Doel Fins, what an improvement!

[jibstay]

I have a Highfield CL 340 with a Yamaha 25hp 4-stroke.

I recently installed the Doel Fins. Might be the best $28 I ever spent.

Huge improvement, especially getting up on a plane by myself.

[OldManMirage]

I have found that putting a set of fins on the lower unit of any boat I've had to be an improvement, either outboard or an I/O unit. Up on a plane quicker and you can stay on a plane at lower speeds. It makes me wonder why they come that way !!

[tkeithlu]

You are trading some drag for some lift. In the case of a marginally underpowered rig, that's a good trade - you need more lift more than you need top end speed. On a marginally overpowered rig, it's not a good trade because you can easily get up on a plane and don't need to sacrifice speed. Lots of outboard rigs are overpowered. You are maginally underpowered, and have tailored your lift to your hull and weight. Good work, but it does not imply that all engines should come that way when the manufacturer doesn't know how they will be mounted.

[GordMay]

Originally Posted by tkeithlu

... Good work, but it does not imply that all engines should come that way when the manufacturer doesn't know how [or on what] they will be mounted.

Indeed.

[Shrew]

Make sure to crank down on the mounting screws. Boats are designed to plane from lift on the hull. You're adding lift on the outboard, which is creating upward force being transferred to the transom by the mounting screws. The marriage of the outboard to the transom wasn't really designed for this.

Yes, they work just fine, but keep in mind what is going on here. If the OB is permanently mounted, consider bolting it. Otherwise, consider reefing the screws and checking them periodically.

[jibstay]

Originally Posted by Shrew

Make sure to crank down on the mounting screws. Boats are designed to plane from lift on the hull. You're adding lift on the outboard, which is creating upward force being transferred to the transom by the mounting screws. The marriage of the outboard to the transom wasn't really designed for this.

Yes, they work just fine, but keep in mind what is going on here. If the OB is permanently mounted, consider bolting it. Otherwise, consider reefing the screws and checking them periodically.

Good point.

I have the FCT steering console and seat, so my outboard is thru-bolted on.

[ranger58sb]

Originally Posted by jibstay

I have a Highfield CL 340 with a Yamaha 25hp 4-stroke.

I recently installed the Doel Fins. Might be the best $28 I ever spent.

Huge improvement, especially getting up on a plane by myself.

Originally Posted by jibstay

Good point.

I have the FCT steering console and seat, so my outboard is thru-bolted on.

I'm surprised the 25-hp outboard might struggle. What circumstances? Does "by myself" mean only you aboard? or how many pax, total weight, etc?

I'm in the process of negotiating a CL340 with the "GT" console, but don't want to go above 20-hp. And instant planing isn't all that critical for us... but your experience is interesting.

-Chris

[thinwater]

The problem is that a deep V-bottom does not provide planing surface, and the fins help. It's not so much power as surface. it only takes about 3-4 HP to plane a flat bottom dinghy with one passenger.


A deep V gives a smoother ride, but there is a cost.


Highfield CL 340




It lacks the chimes that every deep seas hull has. Also no flatter sections aft. Not a hull design that would go on a "real" boat because it won't plane efficiently.

[Siberian Sea]

Back home I did the same thing on a 17ft skiff I own. I bolted a fin system by the name of Stingray to my 50 hp outboard and immediately noticed the skiff on step faster with lower rpm with less fuel consumption. In heavy chop there is less cavitation

[rslifkin]

The other time I could see a fin helping is with a single person in a non-console dinghy. That usually leads to being very stern heavy, so adding more lift aft from a fin may help it settle onto a nice plane at an appropriate running angle vs struggling along with the bow in the air.

[pcmm]

Originally Posted by jibstay

I have a Highfield CL 340 with a Yamaha 25hp 4-stroke.

I recently installed the Doel Fins. Might be the best $28 I ever spent.

Huge improvement, especially getting up on a plane by myself.

That's a steal of a price for a stabilizer for an outboard!!! They work great. Where I am they are all in the $85 range but well worth the cost!