: the 3500 rpm readings cant be trusted as completely accurate since at 3450 its is teetering on losing plane and at 3500 it planes off and rpms want to climb so I don't know if im off just a little on the rpms there but I did my best and think they are accurate.

a little added info I received from a Suzuki dealer is that "according to them" only Suzuki ss props will work best for speed and performance and no other props do as well. Suzuki ss props costs the same as all the other ss props but they are supposed to give you an average 2-3 mph more speed then any other prop you can buy out there.

he said the Suzuki ss props are actually made by solas but they are proprietary and no info is available about them from solas as far as design or rakes, but Suzuki ss props are the same price as solas ss props but suzuki ss props cannot be exchanged if you buy the wrong pitch yet the solas props can be exchanged. they also said the solas ss props wont perform as well as the Suzuki ss props so just finding the correct solas ss prop wont mean its going to need that same pitch in the Suzuki ss prop and they very often won't be the right prop if you try to do it that way.


can you tell me what is the correct ss prop I should be using for my flatboat based on the numbers above? and does this "Suzuki is best" stuff sound correct?

I am looking for a replacement prop that will give me good stern lift and not bow rise, extra speed is always nice too

 

[SkiDad]

Re: finding the right flatboat prop

i read your other thread - it got too deep for me so i left it - but since you have posted this info - i would say that you just have a limit on what your setup can do - you are running really well with that prop - if you want to try something i would try a 15p solas prop. You have to take some risk and just spend 100 bucks. if it doesn't work out you can always sell one of the props for 50 bucks. Nothing wrong with aluminum... my boat has 15p props - 1 Aluminum and 1 Stainless - i run better with the aluminum one.

Products

 

[limitout]

Re: finding the right flatboat prop

Nothing wrong with aluminum...

for my application (shallow salt water oyster beds) aluminum would last about 4 weeks (if you got lucky) before it was trashed, you just cant avoid getting into the mud and hitting a few oyster clumps no matter how carefull you are.

 

[SkiDad]

Re: finding the right flatboat prop

well they make the same props in Stainless - check out Solas's website or give them a call.

Prop Finder

 

[limitout]

Re: finding the right flatboat prop

if you want to try something i would try a 15p solas prop. You have to take some risk and just spend 100 bucks.

power tech is sold by solas but im not sure if its one of their styles of props or if they are just sold by them and I realize I will need to buy a prop to test it out but im not prepared to just buy blindly with no idea what the rake is on the prop I buy

most calculators say I need a 16p so I think that's my starting pitch but who can tell me the prop that has the correct rake for my boat? I don't want to be looking at the sky when I take off.

 

[smokeonthewater]

Re: finding the right flatboat prop

I would say that that "suzuki prop" bs is just that BS... acting like their prop that they don't make is a secret from even the company that builds em.... right....

 

[limitout]

Re: finding the right flatboat prop

I would say that that "suzuki prop" bs is just that BS... acting like their prop that they don't make is a secret from even the company that builds em.... right....

maybe I said it wrong, he said they aren't allowed to say anything about it like rake or cup size or anything like that so calling solas wont get me those details and Suzuki wont tell what they know. im still thinking like you it must be BS because how "special" can it really be?

 

[limitout]

Re: finding the right flatboat prop

any other suggestions for props?

keep in mind the pitch isn't the most important criteria I am worried about just yet, but having good stern lift is

 

[limitout]

Re: finding the right flatboat prop

you are running really well with that prop

maybe as far as speed goes but it bogs down on take off and has terrible bow lift issues, so im not running really well with this prop at all except where it comes to speed but I don't have any issues I cant live with
(heck i've been living with it like that for 11yrs now)

thank you for the links but they are still giving me the only choice to make is the pitch. by giving me no description at all about how the prop functions or the application (not motor) it best fits its just a blind pig in a poke purchase. by any chance, do you or anyone else know for a fact that those props give good stern lift or are designed to work on flat boats? the problem I have now is because I have a generic general all purpose prop

 

[smokeonthewater]

Re: finding the right flatboat prop

You have stated that your local shop will let you test props and we have explained to you what to look for..... You pick up the prop and look at it... you can plainly see if it is raked or not.... try half a dozen props and see which one works best for you .... there is no magic voodoo where we tell you the exact prop to choose.... If you couldn't test we could pick one but you are best testing until you find the perfect fit.... then next time someone has your exact boat and motor combo you will be able to tell em which one....

BTW while you seem to really want not to believe me but the other boat WILL need a different prop than this one... not that one won't work for both but the perfect prop for that boat will absolutely NOT be the perfect prop for this one...

