BOAT REVIEW Tristram 641 Offshore

August 2018 Trailer Boat Reviews
Words: John Eichelsheim. Photography: Bryce Taylor
Build Quality
MODEL Tristram 641 Offshore
DESIGNER Triistram Marine
BUILDER Tristram Marine
LOA 6.4M
BEAM 2.42M
ENGINE Mercury 175hp V6 four-stroke
Weight on Trailer 1700 kg
Length on Trailer 7.35M
Height on Trailer 2.2M
Max Horsepower 225hp
Passenger Capacity 4 people
DEADRISE 22 degrees
  • Rides and handles like a much bigger boat
  • instant throttle response and excellent control
  • Punchy V6 Mercury a great match for the 641 hul
  • Fit and finish to Tristram Marine’s usual high standar

The new 641 Offshore is Tristram Marine’s smallest ‘blue water’ model, pitched very much at the sport fishing market. It’s an updated version of the boat we first reviewed in 2011.

The sweet-riding hull remains unchanged, but the deck moulds have been modified to push the helm position forward to increase cockpit space, the dashboard has been upgraded and there’s an improved anchor locker.


The Tristram 641 Offshore can now accommodate a Maxwell RC8 capstan, though an RC6 is big enough for most anchoring duties, and the re-designed helm console is big enough to accept a flush-mounted 12-inch multi-function display (MFD). Tristram Marine has also made generous use of SeaDek on the cockpit sole, which not only looks great, it is comfortable underfoot.
But the biggest difference between this boat and the boat I reviewed seven years ago is the outboard. Tristram Marine now works with Mercury as well as Yamaha and this boat has one of Mercury’s exciting new lightweight V6 four-strokes bolted to the transom.
Mercury’s new V6 outboards feature a large capacity 3.4-litre, 24-valve, DOHC powerhead, which furnishes heaps of torque. The V6 weighs only 215kg and comes in 175hp, 200hp and 225hp variants; this boat has the 175hp engine with mechanical controls – Mercury digital controls are an option – and hydraulic power steering.

This was my first opportunity to try one of Mercury’s new V6 engines and I’m impressed, not only with the power delivery, but also with Mercury’s Adaptive Speed Control, which maintains engine revolutions regardless of sea conditions or helm inputs.
Load up the engine by putting the boat into a hard turn or punching through a wave and engine revolutions remain steady – there’s no need to touch the throttle. This is a useful feature, especially when it’s a bit rough or when trolling, because the boat maintains a constant speed.
The 641 has a conventional layout with 1.8m v-berths/seating in the forward cabin, provision for a toilet under the middle cushion and a good-sized hatch through which to access the bow. The Maxwell capstan and anchor locker are neatly tucked away under a moulded GRP cover.

The king and queen-style back-to-back seat bases both sides are part of the deck mould. They combine generous padding with extensive under-seat storage. It’s a large cockpit for a boat of this size – 1450cm long, in fact. The 641 Offshore was developed from the well-regarded Tristram Avant Garde, one of the company’s most popular models with hundreds of owners, but the 641 Offshore’s new deck moulds were configured for fishing.
There’s a good-sized underfloor wet locker in the cockpit (twin hatches and deep, moulded drains), moulded side shelves, rod storage under the padded gunwales, and two angled stainless steel, through-gunwale rod holders per side. The teak covering boards are a nice touch and there’s LED cockpit lighting for night fishing.

Moulded bins either side of the outboard well can be used for bait or live bait and a pair of transom hatches provide space for a washdown hose or additional dry storage. A removable ski-pole accommodates a bait table with additional rod storage and a drop-in insulated fish bag is an option for the underfloor locker. The extendable boarding ladder is on the port side.
As always with Tristram Marine, the batteries – house plus start – and battery isolation switch are well-protected inside the curved transom locker. The cabling and hydraulic hoses to the engine are extremely tidy.
SeaDek is easy to keep clean – simply hose it off or scrub it with a soft brush if it becomes really soiled. The cockpit drains into the bilge via scuppers in the cockpit sole either side of the outboard well, where a 1100gph bilge pump, also accessed via the transom locker, sends it back overboard.

In our climate a bit of shelter is always welcome. Tristram Marine’s well-engineered targa top offers some respite from sun and rain, as well as a five-position rocket launcher and, with the addition of optional clears, it can provide decent all-weather protection too. A backdrop cover’s also available. The targa folds to facilitate garaging and road trips. A road cover is standard.
I found the helm position very comfortable, even though there’s no seat adjustment. The footrest is the right height for me when sitting down and the curved glass windscreen does a good job of keeping the wind of passage off the face, also when standing up to drive.
The 641’s sculpted dash accommodates a full complement of six Mercury gauges under the anti-glare carbon-look eyebrow, while the main part of the console is big enough for a flush-mounted 12-inch display, though the test boat makes do with a nine-inch model. Trim tab controls, the ignition/start key and a switch panel find space either side of the wheel, while the VHF radio is mounted low down below the throttle lever.

The new Mercury 175hp is a really good match for this sweet-handling hull. It’s a lightweight engine – lighter than Mercury’s DFI Optimax two-stroke – and the excellent power-to-weight ratio enhances the boat’s nimble, safe handling.
The Tristram rides like a much larger boat, easily mastering the Waitemata’s typically short, steep chop and delivering a comfortable and quiet ride. It feels great to drive, relishing plenty of throttle and showing impeccable manners in a following sea. No wonder Tristram Marine stuck with the Avant Garde hull. Why change a well-proven design?
The torquey nature of the new Merc is most evident in the way the 641 pops up onto the plane, but also in the way it holds the plane at lower speeds. This is a reasonably deep-vee hull, but it planes at just 12 knots with this engine.
The combination of torque and horsepower provide instant throttle response and excellent control, which is what you want when negotiating rough water or crossing bars.

Best performance on the day was a top speed of 76.5kph (41.3 knots) downwind with similar performance figures upwind. At a cruising speed of 25 knots, fuel burn was a modest 24 litres per hour; at 30 knots it was 32lph.
The Tristram 641 Offshore is supplied on a premium quality dual-axle Enduro trailer, with over-ride brakes on one axle, multiple rollers and an integrated freshwater flushing system to extend trailer life. As you would expect from a Tristram boat, the 641 Offshore is strongly constructed, well-finished and carefully detailed, even if it’s not the highest specced model in the Tristram Marine range.
Best of all, it performs and handles like a much larger boat, easily living up to its Offshore moniker.