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Author Topic:   Doel Fin on 170 MONTAUK

Feejer posted 06-25-2008 05:15 PM ET (US)
I'm looking for any real world experince with a Doel Fin mounted on a Mercury 90 FOURSTROKE on a 170 MONTAUK. I've been doing a lot of tubing and skiing and find my speed somewhere between planing and not planing. Would [adding a DoelFin to a Mercury 90-HP FOURSTROKE on a 170 MONTAUK] help? What would it do if anything for steering and top end speed? I've searched for installation instructions but can't seem to find any. What needs to be drilled? There must be someone using it or something similar.
macfam posted 06-25-2008 10:05 PM ET (US)
Whether it was my 1964 Nauset, or 1987 13' Super Sport, or the 1982 Revenge V-20, ALL benefinted from a doel-fin or similar hydrofoil:
Lower planing speed
Eliminates/helps porpoising
More lift in the aft section, lowering bow
Accentuated trim, both up and down.
No appreciable loss in top speed(if engine is mounted at proper height)
Less "blow out" in hard cornering.
Most hydrofoils require 4 holes drilled in the anti-ventilation plate. Some brands are one piece, others (Doel-fin)are two pieces. There are some brands that do not require holes drilled, but I can't recall brand names.
I have always noticed a pronounced improvement.
Feejer posted 06-25-2008 10:46 PM ET (US)
I was looking at the no drill StingRay Jr XRIII Hydrofoil
sosmerc posted 06-25-2008 11:59 PM ET (US)
I have installed the standard doelfin in many applications and find that it is effective if the engine is installed at the proper height. One thing that I do...I move the back as far as possible before installing...this helps create more lift.
swist posted 06-26-2008 08:38 AM ET (US)
I am not necessarily pro or con these things, but I would point out that in more than one forum there are counter opinions that if an engine is set up properly (height, trim, prop, etc) then Doelfins don't really help. I tried one several boats back to solve some of the cited problems with little to show other than increased drag (few mph off top speed). Another point usually made is why aren't they on the engines to begin with if they solve all those problems.
Again, I am not taking sides here, but I suspect that the success of any given installation is probably a function of a lot of highly variable parameters which are different from boat-to-boat (and operator-to-operator).
Feejer posted 06-26-2008 09:15 AM ET (US)
Points well taken. The 1st thing before I install anything is to check is to see how far out of the water the engine cav plate is when I'm running WOT. Its my understanding that it should be an inch or two above the water.
gtxhal posted 06-26-2008 11:22 AM ET (US)
my first whaler was a guardian 17 divemaster (reinforced / modified montauk) with an evinrude 90. that boat almost always had six 80 cf tanks strapped in @ the stern, along with 3 divers / full gear. the doel fin made a huge difference in planing when we were loaded. (also helped for pulling 1 or 2 skiers up)
RLSmith posted 06-26-2008 01:12 PM ET (US)
I don't know if you do enough tubing and skiing to warrant the expense and complexity, but I use the trim tabs on my 2000 16' Dauntless when towing. This is particularly helpful when tubing kids, to very quickly get on plane at a reasonably low speed. Sometimes my younger kid's friends get scared when the speed climbs.
Feejer posted 06-26-2008 01:25 PM ET (US)
If had a Dautless 16 I would put tabs on it. The 170 does not really need them. I just like to drop my planing speed some.
fishinchips posted 06-26-2008 02:22 PM ET (US)
on my 170 it made a difference. It popped up the bow of the boat instantly. Lower planning speeds was acheived. However, lost of top end occured.
I did have to drill 4 holes on the cavatation plate.
You should email WT (warren), he had a fin that was mounted on the cavatation plate that requires NO HOLE drilling.
Ken
Feejer posted 06-26-2008 03:57 PM ET (US)
I was looking at the no drill StingRay Jr XRIII Hydrofoil
69wailer posted 06-27-2008 12:36 PM ET (US)
I have one on my 69 Nauset with a 2 stroke 90. Next to zero bow lift and the boat just goes. Definitely nice for tubing especially for those tight turns as I have found it difficult to pop the prop. Just hit the trim in a bit while powering through the turn as you apply the gas. We also use a bungi type of tow rope. Not sure if it hurts top end or mileage as the boat always had it on.