You can speculate all you want about one foot of this same amount of that or more lift and minimal drag but the dynamics of the hulls are not going to be the same. weight distribution will not be the same etc... For example, the new boat may have a center of gravity that is further forward and may not require as much stern lift and being longer it MAY be less likely to porpoise. at the same time the increased length will increase drag... there are plenty of other possible differences

the difference MAY (though there is no guarantee)be very small... maybe less than a second difference time to plane or 1 mph top speed etc tho.... I guess it's about to be a moot issue as you should have the new one any day aye?

 

[limitout]

Re: finding the right flatboat prop

You have stated that your local shop will let you test props and we have explained to you what to look for..... You pick up the prop and look at it... you can plainly see if it is raked or not.... try half a dozen props and see which one works best for you .... there is no magic voodoo where we tell you the exact prop to choose.... If you couldn't test we could pick one but you are best testing until you find the perfect fit.... then next time someone has your exact boat and motor combo you will be able to tell em which one....

BTW while you seem to really want not to believe me but the other boat WILL need a different prop than this one... not that one won't work for both but the perfect prop for that boat will absolutely NOT be the perfect prop for this one...

You can speculate all you want about one foot of this same amount of that or more lift and minimal drag but the dynamics of the hulls are not going to be the same. weight distribution will not be the same etc... For example, the new boat may have a center of gravity that is further forward and may not require as much stern lift and being longer it MAY be less likely to porpoise. at the same time the increased length will increase drag... there are plenty of other possible differences

the difference MAY (though there is no guarantee)be very small... maybe less than a second difference time to plane or 1 mph top speed etc tho.... I guess it's about to be a moot issue as you should have the new one any day aye?

I guess im coming off wrong here but please no im not trying to dismiss what you said about the new boat but it was more in the form of dealing with what I had to work with at the time.

as for the loaner prop its not really a loaner its a buy one and you can swap out pitches if its wrong but you have to pick one and stick with it. lets take power tech since that's what the shop im getting the boat from has. I have to select the model number prop I want and that's mine, I can change pitches but not model props.

I appreciate all the help you are giving me, I really do but sometimes I try to turn things around in a way that make sense to me and I can get on two parallel thoughts in the same discussion and it can seam like im not listening when I have heard the point and turned it into a what if scenario to better understand the "why" of it.

so I was trying to get a suggestion for my boat and motor since I couldn't test the new boat yet. I did this in hopes of getting a prop "model/style" recommendation to use and figured I would just need the right pitch after that.

you make a good point that what I think as "just 4" wider" and "just 24" longer" and just 100 lbs. heavier" is not "just" as small a difference as I was thinking it would be. I was only thinking in terms of the extra surface area would make more lift and less drag to offset the extra weight but I see now how I am assuming way too much.

I guess it's about to be a moot issue as you should have the new one any day aye?

well last I heard from the guy it would be next Friday or the Monday after that but it will take me about another two to three weeks after that to get it fully rigged as im having some work done to it after I get it. im adding a storage box up front and having the sides and floors covered and my side console will need to be welded in place all before I start hooking up the wires steering and cables so that's part of the reason I was a little dismissive of the "just wait for the new boat" idea. but I realize how right you are and I cant do anything until the boat is ready and rigged to test it.

as my brother inlaw suggested it may turn out the prop I have works great on the new boat and until I test it I wont know so I shouldn't be stressing over it.

thanks for all your help guys, you taught me a lot

I will start a new thread with numbers tested with the new boat if it becomes necessary, god willing it will work ok

 

[hwsiii]

Re: finding the right flatboat prop

limit, " You are looking for a 0 degree rake prop for your boat, or even possibly a forward rake prop, to lift the stern higher, not the bow. When I have a chance I will run the numbers you have posted and give you a recommendation for the exact prop and manufacturer as well as the model. "

" well last I heard from the guy it would be next Friday or the Monday after that but it will take me about another two to three weeks after that to get it fully rigged as im having some work done to it after I get it. im adding a storage box up front and having the sides and floors covered and my side console will need to be welded in place all before I start hooking up the wires steering and cables so that's part of the reason I was a little dismissive of the "just wait for the new boat" idea. but I realize how right you are and I cant do anything until the boat is ready and rigged to test it. "

I keep forgetting that you are ordering a new boat, and until you test the new boat with your motor and do some test speeds and RPM's, after you have made all of the changes that you intend to do, it is a waste of time talking about ordering a new prop, just like Kevin keeps advising you.

H

 

[limitout]

Re: finding the right flatboat prop

it is a waste of time talking about ordering a new prop, just like Kevin keeps advising you.

H

ya I just kept clinging to this idea that the boats aren't that different so I didn't have to have the other boat to start making prop decisions. I wasn't going to buy it until I had the new boat ready so I was just trying to cheat and do the testing for it with this boat "assuming" the props for both boats would be the same if the motor was the same