Stern lifting prop

[jdjames]

Having a problem with to much bow lift. I was thinking of trying a hydrofoil but after reading here and on the Bateau forum about stern lifting props decided thats a better way to go.
My current prop is a 'Turning Point' 'Hustler' 10.75" x 12 pitch
-5500 rpm = 28.5 mph by gps
-2000 Yamaha 40 2 stroke (1.85 ratio and 4500 to 5500 rpm)
- Boat is a Bateau design FS17 but it's customized and heavy. Fully loaded it's around 1550#s.
The weight distribution is good when sitting still and loaded but the stern digs in when you start out. It does flatten out wide open and I can trim out some wide open, but when cruising it's bow high no matter what the trim.
If I go with a 'Solas Amita' 4 blade stern lifter should I keep 12" pitch since it's already at the max rpm's or drop to a 11"?
Or should I go with something else altogether?
I'd like to keep all the speed I can but cruising speed is more important than top speed.
Thanks

 

[Philster]

Re: Stern lifting prop

Read this article:

http://continuouswave.com/whaler/reference/prop3.html

 

[steelespike]

Re: Stern lifting prop

It is almost universal to drop an inch in pitch when going to the 4 blade.
I think it is a good plan.Sometimes you can raise the motor a little more
(vertically)with the 4 blade.The antivent(cavitation)plate just above the prop;
even with the bottom is considered a starting point.Raise it to a point just before venting becomes a problem.Test the 4 blade before any other changes.Under ideal conditions you could gain a mile or 2.

 

[hwsiii]

Re: Stern lifting prop

JD, you need to get the same 12" pitch in the Solas Amita and your maximum RPM will be almost the same as they are now. You will gain on your hole shot as well as acceleration throughout the entire RPM range. Your main problem of the bow lifting too high at take off will be gone and your normal running attitude will be at a lower angle than it is now.
You will also find that your cruising speeds can be lower than they are now as well as your load carrying capability will increase and the ride should be smoother because of the fourth blade on the prop. In rough water you will find that being able to plane at a lower speed will be very helpful, especially if you are caught in something like Cracker Larry was in that depression area off the Carolinas. My recommendation for Larry's other prop was going to be a 4 blade prop specifically for running in formed seas far from land. After you change props we will look at the possibility of raising the motor a notch, but I believe it is probably close right now.


H

 

[jdjames]

Re: Stern lifting prop

Thanks Everybody.

H,
That's what I was hoping to hear performance wise. Got a 12" on the way. Thanks .
My cavitation plate is about .25" above the bottom now and that's in the last hole so lets hope the height is good or it's fill, drill, fill and drill time if it needs to be higher.
WOW the adventures of Cracker Larry!


Philster,
Informative article. good to know it's not all black magic.

 

[Billfo]

Re: Stern lifting prop

This is the 3rd boat Ive used a Stingray "classic" tail 175 & 150hp bassboats & now my 135hp Lund. Im "MY OPINION", the tails do exactly what they claim. Minimize bow lift & help keep you up on plane at lower speeds and stops that porposing up & down. I see you have a 40hp motor, Stingray makes a "JR" model that I believe you would be very happy with dispite what prop you are using. There are other makes & models of these tails, but again, I only have experience with the Stingray classic version.**NOT THE RED WHITE & BLUE tail.. my friend put one on his 16' 40 hp Lund & did not notice any difference.. (I told him which one to get but he didnt listen) anyway the Classic is about 40-49 bucks..

Having a problem with to much bow lift. I was thinking of trying a hydrofoil but after reading here and on the Bateau forum about stern lifting props decided thats a better way to go.
My current prop is a 'Turning Point' 'Hustler' 10.75" x 12 pitch
-5500 rpm = 28.5 mph by gps
-2000 Yamaha 40 2 stroke (1.85 ratio and 4500 to 5500 rpm)
- Boat is a Bateau design FS17 but it's customized and heavy. Fully loaded it's around 1550#s.
The weight distribution is good when sitting still and loaded but the stern digs in when you start out. It does flatten out wide open and I can trim out some wide open, but when cruising it's bow high no matter what the trim.
If I go with a 'Solas Amita' 4 blade stern lifter should I keep 12" pitch since it's already at the max rpm's or drop to a 11"?
Or should I go with something else altogether?
I'd like to keep all the speed I can but cruising speed is more important than top speed.
Thanks

 

[Billfo]

Re: Stern lifting prop

I have only had 3 boats, but cant help thinking "fill, drill, fill and drill" is not the way to go..

Thanks Everybody.

H,
That's what I was hoping to hear performance wise. Got a 12" on the way. Thanks .
My cavitation plate is about .25" above the bottom now and that's in the last hole so lets hope the height is good or it's fill, drill, fill and drill time if it needs to be higher.
WOW the adventures of Cracker Larry!


Philster,
Informative article. good to know it's not all black magic.

