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Author Topic:   Hydrofoil on an Outboard
Florida15 posted 02-14-2003 10:24 AM ET (US)   Profile for Florida15   Send Email to Florida15  
Does anybody have experience with a Stingray hydrofoil stabilizer on their outboard ? I have a 15'with a 50 Johnson on it and it seems slow to get up on plane. I hate the way they look out of water but have heard they help get the boat on plane quicker.
kingfish posted 02-14-2003 11:45 AM ET (US)     Profile for kingfish  Send Email to kingfish     
Don't have experience with a Stingray, but I do with a DoelFin, on two Montauks, a 24' IO and an OR22, and they worked great - got the boats on plane sooner and allowed them to stay on plane slower. Stingray may very well work just as well as DoelFin; just haven't tried them.


Baseline posted 02-14-2003 02:22 PM ET (US)     Profile for Baseline  Send Email to Baseline     
I have used both DoelFin and Stingray hydrofoils my outboards. I have used the DoelFin on a 11 foot Zodiac with 20hp outboard, and a 20 foot Rinken with 120HP OMC Stern drive. The DoelFin help both boats, plan noticeably faster and stay on plane at lower speed.

The Stingray hydrofoil came on my Montauk with a 90 hp Johnson, so I do not know how it runs without it. However, the Montauk with the Stingray planes much faster, than the Rinken with the DoelFin; the whaler has a much better HP/Wt ratio. The Montauk is up on plan almost instantly. The Montauk stays on plan pretty well at low speeds.

where2 posted 02-14-2003 06:28 PM ET (US)     Profile for where2  Send Email to where2     
What's your tach read at Wide Open Throttle? If it's below 5K rpm, then you're propped wrong and would be better off lowering your prop pitch. I suspect you've got a 13x17" right now, which would maximize WOT speed, but hurt hole shot. If you've got a 13x15" on there, then the boat should jump out of the water, but have a low 30-35mph top end at WOT. With a 17" pitch, you might be getting 34-38mph.

Check your WOT RPM before you go out to buy the fin.

Another thing to try is shifting the weight layout in the boat. If you're carrying passengers, plant one on the anchor locker at the bow, and compare your time to get on plane to that with the passenger on the rear seat. If carrying 3 people in the boat, plant one on the front thwart, and one on the anchor locker. Then try again, with the guy from the bow sitting next to you at the helm. It makes a difference where the weight is, especially if you're slightly over-propped and running average Hp.

Even with maxed out Hp on my 15', I can tell differences if I have a slalom skier behind the boat, slightly overpropped engine, and move my passenger around inside the boat.

Florida15 posted 02-14-2003 07:18 PM ET (US)     Profile for Florida15  Send Email to Florida15     
I bought the boat used and it does not have a tach.
When someone is riding up front, it gets up on plane quickly but it has side by side pedastal seats and I do not want to make someone ride up front when there is an empty pedastal seat.
I wish there was someway to put the gas tank up front. If I could put some weight up front, it would definetly solve the problem. I figured a hydrofoil would be the easy answer.
Clark Roberts posted 02-15-2003 08:39 AM ET (US)     Profile for Clark Roberts  Send Email to Clark Roberts     
The Doel-Fin is a hydrofoil and creates lift via "air foil" shape (straight bottom surface and curved upper surface) while the Stingray is a hydro-spoiler (turned down trailing edge). The spoiler will benefit stern heavy inboards by helping raise stern but can kill top speed and high speed handling/economy on lighter outboard hulls. Happpy Whalin'... clark
weekendwarrior posted 02-15-2003 09:29 AM ET (US)     Profile for weekendwarrior  Send Email to weekendwarrior     
Lots of people seem to be pleased with these things. A friends father has one on their boat and they say it made a big difference, but the ventelation plate on the motor that it's bolted to broke off after some period of use. They had it welded back on and keep using it (don't remember what brand?) because it makes such a difference. Anyway I was curious if anyone else has had broken ventelation plates while using one of these things?
Florida15 posted 02-15-2003 11:03 AM ET (US)     Profile for Florida15  Send Email to Florida15     
Clark, that's strange that you've had that experience. Stingray actually advertises that it will not only get your boat up on plane in half the time but will also increase top speed and fuel economy.Maybe it
depends on the boat/motor combination? They also actually have hydrofoil in the name. The post concerning the cavitation plate breaking off does concern me though. I wonder how common that is ?
kingfish posted 02-15-2003 11:47 AM ET (US)     Profile for kingfish  Send Email to kingfish     
I think it is helpful to visualize what one of these things is doing at high planing speeds. If a motor is set up for optimum performance, the cavitation plate is *above* the level of the water as that water flows under the transom at high planing speeds.

