Classic Whaler Forum
Classic Whaler: Performance
Do [Doelfins] Reduce Top Speed?
|Author||Topic: Do [Doelfins] Reduce Top Speed?|
posted 06-24-2002 09:24 PM ET (US)
[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.
posted 06-24-2002 09:59 PM ET (US)
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. . .
posted 06-24-2002 10:16 PM ET (US)
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.
posted 06-24-2002 08:56 PM ET (US)
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.
posted 06-24-2002 09:26 PM ET (US)
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
posted 06-25-2002 01:27 AM ET (US)
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.
posted 06-25-2002 04:57 AM ET (US)
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