 

[jdjames]

Re: Stern lifting prop

Bill,
Appreciate your experience with StingRay hydrofoils. I'll keep that in mind if i can't solve it with the right prop. Is the 'classic' the 'Xpi'?

hwsii has helped alot of folks with their prop selection. He knows his stuff. Hope he doesn't mind but here's a quote from the boat building forum;

A stern lifting prop is better than a hydrafoil simply beause it is an integral part of the motor and not an add on that is designed to overome the bow lift reated by the wrong prop on the wrong boat and an reate extra stresses to the antiventilation plate and they have been know to trip on themselves at times and ause the boat to slam the bow down very hard. They do lift the stern of the boat up, but at higher speeds they an atually reate enough drag to slow a boat down by 3 to 5 miles an hour.

Oh yea, his 'c' wasn't working on his keyboard.

To properly protect a wood core transom you should drill oversize, then fill with thickened epoxy, then drill the size needed. So to move a hole it's 'fill, drill, fill, drill.
Some drill and seal with silicon then are surprised a few years later by a rotten transom.

 

[walleyehed]

Re: Stern lifting prop

Before you guys get all worked up about Hydrofoils lets get the terminolgy straight.
There seems to be some confusion about the difference between "BOW-LIFT" and "BOW RISE"...these are NOT the same...they come from 2 different areas for 2 or more different reasons.
Now, I know there are a few folks here that have some good experience with the areas in question, but I'm going to add my 2 cents anyway...
There is ONE person on this forum that has tested more props than I have, some the same, some not the same. I've been asked by 3 different manufacturers to test their Hydrofoils and I have....extensively.
I've been ask to test tabs from 1 manufacturer that knew I was using another brand, and I did test them....extensively. I also now run them exclusively.
I have taken an 18ft aluminum Deep-V and transformed it into a 60mph boat (at cruise) with an old XP 150 'Rude-same as the std 200 with XP heads.
I have taken a friends 19ft Lund with a newer 150 and removed the Hydrofoil (from experience), raised the engine, added the correct style of prop and gained just shy of 10mph at the same RPM.
I've tested at least a few props from almost every manufacturer out there with the exception of a couple of true Race-Born corporations.
Now, lets discuss bow rise and bow-lift...
Bow rise occures at throttle up and is a result of hull design and speed...when we increase the HP we shorten the time the bow is "IN-THE-AIR". When we use a true "stern-lifting prop" we shorten the time as well, BUT when using a stern-lifting prop we lose BOW-LIFT, creating more wetted surface, drag and lower speed.
We can install a BOW-LIFTING prop and have about the same BOW RISE but when we are on plane this prop holds more of the Bow "UP" out and clean with LESS wetted surface, less drag and INCREASED speed.
Then we can throw in the "Over-all lifters", which in most cases perform quite well if you are willing to tweak just a "little bit". The Lund, Starcraft, Sylvan, Alumicraft, Crestliner, Tracker deep-V's...they all do well with this style of prop, in fact they do "best" with this style.
The Hydrofoil is (In the words of Dhadley and I have to agree) a TOOL that can "help" with a particular situation, but it may not "Fix" this situation, a Band-aid if you will.
Jdjames, the Hustler is NOT known for top-end speed, nor high cruise speed. It tends to pull hard but slip ratio is usually high.
This may sound like a funny question but what do you have to spend on a prop??? Is the budget a "major" issue? I'm talking the difference of 300 insted of 125-150$.

 

[Billfo]

Re: Stern lifting prop

After reading Walleyeheds reply.. I see that I am not cklear on your real issue. The Stingray will reduce the bow comming up ONLY under normal settings & operation. as Walleyehed says, its not going tof fix any problem with your set up "IF you even have a problem".. All bows come up when starting, btw, make sure your motor trimmed all the way down.
Pictured is the one I have & have used. on all my boats.Not the new & improved XPII. BUT if I could get another 10mph making some changes Ill throw the tail in the trash !

 

[walleyehed]

Re: Stern lifting prop

Billfo, send me a PM with this info; which set of holes are the top engine mount bolts in and what prop are you running with and what is your wide open throt RPM with a normal load?
Then add speed and state whether GPS or other.
7-8mph is normal...you can expect at least that.

 

[Billfo]

Re: Stern lifting prop

Just reading thru old threads & seen your reply. Sorry it took me so long to see it ! Do you know if the original posters issue was solved ? I do not have any excesive bow lift issues- the foil in my applications just make things smoother & I can always look over the bow on holeshot..but, if I have a set up issue & dont even know it- im open !!! Thanks..

I will provide you this info next time I go out. (I will be trying new stainless prop). Maybe you can tell me what you think.

Billfo, send me a PM with this info; which set of holes are the top engine mount bolts in and what prop are you running with and what is your wide open throt RPM with a normal load?
Then add speed and state whether GPS or other.
7-8mph is normal...you can expect at least that.