Finster
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trim fin
So, if you have read my other posts, you know that I just put a evinrude 90 HP on my 16 foot alum deep v. I upgraded from a 40 HP. Wow! it is impressive like an entirely different boat! This motor came with a trim fin on it. I don't even use my power trim anymore. I just lower the motor and hit the gas. The boat planes itself perfectly. In fact, when I try and use the trim I just porpose. My question is, could I get more speed or better gas mileage if I took the fin off and used the power trim?
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nwpaconcours
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You will get some responses that they are terrific. You'll get some responses that they just add drag. Personally I've always figured that if they improved performance for all boats then the motor manufacturer would have them on to start with. After all, if they can make their motors perform better with a pretty simple change like that, why haven't they done it already? But plenty of folks swear by them. Maybe get some time with it on...then take it off and see how your performance changes?
post edited by nwpaconcours - 2010/05/21 10:16:15
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nwpaconcours
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So you got your stalling problem fixed? Why not post the fix in the threads you started to help others who might have had problems, or to at least close the discussion. Just always helpful for others to end a "I have a problem please help" discussion.
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Porktown
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I can't imagine wanting much more speed than a 90hp is giving your 16ft. aluminum boat... My 50 has them as well, they do seem to get you on plane quicker on then off. Top speed may be a bit better off, as well as steering response, but nothing noticable IMO (much slower motor though). If you are shooting from one spot to the other, I'd take on plane faster, over better top end. If you are using it to get out to the walleye/perch waters or long distant cruising, then that extra mph or two could come in handy.
Congrats on the new motor, sounds like fun!
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Blowchowski
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Take it off and try it without it. It may be masking other problems like having the motor mounted too low on the transom.
I love cats. I just can't eat a whole one..
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gizmos
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Had fins on two boats and the plane was much quicker. Didn't notice much on the top end. One was a 65 the other an 85. Dont have one on the current ride. No need and I like the ability to tweek the trim in top end as conditions permit. M.O. 
Eat what you catch,troll for cows.
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Finster
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So you got your stalling problem fixed? Why not post the fix in the threads you started to help others who might have had problems, or to at least close the discussion. Just always helpful for others to end a "I have a problem please help" discussion.Â
No, stalling is not fixed. I will post the answer if and when I figure it out.
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anzomcik
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When you fix it
The best way to see is by trying with and with out.If you got it on now, go out and make a chart and write down your speed at 1000rpm, 1500rpm....WOT then try with out it. Make sure you got a accurate tach and gps those are super important. Make sure the motor falls in the upper portion of the WOT range of the motor.
Also the biggest improvment would be a prop, and you will need to know what i wrote above, and with out a tach or gps you will be guessin. I have set up an outboard to make them run there best more than once. The more info that accurate the better.
To me all out top speed is not worth a poor handling boat, and on the lake it is rare to run wide open even a 1foot chop will take the wind out of your sail go for nice plane speed and you will be a happy camper
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DarDys
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Back when I was in the boat biz, I asked an aquaintance of mine, who happened to be the VP of large outdoor development for Mercur,y if adding a fin was beneficial. He just laughed and said, "Sure it is. They pay me over $200K (in 1996) to hydrodynamically design lower units for outboards, but you can improve on that by bolting a $50 piece of plastic designed to fit any brand of motor to it."
His point was, if the boat was set up correctly int he first place -- right mounting height, right prop, not over or under powered for the boar AND load -- there was no need for a fin.
The poster formally known as Duncsdad Everything I say can be fully substantiated by my own opinion.
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bulldog1
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"Sure it is. They pay me over $200K (in 1996) to hydrodynamically design lower units for outboards, but you can improve on that by bolting a $50 piece of plastic designed to fit any brand of motor to it." They way most places are doing business these days, I'm surprised they didn't just fire him and start bolting them on... 
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DarDys
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"Sure it is. They pay me over $200K (in 1996) to hydrodynamically design lower units for outboards, but you can improve on that by bolting a $50 piece of plastic designed to fit any brand of motor to it."
They way most places are doing business these days, I'm surprised they didn't just fire him and start bolting them on...
Bull, Notice the date -- 1996. Things were different back then. He was obviously being very sarcastic about the fins. This guy was good. He came up with the V-6 gearcase for bass boats that bridged the gap between the normal V-6 gearcase which was more power laden, but lacked speed ability and the X2, which didn't have enough "stuff," but was fast once on plane. He also developed fuel injection and oil injection in Mercury outboards. He once took me into Mercury's Lake X facility and got me though the area where they do gearcase testing and development. It was pretty cool.
The poster formally known as Duncsdad Everything I say can be fully substantiated by my own opinion.