So, unless there is a downward-angled spoiler, as Clark has described the Stingray to have, no part of the fin is even touching the water at WOT, so it *can't* affect top end, one way or the other. That trailing fin on the Stingray, if it had any effect at all at top end, would act to raise the stern, thus lowering the bow and increasing wetted surface which would in turn lower top end.

These things really aren't going to do anything to top end speed unless the motor is improperly set up and/or the fin has a spoiler like the Stingray, and then all they'll do is lower top end and potentially make the boat squirrelly at WOT. Their advantage lies at lower planing speeds, and in getting the boat on plane more easily.


bc posted 02-15-2003 12:00 PM ET (US)     Profile for bc    
I've used both on the same setup. (Note: I personally don't like the looks of any of the foils) The boat was a 16' Sundance Skiff with a over-rated 40 evinrude tiller setup. Boat came with the motor and max rated 25 tiller/30 remote. Anyway, the boat porposed badly (uncontrollable) at any of the trim settings. I first installed the stingray which corrected the problem. Pushed the bow down nicely. I didn't like the size and look of the stingray so I purchased the doelfin. With the doelfin, the effect wasn't as drastic. The skiff porposed a little at 3/4 throtle and somewhat more at full. The skiff would run in the mid to upper 30's with the 40HP. I later sold the 40 evin and replaced it with a tiller 25 merc. Dropped the speed to around 30 but no porposing and didn't have to use the fin. I liked this setup the best. I think the stingray is out in the garage. If someone wants it the price is free99 + shipping.
Bigshot posted 02-15-2003 12:44 PM ET (US)     Profile for Bigshot  Send Email to Bigshot     
I had a 15 with a 48hp and a 17" prop and she would holeshot great. How heavy are you and your passenger? If engine is trimmed down/in she should plane real quick, then trim it up. I have never thought doelfins are necessary on 15-17 Whalers unless you like to plane at 12mph.
gss036 posted 02-15-2003 03:04 PM ET (US)     Profile for gss036  Send Email to gss036     
I have run a Stingray on my Merc200 for thepast 12-13 years. I have several dings in it from junk coming under the boat. We seem to have a lot of that here in Puget sound w/all the rivers duming into the bays. We also have a lot of wind and short chop on the water that keeps you from getting up and running at a decent speed so the Stingray works wonders for me when I have to run at 15 kts in windy chop. I agree that when you are up and running it probably is out of the water as I trim my motor up as it gets more RPM and helps on the fuel consumption. I try to run around 4200-4400 RPM w/ mt Seacraft 23WA and that gets me around 28-29 kts most of the time and my last fill up after 5.5 running at this speed was 50 gallons of reg gas. Just my 2 cents Gary
Florida15 posted 02-17-2003 10:29 AM ET (US)     Profile for Florida15  Send Email to Florida15     
bc, I would love to try the Stingray.
I'll be glad to pay for shipping. E-mail me please. Thanks.
bc posted 02-17-2003 07:04 PM ET (US)     Profile for bc    
email sent
lpaton posted 02-18-2003 07:12 AM ET (US)     Profile for lpaton  Send Email to lpaton     
Had a Doel Fin on my Outrage III. Great to get up on plane and stay there at lower speeds but stopped using it when ventilation plate broke off after running over a fairly small semi-submerged branch
witsendfl posted 02-18-2003 01:05 PM ET (US)     Profile for witsendfl  Send Email to witsendfl     
I have used both the STINGRAY and the DOELFIN. It is amazing how much those items have gone up in price! I bought my 1st one back in 1986/87 for a I/O. The product worked great. I also had one on a 1983 70 HP Johnson, rigged on a 83 15 sport.

