Doel Fins on 20-25' Pontoon Boat?

[Karasu]

I know I'm dancing on the 'third rail' here by mentioning Doel fins, but I'm wondering if anyone out there has direct experience with Doel fins on a 20-25' 2-toon pontoon boat. Boat in question is a new to me 2008 SunTracker w/ a 90hp Mercury 2 stroke and lifting strakes. I've only had brief direct experience with the boat during the 'sea trial' but the boat seemed to want to 'squat' at the stern some and with the bow up at speed and not really level out even with the front half of the boat up on the lifting strakes. This even with various trim adjustments by the prior owner. Engine height appears correct. Boat ran great in all other aspects and could just be the nature of the beast. Any thoughts on the matter?

 

[ahicks]

About the most consistent thing I see with the use of ANY of those "whale tail" devices is for them to crack/break off large chunks of the cavitation plate they are bolted to. Those plates are NOT designed to be strong enough to have something like that bolted on to them. They WILL fail.

After that, usually you can solve issues like you describe with proper weight distribution. Some 'toons are equipped with large built in gas tanks in the engine pod or very back of the boat. Large enough to supply fuel for a month. Running around with a huge amount of extra fuel aboard doesn't help anything either....

 

[GA_Boater]

I wouldn't be basing anything on one sea trial. Use the toon some more before deciding something needs fixed.

The bow up attitude may have been the loading on that particular day. Experiment with passenger and gear placement.

 

[Sea Rider]

On flat calm no wind water cond check at which lower leg height is water flow passing at speed provided that trim is set at 90 deg and deck weight is evenly distributed, say sit 1-2 boaters up front, must not be sumo fighters though.

Check if flow skims right under upper small plate or over the AV plate and by how much to determine if the motor sits at the sweet spot height. If a doel fin doesn't ride parallel to water level once combo is at fast displacement or plane speed fin will achieve extra water drag that can slow the combo a bit, depends on the HP motor used. Fins are huge garbage collectors, nada bueno!!

Happy Boating

 

[harringtondav]

I agree with every comment above. Weight distribution adjustments are your best correction. Move your cooler and other dead weight gear forward. Spread your passengers out and forward.

 

[clemsonfor]

When i take the cooler out in the summer it sits up on the bow outside the fence. That puts say 50 pounds way up front. I just bungee the top down. it also serves as a small thing to hold it down a little more but if you go crazy and wake jumping etc it might fly off but i have a small rail that wraps around the front deck so it cant slide foward or off the side. The bungy is kind of a leash on it.

 

[5150abf]

More for a mono hull boat, don't think one would have a lot of effect on a toon.

I have run one on my fishing boat for years though