Outboard Planing Fins

[Boatguy30]

Have used the 2 piece Davis plastic fins in the past, but wondering if there are better options like some of the one piece alloy ones?

I have a 1977 .evinrude 9.9 on a Caribe C-9. The stern REALLY squats when trying to get on plane and with only about 320 in crew weight it struggles to get fully flat when planning. With around 200 lb of crew weight it is quite fast.

Might need a different prop and 15 hp carb as well.

[colemj]

We had the Doelfins on several previous outboards and have the SE Sport200 on our current outboard: Amazon.com : SE Sport 200 Hydrofoil, fits 8 hp - 40 hp engines : Boating Equipment : Sports & Outdoors

I think the SE may perform better, but it is difficult to judge because it is on a completely different engine. It definitely is less cumbersome when moving the engine around off the dinghy and catches less weeds.

There are other types that look like an entire re-engineered lower unit, but I don't know how they work. Seems like the best thing would be to get a new larger outboard before bolting on those expensive contraptions.

However, I think you are expecting WAY too much from a 1977 Evinrude 9.9 on a Caribe C-9 with 320# of crew.

Mark

[MarkJ]

1977? My grandmother is younger.


Get the fins but a coffin may be better.

[Boatguy30]

She runs sweet. A very low hour fresh water motor. I'm planning a big joint birthday party for 2017 perhaps in Musket Cove. Just pulled the Caribe from the trash Thursday so hard to say if that'll make it, but only needed 2 patches so far.

I'd go on, but I'd sound even more WT.

[Boatguy30]

Just ordered a stingray jr "new" off eBay for $21, free shipping. Will see how it does. Considered the SE 200 but saw some posts on fishing forums they work best on 20 horses plus. They probably all work the same roughly on this application. Will keep a lookout for another junky caribe with 37 y/o motor to speed test with.

[sparrowhawk1]

Originally Posted by Boatguy30

Just ordered a stingray jr "new" off eBay for $21, free shipping. Will see how it does. Considered the SE 200 but saw some posts on fishing forums they work best on 20 horses plus. They probably all work the same roughly on this application. Will keep a lookout for another junky caribe with 37 y/o motor to speed test with.

What words did you use for your search? Thanks.

[Roy M]

I purchased a Davis Whale Tail, the aluminum unit, for my propane Lehr 15, on an AB RIB, but haven't had time yet to install it. I plan on putting it on temporarily, removing it and doing a measured mile a couple times, then, the same day, pop the Tail on and do a comparison. Should be interesting.

[sparrowhawk1]

I just ordered 1 ( hydrofoil by shoreline marine) on amazon for $15.60 searched outboard hydrofoil and on the lower priced ones "searched" buying options and I got one used- free shipping but I had to join Amazon Prime(for free)

[Boatguy30]

The stingray seemed to make a very small difference. It does keep the stern from squatting as much going on and coming off of plane but make little difference if any as far as the time to get on plane.

In hindsight, this was pretty much my experience with the Davis fins in the past. I think they only really help when you have a marginal planning setup it can maybe give you that extra little bit. But certainly does not make anywhere the difference the companies claim.

[Captain Bill]

I put the Sting Ray Jr. on my 15 hp Suzuki and my 10'4" Achilles Rib. It didn't make very much difference with two people on board, but it made a huge difference with one person on board. With only one person on board the RIB would squat and the bow would come up extremely high. You actually had to give it power very slowly and it took a while to get the bow down and the boat on a plane. With the Sting Ray Jr. It pops up on a plane very quickly. It also stopped some air entrainment I was getting around the prop when trying to get on a plane in choppy water. I don't think it did anything for me as far as top speed goes, and it may have even cost me a little. It has to add some drag that wasn't there before.

[sparrowhawk1]

Originally Posted by sparrowhawk1

I just ordered 1 ( hydrofoil by shoreline marine) on amazon for $15.60 searched outboard hydrofoil and on the lower priced ones "searched" buying options and I got one used- free shipping but I had to join Amazon Prime(for free)

Installed my fin made a huge difference. I have a dinghy that is basically a sailboat, 10 foot long with an 8 horsepower on it and just above idle throttle it would start squatting. Now it stays flat and I can go fast but I'm not sure it's truly planning. I ordered one for my friend and the price went up to 19.19 after tax. But well worth it. And they're listed as used but they're brand new with a very slightly damaged box

[rourkeh]

If these fins on the lower unit actually worked don't you think the outboard manufacturers would have incorporated them into their lower units to make them perform better? Funny that not a single company produces an outboard with a finned lower unit!!!!

[Dockhead]

Originally Posted by rourkeh

If these fins on the lower unit actually worked don't you think the outboard manufacturers would have incorporated them into their lower units to make them perform better? Funny that not a single company produces an outboard with a finned lower unit!!!!

But they do work.

I installed a large set on my 25 horsepower Mariner, and the dinghy now planes at about half the RPM as previously, giving a far more economic and comfortable cruising speed. Vast difference, at least on my boat.

[GordMay]

Originally Posted by rourkeh

If these fins on the lower unit actually worked don't you think the outboard manufacturers would have incorporated* them into their lower units to make them perform better? Funny that not a single company produces an outboard with a finned lower unit!!!!

A very good question.
Perhaps (tho' I doubt it) a patent issue?

* Or offered them as an OEM accessory.

[belizesailor]

Originally Posted by rourkeh

If these fins on the lower unit actually worked don't you think the outboard manufacturers would have incorporated them into their lower units to make them perform better? Funny that not a single company produces an outboard with a finned lower unit!!!!

Yeah, you would think, but clearly such behavior does not hold in the actual market place. Take just about any complex thing you buy (motors, boats, cars, computers, cell phones...) and there is significant after market accessories business (cell phone accessories is a massive market for example).

The OEM lower units are finned enough to prevent cavitation and these after market fins do make a difference. I've run the same engines on dinghys with and without and the difference is very apparent. The main advantage from my perspective is much quicker planing.