The product allows faster planning, flatter turning. What I mean by that is the boat will not lean as much in a turn. It prevents alot of bow rise when there is alot of weight placed in the back. (Tanks batteries, people etc). If you are to pull anykind of skiing activity it is a large help.
Part of the design on the Hydrofoil is so you do not need to move a bunch of stuff around

Make sure that you etch your 4 screw holes as far back on the cavitation/ventilation plate as possible. The farther back the better.

Good Luck and hope these comments help...

witsendfl JimK

jimfar posted 02-18-2003 04:26 PM ET (US)     Profile for jimfar  Send Email to jimfar     
I had a DoelFin on my Montauk. When I added a CMC jack-plate I removed the Doelfin in favor of a Nedski Foil. The ability to stay on plane at only 12-15 MPH is invaluable in rough water. With the Nedski Foil when I give it a little throttle it pops right up on plane. My boat's a lot quieter too. Steering is also enhanced. I no longer fight the steering wheel at high speed. I highly recommend the set-up I've put on my Whaler. I run the Galveston bay system. The conditions vary drastically from 1 foot or less to deep swales in the open bay. Itís really ugly, but my jack-plate / Nedski setup is the best single investment Iíve made on my Montauk. Check out the Nedski Foil.
fester posted 02-19-2003 01:23 PM ET (US)     Profile for fester  Send Email to fester     
Have been considering a doel fin or other type of hydrofoil for my 20' Outrage. My hope is that this would help keep the boat on a plane at a lower speed. The typical scenario for me is that often times the due to the chop the comfortable speed is about 17 knots. Problem is boat does not always stay on a plane at this speed. I'll be going along and then hit rougher chop or a larger swell and then I'm off the plane.
How much do you think a hydrofoil will help? Which type do you guys like and do they all require you to drill holes in the caviation plate?
Thanks, Jeff
Bigshot posted 02-19-2003 01:50 PM ET (US)     Profile for Bigshot  Send Email to Bigshot     
Ok for all you that wish to try one or even run one do this....Install the doel fin or whatever brand you buy but only use the one set of bolts that are farthest aft. This is for 2 reasons: 1) if you do not like it you only have 1 set of holes(that you really do not need to fill). 2) If you do like it and hit something you have a better chance of it ripping out than breaking your anticavitation plate. Plus it will not perform any different than with both sets drilled. If you hit your local marina, I bet someone will give you a set for free. My bud who is a mechanic has sets of these lying around and he just gives them away to "customers" who want them. A place that sells rebuilt engines probably has mucho sets.
jameso posted 02-20-2003 09:26 AM ET (US)     Profile for jameso  Send Email to jameso     
Florida guy.
I have two 15's both have 50's and believe me the hole shot is great on both. My 83 wi th 83 50 HP,OMC twin will throw you over the transom on take off. NO DOEL OR STINGRAY NEEDED. Raise engine 2 inches off transom and experiment with trim. Also you may have too much weight in back of boat.
The fins will get you on plane sooner but you should not need them, I am of the school that says the less drag in the water the better.
I just gave away both a Doel and a Stingray, sorry.
Jim Armstrong
Florida15 posted 02-20-2003 10:39 AM ET (US)     Profile for Florida15  Send Email to Florida15     
Jim, I am sure that too much weight in the back of the boat is the problem. That's why I plan to go to 2 6 gallon tanks instead of one 12. I wish the console was a little further forward. I plane quickly when somebody is sitting up front but when it's just me (220 lbs) and a buddy (190 lbs) it takes a while to get up on plane. I will experiment with the trim though. Thanks.
jameso posted 02-20-2003 02:34 PM ET (US)     Profile for jameso  Send Email to jameso     
Don't want to sound wise a** but two 6 gals equal 12? Also gasoline only weighs about 7 lbs per gallon, not much weight reduction.
As far as the weight of the captain, can't help you there but I also weigh 15 stones or so and my oft parner is no lightweight.
You may want to weigh the boat,motor ect. See other threads for that.
What is speed at WOT? My 50 does 37/38 with myself 8 or so gallons of fuel,battery and assorted beverages.
email me if you have any specific questions.