JayR posted 06-27-2008 05:37 PM ET (US)
I have not met anyone who was sorry they installed one...
Tom W Clark posted 06-27-2008 08:57 PM ET (US)
I sure have.
WT posted 06-27-2008 10:30 PM ET (US)
Here's a picture of my Turbo Lift.
http://smg.photobucket.com/albums/v665/warrent/Montauk%20Kicker/ ?action=view¤t=DSCN1293.jpg
No drilling required. Made of 100% stainless steel. I have found that it makes a big difference in large ocean swells. It seems to make my 170 Montauk track better.
Warren
JayR posted 06-28-2008 06:12 AM ET (US)
Tom, what were the complaints? Top speed?
That was the only drawback I had. I lost a few MPH. Well worth the sacrifice for the improved ride in nasty seas.
Feejer posted 06-28-2008 09:50 AM ET (US)
Do you have a web site for the Turbo Lift? I can't find anything on google.
maineidyl posted 06-28-2008 11:04 AM ET (US)
Could someone explain to me how mounting one of these would have any effect on top speed. It should be out of the water at top speed. There is so much controversy on these things.
Tom
WT posted 06-28-2008 11:53 AM ET (US)
Feejer:
Turbo Lift doesn't have a website. Search here for articles on Turbo Lift.
Here's one with the phone number for Turbo Lift. I ordered mine through the owner, Tom Happel.
http://continuouswave.com/ubb/Forum4/HTML/001898.html
Warren
swist posted 06-28-2008 11:54 AM ET (US)
It's not quite out of the water if it's mounted on the cavitation plate of the motor, which is normally an inch or so below the water. The effect on top speed seems to be pretty universally experienced if you read this thread and associated ones in other boating forums.
fishgutz posted 06-28-2008 04:41 PM ET (US)
Marine engines are designed with a large "anti-ventilation" plate, directly above the propeller. This plate is often mistakenly referred to as an anti-cavitation plate. Its purpose is to prevent air from being sucked into the propeller's blades from the surface.
http://www.cabelas.com/story-123/ross_prop_buyers_guide/212/ Performance%252BPropeller%252BBuyer%252527s%252BGuide.shtml
About half way down "Ventilation and Cavitation"
The anti-ventilation plate should be 1 inch ABOVE the surface of the water at top speed (or 1 inch above the bottom running surface of the boat), therefore a "doel-fin" type wing will having no affect on top speed. It would be mostly out of the water. Usually people have their motors mounted too low and then have a loss of top speed.
I have a Doel-fin on a 75 Merc 2 stroke on my Dauntless 14. Lower planing speed. Jumps on plane quicker.
Two huge advantages that few people realize. #1 I can accelerate to plane smoothly. I do not have to give it a lot of throttle. Keeps the ladies happy. #2 The ride in a chop is far less bouncy or jarring. Does a better job of keeping the boat at a constant speed in waves.
I'll bet these 2 advantages save me some fuel, too.
It is a rare instance that someone doesn't like a fin on their lower unit. And I'll bet if they didn't like it their motor isn't mounted correctly. I suppose there are a few cases where it just doesn't work. Generally heavy boats with heavy motors or motors with a little less horsepower. You wouldn't need one on a 170 if you ran a 115 or bigger motor.
Honda used to have a Doel-fin listed as an accessory for their motors on their website. If you look at a lot of performance reports you'll see some boats come with or were tested with fins attached by the boat or motor manufacturer.
fishgutz posted 06-28-2008 04:43 PM ET (US)
I used to have a link for the Turbo-lift. Then it just stopped working. They either went out of business or they just stopped making them.
lakeman posted 06-29-2008 06:25 AM ET (US)
If I were to put another fin doelfin fin type thing on my boat, I would put a Bob's Machine Shop type on. You can find them on the Web.
JayR posted 06-29-2008 02:41 PM ET (US)
Is there anyone here who would not use one again?
mikemdd posted 06-30-2008 11:17 AM ET (US)
I have a new Turbo Lift that I used once that I would like to sell. It fits my "newer model" (2007) Mercury 115HP FourStroke. Email me if interested.
