Suggestions for the prop challenged

[WTodd]

Ok I am a prop idiot and I've searched but can't find an answer for my specific application; 2012 Lowe ST175, 60 Mercury. I believe this pic is about my current prop.

I'm not looking to necessarily go faster but my issue is sometimes I lose grip when getting on plane especially when following someone that just got on plane. Because I just don't know that much about props I'm looking for specifics so I can order a new one and put it on; yeah I'm good with mechanical stuff. I'll consider another aluminum one or a stainless steel one. The boat is for the most part stock EXCEPT I've added 2 Talons so there's about 75 more pounds back there now. Thanks in advance


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[Mike Cork]

Without knowing your RPM numbers it's hard to suggest a prop. But you said you're happy with it's performance other than the blow out.

My first recommendation is a stainless steel prop, the flex of the aluminum might be what's getting you. When getting on plane there is a lot of flex in the aluminum and it changes your pitch.

Look at your current prop size, then try a stainless steel prop that is one pitch lower. Sometimes you can run the same size but without the flex, it can be hard too.

Before you buy, ask your fishing community if you can borrow a stainless prop to try. I think you'll see a big difference. By borrowing one, you won't have to worry about what size to order, order the size that works best.

[WTodd]

Without knowing your RPM numbers it's hard to suggest a prop. But you said you're happy with it's performance other than the blow out.

My first recommendation is a stainless steel prop, the flex of the aluminum might be what's getting you. When getting on plane there is a lot of flex in the aluminum and it changes your pitch.

Look at your current prop size, then try a stainless steel prop that is one pitch lower. Sometimes you can run the same size but without the flex, it can be hard too.

Before you buy, ask your fishing community if you can borrow a stainless prop to try. I think you'll see a big difference. By borrowing one, you won't have to worry about what size to order, order the size that works best.

Thanks; I plan on going to my "boat guy" to see if 'borrowing' one is possible. In my research 1 aluminum prop that keeps coming up is the 4 blade Spitfire. I'm certainly considering a SS prop.


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[Mike the fox]

I can't remember where but I believe there is a borrow a prop website where you can try out a prop and if you don't damage it then you can return it if it doesn't work out.


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[Princeton_Man]

Mike is spot on. RPMs are an important clue. Aluminum is popular because of price and weight, but flex changes pitch and aluminum can be damaged easily.

You may not have a jackplate, but there's also a possibility of dropping the motor a bit to lower the prop shaft a little.

[Oldfart9999]

The cheapest way to do it is buy a "whaletail", they are easy to install and work great, they also help your holeshot. I've used the Sting Ray Classic with very good results, a friend had a Hydro Sport with a 150 on it, chine walk monster, he put a Sting Ray on it and it took care of a lot of the problem. What is the motor on?
Rodney

[WTodd]

The cheapest way to do it is buy a "whaletail", they are easy to install and work great, they also help your holeshot. I've used the Sting Ray Classic with very good results, a friend had a Hydro Sport with a 150 on it, chine walk monster, he put a Sting Ray on it and it took care of a lot of the problem. What is the motor on?
Rodney

Lowe ST175.....I'll look into the "whaletail"


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[Oldfart9999]

The make I'm familiar with is the Sting Ray, the classic model, the boats I used them on they helped my hole shot and the boats didn't "blow out" as much on hard turns.
Rodney 

[WTodd]

The only issue I'm experiencing is losing "grip" on the way up to plane in what I call dirty water; following someone else that just got on plane so the whale tail may be the better solution


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[Oldfart9999]

Let us know what you get and how it works out for you.
Rodney

[WTodd]

I ended up getting the Stingray StarFire because no drilling but we'll all have to wait a month since this is 1 of my Christmas presents. After I install it and use it I'll provide a pic and tell you how it performed.


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[FloridaFishinFool]

The only issue I'm experiencing is losing "grip" on the way up to plane...

Your problem may be ventilation. Here is an article on it:

Is it cavitation or ventilation?

http://www.louisianasportsman.com/details.php?id=1795

"Ventilation is the result of air or exhaust gases being pulled into the propeller blades. This causes the blades to lose their grip on the water, the engine RPMs go up and the forward speed of the boat is reduced."

[WTodd]

Your problem may be ventilation. Here is an article on it:

Is it cavitation or ventilation?

http://www.louisianasportsman.com/details.php?id=1795

"Ventilation is the result of air or exhaust gases being pulled into the propeller blades. This causes the blades to lose their grip on the water, the engine RPMs go up and the forward speed of the boat is reduced."

I read a little about it the other day; the "whale tail" should eliminate the issue.


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[FloridaFishinFool]

I read a little about it the other day; the "whale tail" should eliminate the issue.

I use one too- a smaller one, but mainly for stability and getting up on plane a lot faster. I do like the added stability it provides me at WOT.

