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Author Topic:   added fin on cavation plate
dauntlass 18 posted 05-18-2001 09:17 AM ET (US)   Profile for dauntlass 18   Send Email to dauntlass 18  
I could use some advise on adding a Dole fin to cavtation plate on my 21ft. Conquest the engine tops out @5200 I am told this is ok & correct max rpm.My problem is 2000 to3000rpm range boat bogs down engine seams to labor.I know all boats have a rpm setting where they hang before going on plane.Would add on fin reduce this condition?The engine is optimax 200hp the prop is mirage three blade no trim tabs on boat.
kingfish posted 05-18-2001 10:46 AM ET (US)     Profile for kingfish  Send Email to kingfish     
Simple answer is yes; based on the experiences I have had with Doel fins (three different boats from 13' to 22'), I believe you are certain to enjoy at least some noticeable change. As you know, or will know, Doel fins are pretty inexpensive, and if you don't get enough difference with them installed to make you happy, the next step is trim tabs, and you would not have thrown away many dollars.

Good luck-

kingfish

lpaton posted 05-18-2001 01:14 PM ET (US)     Profile for lpaton  Send Email to lpaton     
Doel fin reduced speed at which my boat would plane. Added it last day of season last year so info is preliminary and boat was loaded.
OutrageMan posted 05-23-2001 08:06 AM ET (US)     Profile for OutrageMan  Send Email to OutrageMan     
Last season I added the Stingray Hydrofoil to my 22' Outrage WD w/250 Yamaha V-x.

Torque list was eliminated, very fast to plane, plane at lower speeds, more useable trim range, better hold in tight turns.

Bob D posted 06-07-2001 10:46 AM ET (US)     Profile for Bob D  Send Email to Bob D     
Concider going with the one piece Whale Tail if the fins are the way you want to go. I have a "96" 19 Outrage with a 200hp Johnson. The boat without fins would stand straight up on hole shots. I installed doel fins and it seem to help a lot. A friend was telling me that he had tried the doel fins and then tried the one piece Whale Tail on his boat. He said the Whale Tail was better on his boat. I went out and bought one and it made a big difference. I was able to still plane at around 2900rpms with the Whale Tail where the doel fins were only giving me a plane at 3200rpms. If I tried to go lower then that I would get a surging at any trim angle as if it was wanting to plane but was just on the verge. The Whale Tail seems to give more stability also. I'm now cocidering putting trim tabs on. The One thing that you need is to be able to adjust the loads from port to starboard when you have unbalanced loads or in windy conditions. The tail and fins wont do this. For around $400. you really can't beat trim tabs. The other thing I heard but don't hold me to it was: If you install fins on the cavitation plate on the outboard manufactures can void your warranty.
lhg posted 06-07-2001 02:36 PM ET (US)     Profile for lhg    
On a boat as heavy as a 21 Conquest, with a high weight to length ratio, I would think that trim tabs would be a better solution to your problem.
dauntlass 18 posted 06-07-2001 07:44 PM ET (US)     Profile for dauntlass 18  Send Email to dauntlass 18     
I installed a SST Hydrafoil model b on engine it helps out in 2000 to 3000 rpm range.I have not used it long enough to really give a good opinion.It does get boat on plane sooner& at a lower rpm setting.IHG thought on tabs is probably best way to go.Thanks for all the input on fins.
OutrageMan posted 06-10-2001 07:34 AM ET (US)     Profile for OutrageMan  Send Email to OutrageMan     
Bob,

Adding these fins does not viod any of the warranty.

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