Florida15 posted 02-21-2003 12:30 PM ET (US)     Profile for Florida15  Send Email to Florida15     
Jim, you are right. Two 6s equal one 12 but I was going to put the reserve tank up in front of the console.
My motor has an aftermarket CMC tilt on it.
It seems to create quite a wash around the motor at low speeds. Think that could have anything to do with it ?
I don't know the top speed as I do not have a speedo on the boat. It is pretty fast though after it gets up on plane so I'm sure it's not waterlogged if that's what you were thinking.
jgdaniel posted 02-27-2003 03:57 PM ET (US)     Profile for jgdaniel  Send Email to jgdaniel     
I have 1972 17 standard with a 1979 Johnson 70,13x17 prop and elec tilt. Seat and console have been moved sternward,2 batteries under console and 19 gal Tempo under seat. Was slooow to plane and then porpoised unless the bow was down close to the point of "pushing" water. Weight up front always helped. Top speed,alone,per my Hummingbird paddle wheel was 30 mph. No idea what my true speed was. Installed the Doelfin, comes on plane much better but bodies up front are still best,no porpoising,steering feedback is lessened,doesn't fall off plane as quickly and the paddle wheel says I lost 1 mph.
Bigshot posted 02-27-2003 05:13 PM ET (US)     Profile for Bigshot  Send Email to Bigshot     
30mph with a 70 swinging a 17" prop, should be about 38mph.
credditt posted 02-27-2003 09:10 PM ET (US)     Profile for credditt  Send Email to credditt     
I used to have an 11' Sport with a Johnson 20 hp. I put a hydrofoil on it to help it plane quicker for pulling skiers. It seemed to help very slightly, and didn't slow the top end at all.

I then got a 1995 Dauntless 13. It's powered by a 50 hp 3 cylinder Evinrude and has a 15 gallon fuel tank under the rear deck (it has the fishing package). It is WAY too stern heavy, and it porposes and chinewalks badly when trimmed out. A hydrofoil helped ever so slightly with both issues, but it slowed the top end by a bit more than 5 mph. I plan to remove the hydrofoil and add some trim tabs. Tabs in the full up position are effectively turned "off", so they don't create any drag or decrease top speed, but can do a good bit to help chinewalking and porposing.

huladick posted 03-03-2003 04:52 PM ET (US)     Profile for huladick  Send Email to huladick     
Sounds like lots of pros and cons to these things. I, too, am thinking about adding one. I have a 13' w/35hp. With 2 people on the aft bench seat, it has a lot of trouble getting up on plane. How much of a problem is the anti-cav plate breaking with a plastic foil ? Thanks
Bigshot posted 03-03-2003 04:53 PM ET (US)     Profile for Bigshot  Send Email to Bigshot     
Plastic won't really hurt the plate, especially if you only use 1 bolt instead of 2 per side.
huladick posted 03-03-2003 06:57 PM ET (US)     Profile for huladick  Send Email to huladick     
Bigshot.... Will the plastic foil hold up OK with only one set of bolts ? Seems like it would tend to bend/crack. I've never run one of these, but I can see one in my future. Thanks, Dick M.
captbone posted 03-03-2003 07:37 PM ET (US)     Profile for captbone  Send Email to captbone     
Most of these problems can be corrected with proper weight distribution and proper trim. If you run a 13 whaler with two adults, 12 gallons of fuel and a cooler in the aft with a 25 hp then you are not running that boat properly. A doel fin will help in most areas but it will correct a improperly loaded boat. Sometimes you must stick someone in the bow, you can always have the come aft after your on a plane.
Bigshot posted 03-04-2003 09:50 AM ET (US)     Profile for Bigshot  Send Email to Bigshot     
My Checkmate did 55+ with one on it with just 1 bolt.

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