Doel Fins

[SiDfish]

Hi All

I've got doel fins on my 15hp Yam.  They really do push the stern up from a standstill and give stability at speed.  I have seen people call them dangerous here and a couple of other places, why?  I've had great service from them on twin 70s, 90s and 225s, a single 15, 25 and 40.

[Saintly Fish]

Aren’t they purely to try and prevent porpoising? I remember my raider that @PompeyDave now owns had them. I found that just better weight distribution helped more. 

[Andy135]

For me, it's the thought that if they really worked as suggested then they would come as standard from the outboard manufacturers. Happy to be proved wrong, but the development budgets and brainiacs of Honda, Yamaha, Suzuki etc are unlikely to have missed a trick.

[PompeyDave]

38 minutes ago, Andy135 said:Exactly my thoughts. Funnily enough Argonaut (saintlyfish’s Raider is now called) porpoises quite badly. I’m not too worried as I’ve only been out on it three times and I’m still getting used to the boat. I have wondered whether trim tabs might help?

[PompeyDave]

Exactly my thoughts. Funnily enough Argonaut (as saintlyfish’s Raider is now called) porpoises quite badly. I’m not too worried as I’ve only been out on it three times and I’m still getting used to the boat. I have wondered whether trim tabs might help?

Edited December 11, 2020 by PompeyDave
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[Saintly Fish]

2 minutes ago, PompeyDave said:

Exactly my thoughts. Funnily enough Argonaut (as saintlyfish’s Raider is now called) porpoises quite badly. I’m not too worried as I’ve only been out on it three times and I’m still getting used to the boat. I have wondered whether trim tabs might help?

I just sat the anchor and rode bucket as far forward as possible to keep the nose down. It seemed to work. You could look at the engine height too. 

[Andy135]

32 minutes ago, Saintly Fish said:

I just sat the anchor and rode bucket as far forward as possible to keep the nose down. It seemed to work. You could look at the engine height too. 

Yep. I've heard the same. Moving weight forward is recommended to help with porpoising.

[Andy135]

46 minutes ago, PompeyDave said:

Exactly my thoughts. Funnily enough Argonaut (as saintlyfish’s Raider is now called) porpoises quite badly. I’m not too worried as I’ve only been out on it three times and I’m still getting used to the boat. I have wondered whether trim tabs might help?

Before trim tabs, try moving as much weight forward as you can. Even consider adding some weight if it helps to keep the bow down.

[JDP]

You only find how dangerous they can be in conditions you would rather not find how dangerous they are. When you are pushing to get home in big seas and find yourself taken side on by swell and the fins exaggerate the motion and hold you on your side you will need to react fast in order to not turn the vessel over. You can expect this continually if you are being hit by the right sized waves from a certain angle. The only boats Ive ever left them on after buying a secondhand boat have been boats to be used in calm conditions ( river and estuary boats).

Self leveling tabs are about the same money and don't seem to have this same effect of holding the boat at extreme tipping angles. Over here fitting fins to outboards voids the outboards warranty, many outboard mechanics claim they also put unnecessary pressure on the pivot areas where the engine turns. Ive seen many engines where the plate they have been attached has cracked or broken from people using them as a step to get into their boats. In saying that you dont very often see them being used on offshore trailer boats anymore here as people have had bad experiences from them ( including me ).

[JDP]

9 minutes ago, JonC said:

I have zero experience of them but as @Andy135said earlier if it was that easy the manufacturer would just build them into the engine you would think. 

Totally agree and the fact they don't recommend using them speaks for itself. People need to ask outboard manufacturers, not dealers who sell fins. 

There are also other ways that can help with trim issues, such as outboard wedge plates that allow an outboard to be trimmed in more but these are not needed to often. As most boaters will know, an engine trimmed in to much in big following seas is not going to handle well. 

[GPSguru]

3 hours ago, SiDfish said:

Hi All

I've got doel fins on my 15hp Yam.  They really do push the stern up from a standstill and give stability at speed.  I have seen people call them dangerous here and a couple of other places, why?  I've had great service from them on twin 70s, 90s and 225s, a single 15, 25 and 40.

Yes, they work on some boats but not others ............... I had them on my Shetland 570 with a Johnson 70, and they worked great, but I have been on other boats where doel fins have made the handling more than a little 'iffy'

The problem occurs as you go into a turn under power and the stern 'digs in' causing the boat to take on quite a pronounced and sudden list to port or starboard, backing off the throttle and less steering input fixes the problem, under those circumstances the boat feels quite unstable as the 'shift' is very sudden and pronounced ....................

It doesn't happen to all boats, just some ..................

 

[mick]

When we had Explorer Elite it porpoised like the 165s ,fitted smart trim tabs ,problem solved,faster on to plane .

[MegaByte]

6 hours ago, mick said:

When we had Explorer Elite it porpoised like the 165s ,fitted smart trim tabs ,problem solved,faster on to plane .

Same as Mick, I've Smart Tabs on my 165. I played about with the settings, now very happy.

[SiDfish]

Looks like I'll be fine with them on the Quintrex, used in small bays and/or calm conditions.  I'm happy with the extra lift they give and have no directional probs.  Auto trim tabs?  This one's got tiller steering!