Offshore Fishing Hull Shapes

Design tips to help you pick a boat shaped for your passion

25th February 2011.
By Pete McDonald

The lecturer, a well-known boat builder, stood at the podium of the International Boatbuilders Exhibition (IBEX) and described his parameters for the perfect fishing cockpit. Where the fighting chair should be mounted, the square footage, the freeboard, how the cockpit door should swing, the washdown, everything down to the last detail. What an awesome lecture; I wish someone would do that for what’s underneath. Because an important part of what makes a good fishing boat is its running surface.

Hull shape affects a boat's ride and how it will behave while trolling.

Here are some thoughts I had on what I tend to look at in a boat hull, and what you might want, for running offshore.

Sharp as a Knife?
Excluding battlewagons, because they are beasts unto themselves with a whole different set of parameters, most people looking to run offshore key in on one important number. Whether it’s a center console, walkaround, or pilothouse, the angle of deadrise is an important indicator of how it will perform in waves. The deadrise at the transom is significant because, on a planing hull, only the aft end is consistently in the water. The steeper the deadrise, the better the hull can be expected to slice through waves. Some naval architects say a small boat needs at least 21 degrees of transom deadrise to qualify as a deep vee hull. Some of the best wave busters are as sharp as 24.5 degrees.

On a planing hull, only the aft end is consistently in the water, so transom deadrise is significant.

The deadrise is not the only aspect that will indicate how a boat will ride. Another is how the hull is shaped running forward to the bow. Boats with a sharp, narrow entry will be more likely to knife through waves than to pound. Also, take a look at a boat’s length centerline or waterline length (not its length overall) and compare it to the width of the boat. Boats with a 3:1 length to beam ratio generally cut through waves better.

Weight is another factor. Many builders are on an eternal quest to get lighter in the name of efficiency, but more weight can make for more solid footing in a rough sea. Weight also ties into construction. Boats with a stout build are less likely to pound, shudder and flex—and therefore less likely to beat you up in the process.

A classic Sea Craft variable deadrise hulshape

Flat as a Pancake?
There’s a reason every boat running offshore isn’t long and narrow with a super deep vee. Once you get to the fishing grounds, the skinny wave slicers tend to rock and roll. They are more susceptible to a beam sea while trolling or at anchor, rocking back and forth like a Weeble.

A flatter deadrise at the transom and a wider beam can make for more stability while trolling, drifting a reef, or anchoring up. Which is why you’ll see many boats in this category with a length to beam ratio closer to 2:1, and a transom deadrise between 18-22 degrees.

Boats with flatter running surfaces also need less power as they create less water resistance. So, theoretically, they can be more fuel efficient. But some of that also depends on weight and how the boat is loaded.

Another type of hull is the variable degree deadrise, which has a deep vee along the keel that flattens out in sections towards the chine. This is supposed to combine elements of both to make the perfect compromise. It gained popularity with the old classic Sea Craft hulls, but you don’t see as much of it today.

Catamarans ride on two separate, narrow hulls that slice through the waves.

Two For One?
Of course, the catamaran throws a wrench in evaluating small boat fishing hulls. Catamarans ride on two separate, narrow hulls that slice through the waves and, capped together with a wide deck, have the extra beam to provide stability. Some anglers swear they offer the best small boat ride for offshore running.

There are basically two types of cat hulls, the planing and the semi-displacement. Planing cats are faster and more buoyant, running on wider hulls, while semi-displacement cats are more efficient and tend to slam less (if at all) in heavy seas. The main drawbacks with cats are the outboard leaning sensation in turns, the tendency to snap roll while trolling or at anchor in a beam sea, and “sneezing” spray over the bow from between the hulls, leading to a wet ride. (For more info on power cats, read Power Cat Versus Monohull: Which is the Better Fishing Boat?)

So which one do you want? Depends on what type of offshore fishing you like to do. Are you going to run and gun or anchor and troll? Do you want rough-water handling or more stability at rest? Pick your poison, and then figure out your perfect ride.

Pete McDonald writes for Boating, Yachting, and other marine and fishing publications. In the past, he has written for Power & Motoryacht and Salt Water Sportsman, and spent 11 years on staff as a technical editor at Boating. All things considered, at any given moment he would prefer to be fishing.


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Pete McDonald

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Pete McDonald is a contributing editor to Power & Motoryacht. Previously, he spent 11 years on the editorial staff of Boating. He has won multiple writing awards and holds a master’s degree from the Columbia University Graduate School of Journalism.

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