Minimum Planing Speed
 

Does propeller pitch affect minimum planing speed?

Re: Minimum Planing Speed
 

YES! Just back in from the first coat of Epifanes, but that`s another thread. I`ll start another one as that black magic is a hot topic.
GFS

Re: Minimum Planing Speed
 

It's not the forward momentum that lifts the hull to the planing position? My thinking is that a lower pitch prop would get there faster but at the same mph as a higher pitch. I have a 17 and 19 but they are different props. the 17 is a bow lifter and no good on the boat. the 19 picks the stern up and will plane at 15 - 17 mph. If I wanted a lower planing speed a 17 with same characteristics as the 19 might do it then?

Re: Minimum Planing Speed
 

A four blade will allow a lower planing speed.

Re: Minimum Planing Speed
 

Fr. Frank will probably chime in here with a technically correct answer, but I believe rake of the prop has a lot to do with it. Before I repowered, my Seafari would plane nicely at 12-13 mph with an ancient (but light!) 115 Evinrude running a 13 3/4 x 15 SST prop. Of course it's better balanced than a CC because helm is further foward and weight of the cuddy up front. When I repowered with a much heavier motor and a bracket w/30" offset, it would not plane below about 3500 rpm/25 mph with a 14.25x17 3B SS prop; a 14.5x19" 3B SS prop was a little better at ~2600/17 mph. This was a huge issue for me because I often like to be able to cruise at min planning speed offshore when the seas kick up.

Currently running 2 different Michigan 4B props, both of which plane easily @ 12-13 mph: 14x18 Vortex (Al) for heavy load planes at about 2700, and a 14.125 x 20 Apollo for light loads and a little better mpg, planes at about 2000. You have to be careful with the 4B props; some bass boat designs are BOW lifting! If description says designed for heavy offshore boats, it's probably STERN lifting.

Re: Minimum Planing Speed
 

RED,
I had a similar problem. To maintain a lower planing speed, I put one of those 'dolfins' on my outdrive. you have to be careful around the dock as if you contact something with it, you have more surface area working smaller cross section of the cavitation plate. The cavitation can be damaged. You will loose a knot of so on your top end, but when it gets sloppy, you can trip the drive down, slow your speed stick the bow right in it and it is much more comfortable. It was really needed with the old power. we will have to see how things go with the new power. just my experience.

Re: Minimum Planing Speed
 

Forgot to mention, I also have a Doelfin installed, on old motor as well as new one. For the low planning speeds, you generally have to trim motor all the way down and put the trim tabs down. On the 25" shaft new motor/bracket setup, engine trim seems to have much more effect on running angle than on the old 20" shaft motor hung on transom. Maybe there's some extra leverage involved with the 30" setback on the bracket!

Re: Minimum Planing Speed
 

No fin but do have tabs which knock off about 5 mph. Not really concerned about top end but with fuel prices I've been takeing two passengers to help with the cost. I' d like to be able to plane easier and at a lower speed when it gets a little rough. The 19 is a michigan apollo and the 17 is a omc viper.

Re: Minimum Planing Speed
 

You might want to try a fin. They aren't that expensive and it should help. Also if you're going to Long Point, you could try one of my 4B props. If you have a 150, that 4B Apollo might work pretty well.

Re: Minimum Planing Speed
 

One of those fins does require drilling 4 holes in the cavitation plate. I was a little skeptical at first, but a friend of mine put one on his 23, and I was extremely impressed with the difference it made. That is what convinced me to put on on my boat. If you are trying to obtain a lower planing speed for comfort in a sea condition as well as to conserve on fuel, it is the right modification. I think mine was like $40 at west marine or something like that. It was teh least expensive, 1-piece fin I could find, and over the course of 1 season (in the northeast, short season) it more than paid for itself.

Re: Minimum Planing Speed
 

I want a lower planing speed for all of those reasons PLUS its almost time to start crusin the beaches in search of the silver king.

Re: Minimum Planing Speed
 

Do es the fin in any way make the stern dig down during a hole shot. I fish the flats often and only have a couple of pot holes that are barely deep enough for me to get up on plane.

Re: Minimum Planing Speed
 

and bikini clad ladies I might add :eek: :cool:

Re: Minimum Planing Speed
 

i had the fin on my old 150 evinrude on my 20. i took it off one day and could notice a big differenc in the way it would plane and the attitude of the ride. now ive got trim tabs and a merc 200 so i dont use it now. if you dont have tabs id get one.

Re: Minimum Planing Speed
 

The fin works like an airfoil, so it depends how you use it. If you trim the motor down so the airfoil has a positive angle of attack, you'll get stern lift which is why it helps you plane at lower speeds. If propshaft is parallel to surface, you won't get any lift, just a little drag which will knock a couple of mph off your top end. If you trim motor out/up, the foil will have a negative angle of attack and stern will probably dig in.

Re: Minimum Planing Speed
 

Thanks for all the comments. I believe I'm going to try the SE Sport model 300. A little research shows that this model is not the wing design which does have some negatives such as diging during a sharp turn. The narrower design of the SE Sport brand doesnt have the flex of the wing design.

Re: Minimum Planing Speed
 

i think thats the one i had on my 150. i didnt know much about trim of the boat, but i lost 2 mph without the fin. i went from 38 down to 36 no matter how much i played with the motor.

Re: Minimum Planing Speed
 

So maybe I could see top end increase like some of the reviews said. That would be great.

Re: Minimum Planing Speed
 

At high speed the fin should be out of the water so I should be able to use trim the same way I do now. Am I thinking right or will I lose my high speed trim-up ability?

Re: Minimum Planing Speed
 

The fin attaches to cavitation plate, so I doubt it'll ever be clear of the water, unless you have motor set really high or on a jack plate! It will not effect your ability to trim the motor out; it may help reduce porpoising, or may allow you to trim out more before that happens. As for different styles of fins, I've seen some, maybe like the one you mentioned, that are relatively narrow but extend further aft, and may generate some lift by capturing/deflecting some of the prop wash. In general a high aspect ratio airfoil (like on a sailplane) is most efficient, i.e., it produces the least drag for a given amount of lift; delta wings, like the Doelfin, are also pretty efficient. I'm not an expert in hydrodynamics, but I believe there are a lot of similarities to low speed aerodynamics, where the flow can be considered incompressible for all practical purposes.

I'd be surprised if a fin actually increased top speed, unless the boat was badly balanced (very stern heavy) to begin with!

Re: Minimum Planing Speed
 

You guys might want to read through this post form last summer.

Fr. Frank chimed in with some real good insight and information. (so, what else is new...the guy has lived most of this stuff!)

http://www.classicseacraft.com/forum...rev=#Post53203

Re: Minimum Planing Speed
 

I have used the doelfin and currently we just put a stingray fin ($48)from West Marine on the new Zuke 140 on an 18SF. The planning speed dropped nicely and the fin does lift the stern up on take-off. There is no noticeable digging-in at turns and the extra side to side wing length vs. a more narrow one should only improve it's function. The narrow plates work great just different.

Re: Minimum Planing Speed
 

Hows the saying go? Surround yourself with intelligent and successful people, listen to them, do as they do, and you'll turn out the same. I'll get a stingray this weekend. Thanks for the input.

Re: Minimum Planing Speed
 

That priced model looks to be the drill holes to mount model. No concernes about doing that to an under warrenty motor. Mines an old 150 so I don't care. What that Suzuki weigh? I think my Johnsons about 375. Were probably close in performance except for 1 big factor; fuel economy. I get about 2mpg max.