Marissa Runabout

It seems that I never get enough time on outboard powerboats. I’ve always loved driving them for the simple wind-in-your-hair joy of it, especially when you can reach that out-of-the-way beach that often remains out-of-reach on a day off unless you have a fast boat. And anyway—shouldn’t everyone want to own a fast red motorboat at some point in their lives?

I think Graham Byrnes probably had just this sort of thing in mind when he designed Marissa, with a couple of further criteria: owning such a boat shouldn’t create hassles, and building it and running it shouldn’t cost an arm and a leg. Marissa’s promise of such simplicity — along with her undeniable fuel-efficiency — made the design the winner in the 2010 WoodenBoat Publications “Design Challenge” for new powerboat designs capable of sustained cruising at 15 knots using less than two gallons of gasoline per hour.

Benjamin Mendlowitz

Marissa was conceived as the smallest practical center-console runabout, and she became the winner of WoodenBoat’s Design Challenge for efficient small powerboats.

Byrnes, of B&B Yacht Designs in Vandemere, North Carolina, has a habit of blending speed, efficiency, and simplicity with strong aesthetic appeal in his sail and power boats. Any designer worth his salt would strive to make a design good-looking but also well suited to its uses, whatever they may be. Marissa delivers on both counts.

This is, above all, a stable boat, having the feel of a much larger one. Boarding and moving around the cock-pit have little effect on her trim. Her hull’s form stability is augmented by her stiff construction, which dampens the harmonic vibration Byrnes sees in other boats. So in addition to her solid feel, she has a remarkably smooth and quiet ride.

In heritage, she is a reduced version of Byrnes’s earlier North Carolina sportfisherman, the Ocracoke 20. But her function is not at all narrowly drawn. Marissa started as an intellectual challenge for Byrnes: Create the smallest center-console runabout practical. “You can always make a boat smaller,” he said, “but you can’t scale down people. It’s the smallest that is gracious and reasonable.”

The bottom panels reach 30 degrees of deadrise one-quarter of the hull’s length aft of the stem. At their top edges, the bottom panels culminate in chine flats, which give the hull a rakish look. Rising forward and tapering until they are flush with the bottom plank- ing only right at the stem, these flats accentuate the sheerline, which is already pleasing from all angles.

The chine flats are a handsome touch, but they are also practical, since they knock down spray forward and function very effectively as stabilizers while running. “And boy do they make it dry,” Byrnes said. “In whatever weather I’ve been in, it’s just dry as a bone. You can see how it’s really turning that water back down.” Powering in 4′ seas with four people aboard, he gave the boat a proper sea trial and found that she remained stable and dry. “That was running as hard as I could get it, even though it upset my ladies,” Byrnes said.

As a boatbuilder, if I like the looks and the lines of a hull, the next thing I do is take a close look at the construction drawings. I imagine myself building the boat in sequence and in as much detail as possible, and I ask myself whether the boat would be simple enough to make its construction practical yet challenging enough to keep it interesting. Marissa’s hull passes that test. Her construction is plywood throughout, using a conventional egg-crate-style framework of athwartships frames and bulkheads and longitudinal stringers, all of which are integral to the hull’s structure. With this framework set up for upside-down construction, the developable bottom and side panels are glued into place.

Benjamin Mendlowitz

Chine flats coupled with her hull form make Marissa a very stable boat, with sure handling whether the water is flat or choppy. Graham Byrnes (here at the helm beside his grand-daughter, Marissa, the boat’s namesake) designed the boat for a 25-hp outboard; here, he’s using a 30-hp four-stroke because he found the used motor for sale at a good price.

The chine flats may seem tricky to make on first glance, but on close examination I believe they would be simpler than traditional chine-log construction. Instead of chine logs, which typically require a lot of twist and rolling bevels for their lengths, this hull has chine battens for longitudinal stiffness. They are installed on the upper inner edges of the bottom panels, making their installation very simple, without bevels. Next would come the plywood chine flats, which butt against the top outer edge of the bottom panels and attach to the horizontal jogs in the frames and bulkheads — again, very simple to shape. After that, the topside panels would be fastened in place, flush with the bottom of the chine flats.