It may solve your problem. I say may solve it because if you are having an issue related to the physics of your setup, simply adding the fins may not address why your prop is drawing in air or exhaust bubbles at its particular location at certain speeds. Sometimes this type of problem has something to do with hull shape and how water flows over and past the hull at different speeds and what sort of spinning vortexes are created just behind the hull where the prop is.

So I hope you are right and that adding the fins do solve your problem. If it does then great. If not, then a deeper look into why your prop is losing "grip" might be in order.

I have had friends in the past with similar problems. One solved it with a jack plate that moved the prop back away from the transom far enough to solve his problem- and I think he was then able to run it a little deeper too- while another friend tried everything the "experts" told him to do until he finally solved his problem by selling the boat and getting another one.

Good hull designs go a long way to helping to prevent this problem. Hull designs that tend to divert water flow displacement vortexes away from the prop so the prop can turn within solid water not spinning vortexes with exhaust and air bubbles drawn in.

My fishing buddy who sold his old bass boat had one of the problems mentioned below from the article and if I recall correctly his was a 'rocker':

"Ventilation can also come from exhaust gases being introduced into the blades of the prop. Most propellers have some sort of ring around the trailing edge of the exhaust hub. This ring creates a high-pressure barrier that prevents exhaust gases from being sucked back into the blades.

Other sources for ventilation include the leading edge and sides of the motor's lower unit and the bottom of the boat. Inspect your lower-unit housing for any imperfections in the surface directly in front of the propeller. Knicks, gouges, scratches or barnacles can all disturb the water flow to the propeller, and cause ventilation.

The same is true for the bottom of the boat. Holes and chips in the bottom surface from such things as oyster reefs can cause disturbed water flow to the propeller. Depth-finder transducers and live well or wash-down water pick-ups or drains could disturb the water flow to your propeller.

In the case of a boat that has a little age such as the one mentioned in the e-mail, you should check the condition of the bottom. The boat bottom should be perfectly straight for at least 5 feet forward of the transom.

The boat can be checked with a long straight edge placed along the bottom from transom forward. If the bottom is concaved upward from the straight edge, you have a condition called a hook. If the bottom is convex, the condition is called a rocker.

A hook in your bottom will cause the boat to have excessive transom lift. As your speed increases the pressure of the water flowing under the hook in your bottom will cause the transom of the boat to lift out of the water and the bow to be pushed down. Ventilation occurs because the propeller is being pulled closer to the surface.

A rocker will generally cause your boat to porpoise at running speed.

Ventilation or cavitation, they are both bad for your boat."

Good luck solving the problem and keep us informed!

[WTodd]

I use one too- a smaller one, but mainly for stability and getting up on plane a lot faster. I do like the added stability it provides me at WOT.

Any benefits other than never losing "grip" getting on plane will be an extra and much appreciated


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[Bud Kennedy]

I do see folks with "whale tails" but always wondered what the real problem is.  My question is what brings about the need to add this device.  Is it due to hull conditions, improper set up, prop selection or is it just because the boat has an under sized motor. 

A lot of the boats i see then on typically are smaller aluminum boats with 60hp or less motors.  Also not that uncommon to see them on some of the fiberglass skiffs being used in the salt water creeks.

[FloridaFishinFool]

I do see folks with "whale tails" but always wondered what the real problem is.  My question is what brings about the need to add this device. 

Most outboard motors already have similar fins on the lower unit. Adding the additional fins is merely extending what is already there. The added fins are an extension of the cavitation plate.

Take a look at these modern high powered bass boat at WOT.





Steering control at speeds like this are a must. The boats above are doing more "flying" than it is in the water. It would be very easy to lose control over a boat moving at this speed. Is he boating or flying at this speed? The man is out of the water in the above image. How much faster can he go before the air picks up the bow and flips the boat? How about a strong side wind? What if he hits a wave and ramps out of the water? What control will he have? None at that point.

Boats like the above are right on the edge of losing it which could kill the occupants and others around them.

Adding some small fins on the lower unit does provide increased stability and helps lock the boat into the water better.

Sometimes the problem is just the desire to have the biggest motors, most horsepower, and fastest ride between fishing spots. Adding the fins makes it a tad bit safer between fishing spots is all. And then some complain the added fins slows them down 1 or 2 MPH. But they are a little safer and more in control even if a little slower.

I don't really notice the boat being slower in my case. I know I overpowered my old boat. So I added the fins to give me more control and especially more stability when using every horse bolted onto the transom.

[loomisguy]

First call Lowe and see what prop they recommend, A 22 sounds about right.
It sounds like either the motor is up a hole too high or you may just be over trimming it.

[fishandkamp]

I sent you an email about my Lowe Stinger 170.

[WTodd]

Got it fish. I installed a whale tail (StarFire) and it appears to have fixed my issue....small sample size but I definitely noticed a difference getting on plane faster


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[Oldfart9999]

Good deal!!
Rodney