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  Do [Doelfins] Reduce Top Speed?

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Author Topic:   Do [Doelfins] Reduce Top Speed?
timbo posted 06-24-2002 09:24 PM ET (US)   Click Here to See the Profile for timbo   Click Here to Email timbo  
[This topic was originally posted to the GENERAL FORUM. This thread has been edited--jimh.]

[I] have read...that [Doelfins] actually lower your top end a couple of miles an hour, although on another discussion I read all good things about them. I plan on installing them on my 1973 13-Sport. Any follow up would be appreciated.

JBCornwell posted 06-24-2002 09:59 PM ET (US)     Click Here to See the Profile for JBCornwell  Click Here to Email JBCornwell     
Hi, Timbo.

I water tested my Montauk with her new Suzi without a fin to select the prop. 38.5mph at 5800rpm.

I added a SE Sport 300. Planes at lower speed, doesn't raise the bow, just rises onto plane. 38.5mph at 5800rpm.

I recommend the SE Sport 200 or 300.

Red sky at night. . .
JB :)

bsmotril posted 06-24-2002 10:16 PM ET (US)     Click Here to See the Profile for bsmotril  Click Here to Email bsmotril     
Speed loss will depend on whether or not your cav plate rides above the water, or under it at top speed. Have someone else run the boat at top speed while you peer over the transom and CAREFULLY observe the cavitation plate. If it is riding out of the water, a fin will probably not bring down your top speed. Make sure to trim the motor out for max speed while doing this.
acseatsri posted 06-24-2002 08:56 PM ET (US)     Click Here to See the Profile for acseatsri  Click Here to Email acseatsri     
If your main goal is to go fast, I wouldn't install one, as I've heard from others that they scrub 2-3 mhp off your speed. If you want to cruise more comfortably and keep the bow down to avoid "porpoising" at lower speeds, install one.
Clark Roberts posted 06-24-2002 09:26 PM ET (US)     Click Here to See the Profile for Clark Roberts  Click Here to Email Clark Roberts     
I use Doel-Fins on all my boats and set the engines high (most on jack plates) so that fin is riding just on surface of water at speed... thus no fin in water and no loss of speed. Most engines are set up low on transom and drag of lower unit robs top speed and economy... one must be sure cooling water pick-up/flow/pressure is not compromised by getting up too high! I also run temp and press gauges... Happy Whalin'.. Clark.. Spruce Creek Navy
FISHNFF posted 06-25-2002 01:27 AM ET (US)     Click Here to See the Profile for FISHNFF  Click Here to Email FISHNFF     
I have a Doel Fin on a Merc 90 4S mounted on the third hole up. No loss of top end at all, as the fin is riding out of the water at speed.


jimh posted 06-25-2002 04:57 AM ET (US)     Click Here to See the Profile for jimh  Click Here to Email jimh     
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