The joint would be radiused, assuring a better bond than a sharp corner would for the exterior sheathing of 10-oz fiberglass cloth set in epoxy. The joints between the chine flats and the bottom panels will be filleted with thickened epoxy and reinforced with fiberglass tape set in epoxy. Such joints — radiused on outside corners where sheathed, filleted and taped on inside corners — are used uniformly throughout the hull to reinforce the structure. For the structural elements that double as the components of the building jig, the plans, which are very neatly drawn, include full-sized patterns. A kit consisting of these components precut by CNC (computer numerically controlled) router is also available.

The rest of the hull construction would be straightforward work, the only complications being the installation of a pipe chaseway under the cockpit sole to carry steering cables and wiring; the installation of a fuel tank under the console, which has a fill tube on its starboard side; and filling chambers on both sides with flotation foam before installing the cockpit sole. All these details are clearly specified and easy to follow in the plans.

The center console as designed is functional, and the seat is comfortable for the driver and a single guest. Flip-up seats in the quarters provide a place for more guests to sit. I suppose similar side seats up forward might well serve the same purpose, if guests are often along for the ride and if other intended uses — fishing, for example —can tolerate such intrusions.

The console itself provides opportunities for individual choice, for example in the selection of a GPS with a large display. There’s ample room for, say, a fishfinder, as well, along with a VHF radio and other gear left to the imagination and personal preference. Byrnes added a tachometer and a fuel gauge and left it at that.

Tom Jackson

This partly-finished center console provides ample room for whatever the owner wishes to install. A fuel fill is inset on the starboard side.

For power, Byrnes specifies an outboard motor of between 25 and 60 hp, matching the light weight of the hull. Her fuel consumption statistics are based on the 25-hp model, with which she reportedly can achieve 15 statute miles per gallon. That motor’s top speed of 21 knots puts fuel consumption at 2.2 gallons per hour. Byrnes found the measured results very close — and slightly better — than predicted. Running at 5,900 rpm, she hit a top speed of 22 knots, and with the motor trim fine-tuned she reached 22.5 knots, half a knot above projected top speed. “I was tickled to death,” he said. “That’s what we wanted and that’s what we got.”

For those results, Byrnes used a 30-hp Suzuki four-stroke when he brought Marissa to WoodenBoat’s waterfront in July 2010, while he was teaching design at WoodenBoat School. That motor, which he bought secondhand and whose installation he was still tweaking, seemed perfectly fine to me: the boat is pleasantly responsive, maneuvers easily, accelerates well, turns handily, and planes readily. His outboard came without a power tilt trim, and that’s one thing Byrnes recommends adding, not only for easily raising the motor while nosing into shallows but also for making minute adjustments for greater efficiency under way. “That would really be at the top end of my wish list,” he said.

Byrnes said that when he designed the boat, he had the Design Challenge rules in mind but also wanted something that would be marketable in his area, which he calls “center-console country.”

“Having used most layouts, I can really see that center console is the best choice: it’s so easy to get around the boat, you can do anything. Being able to quickly get to any part of the boat just makes sense, and visibility is very good. I didn’t think I’d win, but I felt that at the very least I’d have an excellent, salable, marketable project.” He also knew that many would want more power — “you can never overpower a boat for the American market,” he said. He wanted a hull that could take more power if asked to. Cruising at 15 knots using a little more than a gallon per hour “exactly suits me,” he said. “That’s exactly where my mental outlook is.” But the question he is most often asked is whether the boat can take a bigger motor.

Marissa, B & B Yacht Design’s winning entry in the 2010 WoodenBoat Publications “Design Challenge,” is economical to build and use. A stepped chine gets the boat on plane quickly; the center-console layout is conventional but efficient; the lines show a boat that moves easily through the water at displacement and semi-displacement speeds.

More power might be tempting to some, but that would come at a cost, not only in the cash outlay for the motor itself but also in fuel consumption. For me, 15 knots or so is a very civilized speed to watch the world go by, rewarding the driver with a quiet, smooth, and enjoyable day on the water. Plus, you can still enjoy an actual conversation with the person with the wind in her hair.

To read another perspective about the Marissa Runabout click here.

Check Out These Other Runabout Designs!

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A 17′ Outboard Runabout – Paul Gartside’s Design #221

Runabout 14 – A plywood speedster from Bateau.com (now located at boatbuildercentral.com)

Lyman Runabout – A 1950s classic in lapstrake plywood