Outboard motor fins

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Ted

Ted

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Jan 26, 2005
1,271
C&C 110 Bay Shore, Long Island, NY
Is anyone using outboard motor fins to help boost performance on an inflatable boat? (whale tail, doel fin, orca fin or others) I'm thinking of adding one of these to my 5hp and 8hp outboard motors which I use on an Achilles 9.5' inflatable boat. If there is an appreciable increase in performance, I won't need to use the 8hp anymore. I'm interested in actual user comments/experiences with motors under 10 hp. Thanks.
 
sailaway78

sailaway78

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May 11, 2005
3,431
Seidelman S37 Slidell, La.
I have never

I have never tried one of those on a dink, but have had a couple of them over the years, on small skiffs. Could never tell a bit of difference.
 
pogo2

pogo2

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Sep 26, 2008
97
Newport 30 Mklll North Tonawanda, NY
I have the doel fin on my 9.8 Nissan that is mounted on a 10' 2" RIB and another doel fin mounted on my Johnson 50 that is mounted on a 15 1/2 CC American Skiff. The up to plane on both boats has been dramatic to say the lease. There is no more porpiseing effect with the RIB. I've recommended the use of the fins to several friends and the results are positive with all those using them.
 
D

dilligaf

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Oct 18, 2008
45
Jeanneau 49DS Seattle
I had fins but all they did was skin my legs when the OB was on deck. I noted nothing different when I removed them. I think they are still on board, I will just set them on the dock where they might do something other than increase the weight on my boat!
 
sailormanbigd

sailormanbigd

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Jul 24, 2006
628
Legnos, Starwind, Regal Mystic 30 cutter, 22 trailer sailor, bow rider NEW PORT RICHEY, FL
I tried one and the only thing it did was slow the boat down from increased drag. I thought it would help get the aft end up and help the bow down but it didn't help. In theory it should work, but my exper was not good. Wasted my $ and drilled holes in my cav plate.
 
AXEL

AXEL

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Mar 12, 2008
359
Catalina C30 MKIII WEST ISLIP, NY
I have them on my 6 hp Johnson which is pushing my 9.5 Achilles . I love them. I've had them on for years. Without a doubt they have improved the up to plane performance as well as once I am up on the plane I can back off the throttle and maintain. My dink will plane with me and my wife combined weight 310 lbs plus 100 lbs for the dink with a 6 hp engine.
 
Brezzin

Brezzin

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Sep 20, 2006
155
Hunter 49 Mystic CT
I have them on my 9.9 and I did see great performance with them. However I now use a lehr 5. Hp and I won't bother with the fins. I believe the 5 just does not have the power to have the fins do anything but get in the way.
 
AXEL

AXEL

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Mar 12, 2008
359
Catalina C30 MKIII WEST ISLIP, NY
Brezzin said:
I have them on my 9.9 and I did see great performance with them. However I now use a lehr 5. Hp and I won't bother with the fins. I believe the 5 just does not have the power to have the fins do anything but get in the way.
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I originally had mine on a 5 hp Force and they definitely added performance. I moved up to the 6 hp Johnson only because I was having reliability issues with the Force (crap). The fins work well on both engines and show marked performance improvement. You can’t go wrong with these things.
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zeehag

zeehag

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Mar 26, 2009
3,198
1976 formosa 41 yankee clipper santa barbara. ca.(not there)
i used doel fins from 1996-2009, when i sold my last outboard fo dinghy planing.
i noticed no increase in hp, but i di d get more stability with the fins on and inuse. i used long shaft outboards. i noticed more ability to control th e squirrely tendencies i found came with the use of a longer shaft engine.
i noticed that with a short shaft 15 hp yamaha, that the fins kept the boat stable when , without the fins, my boat tended to be less reliably smooth in directionality. essentially, the fins threw the squirrel overboard. helped the prop dig into the water and plane the boat faster than without. not increased hp but much better performance.
 
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