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BloodyHand
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I put 1 them fins on a 50 hp merc, that was on a 14.5 ft. boat. It worked wonders for me. It planed the boat out in a hurry. I think the prop pitch was too big and that's why it took forever to plane.
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Meatball
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I have a cobra plate on my 16' with a 40 hp. No drop in top end but definately helps keep the bow down on take off and powering up rivers at part throttle. I noticed a drop in top end speed withe othe hydrofoils on smaller boats, notibly doelfin. Jesus, 90 hp? On a tuna can? wow, that thing should fly.
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Finster
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I have a cobra plate on my 16' with a 40 hp. No drop in top end but definately helps keep the bow down on take off and powering up rivers at part throttle. I noticed a drop in top end speed withe othe hydrofoils on smaller boats, notibly doelfin. Jesus, 90 hp? On a tuna can? wow, that thing should fly.
LOL... yea, I just put this on last fall and only ha a chance to run it once. I had 3 people, a full load of gear and a cooler full of what not.... Still go up on plane in about 15 seconds and did almost 40 mph.... If it was not for the stalling issue, life would be perfect.
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anzomcik
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15secounds to plane, that seems a little long for such a lrage motor. My 14 foot heavyly weighted aluminum gets on plane well under 10secound. with a 25hp
My crestliner 3000lbs just the boat add 800 peple+ 200 lbs gear with 4.3 will jump on plane 5 seounds.
I have a buddy with almost the same motor as yours, its on plane like right now on a 17 foot fiberglass boat.
I think you might need a setup adjustment, things to me are not adding up just my opinion
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Finster
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15secounds to plane, that seems a little long for such a lrage motor. My 14 foot heavyly weighted aluminum gets on plane well under 10secound. with a 25hp
My crestliner 3000lbs just the boat add 800 peple+ 200 lbs gear with 4.3 will jump on plane 5 seounds.
I have a buddy with almost the same motor as yours, its on plane like right now on a 17 foot fiberglass boat.
I think you might need a setup adjustment, things to me are not adding up just my opinion
Take int considertion that I had roughly 700 lbs worth of people and gear in the boat at the time. 15 seconds is just a rough guess since I was not timing it.
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DarDys
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15secounds to plane, that seems a little long for such a lrage motor. My 14 foot heavyly weighted aluminum gets on plane well under 10secound. with a 25hp
My crestliner 3000lbs just the boat add 800 peple+ 200 lbs gear with 4.3 will jump on plane 5 seounds.
I have a buddy with almost the same motor as yours, its on plane like right now on a 17 foot fiberglass boat.
I think you might need a setup adjustment, things to me are not adding up just my opinion
Take int considertion that I had roughly 700 lbs worth of people and gear in the boat at the time. 15 seconds is just a rough guess since I was not timing it.
Just a question -- Is 700 lbs within the BIA rating for a 16 foot boat?
The poster formally known as Duncsdad Everything I say can be fully substantiated by my own opinion.
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anzomcik
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Ok so you were shooting from the hip, then i can understand just guess, but if it happened in real life you have set up issues
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Finster
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Just a question -- Is 700 lbs within the BIA rating for a 16 foot boat?
I can't remember what the rating is without going out to look, I'm thinking 1200 lbs max. I know it's rated for seven people. However, with seven people, we would have to sit on each others shoulders.
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DarDys
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Just a question -- Is 700 lbs within the BIA rating for a 16 foot boat?
I can't remember what the rating is without going out to look, I'm thinking 1200 lbs max. I know it's rated for seven people. However, with seven people, we would have to sit on each others shoulders.
Do take a look. The 1200 lbs is probably listed as "people, motor, and gear" and there will be another really much lower rating for "people and gear." Just trying to save you an incident with your insurance should you have an accident -- yes, I have seen claims denied because the boat was overloaded based on the BIA rating, even if that was not the cause of the accident.
The poster formally known as Duncsdad Everything I say can be fully substantiated by my own opinion.
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Finster
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Do take a look. The 1200 lbs is probably listed as "people, motor, and gear" and there will be another really much lower rating for "people and gear." Just trying to save you an incident with your insurance should you have an accident -- yes, I have seen claims denied because the boat was overloaded based on the BIA rating, even if that was not the cause of the accident.
I took a look: 900 LBS or 7 people 1600 LBS people, gear, motor 90 Hp max
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REEL FORCE
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Are we talking about the trim fin above and behind the prop ? if so this is to help with your steering ...got a pic ? too many trim fins to really telling what the exact kind your talking about ...
post edited by REEL FORCE - 2010/06/11 00:03:09
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