Mike
sternorama posted 06-30-2008 03:53 PM ET (US)
Mikemdd-no email addy in your profile. email me...
sterno3000@gmail.com

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Author	Topic: Doel Fin on 170 MONTAUK
Feejer	posted 06-25-2008 05:15 PM ET (US) I'm looking for any real world experince with a Doel Fin mounted on a Mercury 90 FOURSTROKE on a 170 MONTAUK. I've been doing a lot of tubing and skiing and find my speed somewhere between planing and not planing. Would [adding a DoelFin to a Mercury 90-HP FOURSTROKE on a 170 MONTAUK] help? What would it do if anything for steering and top end speed? I've searched for installation instructions but can't seem to find any. What needs to be drilled? There must be someone using it or something similar.
macfam	posted 06-25-2008 10:05 PM ET (US) Whether it was my 1964 Nauset, or 1987 13' Super Sport, or the 1982 Revenge V-20, ALL benefinted from a doel-fin or similar hydrofoil: Lower planing speed Eliminates/helps porpoising More lift in the aft section, lowering bow Accentuated trim, both up and down. No appreciable loss in top speed(if engine is mounted at proper height) Less "blow out" in hard cornering. Most hydrofoils require 4 holes drilled in the anti-ventilation plate. Some brands are one piece, others (Doel-fin)are two pieces. There are some brands that do not require holes drilled, but I can't recall brand names. I have always noticed a pronounced improvement.
Feejer	posted 06-25-2008 10:46 PM ET (US) I was looking at the no drill StingRay Jr XRIII Hydrofoil
sosmerc	posted 06-25-2008 11:59 PM ET (US) I have installed the standard doelfin in many applications and find that it is effective if the engine is installed at the proper height. One thing that I do...I move the back as far as possible before installing...this helps create more lift.
swist	posted 06-26-2008 08:38 AM ET (US) I am not necessarily pro or con these things, but I would point out that in more than one forum there are counter opinions that if an engine is set up properly (height, trim, prop, etc) then Doelfins don't really help. I tried one several boats back to solve some of the cited problems with little to show other than increased drag (few mph off top speed). Another point usually made is why aren't they on the engines to begin with if they solve all those problems. Again, I am not taking sides here, but I suspect that the success of any given installation is probably a function of a lot of highly variable parameters which are different from boat-to-boat (and operator-to-operator).
Feejer	posted 06-26-2008 09:15 AM ET (US) Points well taken. The 1st thing before I install anything is to check is to see how far out of the water the engine cav plate is when I'm running WOT. Its my understanding that it should be an inch or two above the water.
gtxhal	posted 06-26-2008 11:22 AM ET (US) my first whaler was a guardian 17 divemaster (reinforced / modified montauk) with an evinrude 90. that boat almost always had six 80 cf tanks strapped in @ the stern, along with 3 divers / full gear. the doel fin made a huge difference in planing when we were loaded. (also helped for pulling 1 or 2 skiers up)
RLSmith	posted 06-26-2008 01:12 PM ET (US) I don't know if you do enough tubing and skiing to warrant the expense and complexity, but I use the trim tabs on my 2000 16' Dauntless when towing. This is particularly helpful when tubing kids, to very quickly get on plane at a reasonably low speed. Sometimes my younger kid's friends get scared when the speed climbs.
Feejer	posted 06-26-2008 01:25 PM ET (US) If had a Dautless 16 I would put tabs on it. The 170 does not really need them. I just like to drop my planing speed some.
fishinchips	posted 06-26-2008 02:22 PM ET (US) on my 170 it made a difference. It popped up the bow of the boat instantly. Lower planning speeds was acheived. However, lost of top end occured. I did have to drill 4 holes on the cavatation plate. You should email WT (warren), he had a fin that was mounted on the cavatation plate that requires NO HOLE drilling. Ken
Feejer	posted 06-26-2008 03:57 PM ET (US) I was looking at the no drill StingRay Jr XRIII Hydrofoil
69wailer	posted 06-27-2008 12:36 PM ET (US) I have one on my 69 Nauset with a 2 stroke 90. Next to zero bow lift and the boat just goes. Definitely nice for tubing especially for those tight turns as I have found it difficult to pop the prop. Just hit the trim in a bit while powering through the turn as you apply the gas. We also use a bungi type of tow rope. Not sure if it hurts top end or mileage as the boat always had it on.
JayR	posted 06-27-2008 05:37 PM ET (US) I have not met anyone who was sorry they installed one...
Tom W Clark	posted 06-27-2008 08:57 PM ET (US) I sure have.
WT	posted 06-27-2008 10:30 PM ET (US) Here's a picture of my Turbo Lift. http://smg.photobucket.com/albums/v665/warrent/Montauk%20Kicker/ ?action=view¤t=DSCN1293.jpg No drilling required. Made of 100% stainless steel. I have found that it makes a big difference in large ocean swells. It seems to make my 170 Montauk track better. Warren
JayR	posted 06-28-2008 06:12 AM ET (US) Tom, what were the complaints? Top speed? That was the only drawback I had. I lost a few MPH. Well worth the sacrifice for the improved ride in nasty seas.
Feejer	posted 06-28-2008 09:50 AM ET (US) Do you have a web site for the Turbo Lift? I can't find anything on google.
maineidyl	posted 06-28-2008 11:04 AM ET (US) Could someone explain to me how mounting one of these would have any effect on top speed. It should be out of the water at top speed. There is so much controversy on these things. Tom
WT	posted 06-28-2008 11:53 AM ET (US) Feejer: Turbo Lift doesn't have a website. Search here for articles on Turbo Lift. Here's one with the phone number for Turbo Lift. I ordered mine through the owner, Tom Happel. http://continuouswave.com/ubb/Forum4/HTML/001898.html Warren
swist	posted 06-28-2008 11:54 AM ET (US) It's not quite out of the water if it's mounted on the cavitation plate of the motor, which is normally an inch or so below the water. The effect on top speed seems to be pretty universally experienced if you read this thread and associated ones in other boating forums.
fishgutz	posted 06-28-2008 04:41 PM ET (US) Marine engines are designed with a large "anti-ventilation" plate, directly above the propeller. This plate is often mistakenly referred to as an anti-cavitation plate. Its purpose is to prevent air from being sucked into the propeller's blades from the surface. http://www.cabelas.com/story-123/ross_prop_buyers_guide/212/ Performance%252BPropeller%252BBuyer%252527s%252BGuide.shtml About half way down "Ventilation and Cavitation" The anti-ventilation plate should be 1 inch ABOVE the surface of the water at top speed (or 1 inch above the bottom running surface of the boat), therefore a "doel-fin" type wing will having no affect on top speed. It would be mostly out of the water. Usually people have their motors mounted too low and then have a loss of top speed. I have a Doel-fin on a 75 Merc 2 stroke on my Dauntless 14. Lower planing speed. Jumps on plane quicker. Two huge advantages that few people realize. #1 I can accelerate to plane smoothly. I do not have to give it a lot of throttle. Keeps the ladies happy. #2 The ride in a chop is far less bouncy or jarring. Does a better job of keeping the boat at a constant speed in waves. I'll bet these 2 advantages save me some fuel, too. It is a rare instance that someone doesn't like a fin on their lower unit. And I'll bet if they didn't like it their motor isn't mounted correctly. I suppose there are a few cases where it just doesn't work. Generally heavy boats with heavy motors or motors with a little less horsepower. You wouldn't need one on a 170 if you ran a 115 or bigger motor. Honda used to have a Doel-fin listed as an accessory for their motors on their website. If you look at a lot of performance reports you'll see some boats come with or were tested with fins attached by the boat or motor manufacturer.
fishgutz	posted 06-28-2008 04:43 PM ET (US) I used to have a link for the Turbo-lift. Then it just stopped working. They either went out of business or they just stopped making them.
lakeman	posted 06-29-2008 06:25 AM ET (US) If I were to put another fin doelfin fin type thing on my boat, I would put a Bob's Machine Shop type on. You can find them on the Web.
JayR	posted 06-29-2008 02:41 PM ET (US) Is there anyone here who would not use one again?
mikemdd	posted 06-30-2008 11:17 AM ET (US) I have a new Turbo Lift that I used once that I would like to sell. It fits my "newer model" (2007) Mercury 115HP FourStroke. Email me if interested. Mike
sternorama	posted 06-30-2008 03:53 PM ET (US) Mikemdd-no email addy in your profile. email me... sterno3000@gmail.com