July 24, 2020

Building A Better Fuel System


Northern Marine Knows Its Priorities

By: Bill Parlatore

As I continue to follow the construction of Northern Marine’s newest 57-foot yacht, I had the opportunity to discuss some of the engine room details with Stuart Archer, Northern Marine’s general manager, and production manager, Randy Stoneman. The Northern Marine crew plan to put the deck superstructure on the hull (5706) next week and are busy with the many details necessary before that can happen. Furniture modules and other large components need to go into the boat before the deck goes on.

I was particularly interested in learning about the new yacht’s fuel system, especially given both Stuart’s and Randy’s experience with commercial boats and big yachts. Stuart once told me the problem they face is fitting big-boat mentality and systems into smaller expedition yachts. It is the opposite from most pleasure boat building, and that fascinates me.

As I asked a few questions about fuel systems, Randy began with the basic issue of transferring fuel into a big boat, which is handled differently from what we experience in typical pleasure boating.

On large yachts and commercial boats, with fuel tank capacities of 6,000 to 10,000 gallons, it is simply not an option to come alongside a fuel dock and have the dock attendant hand you a fuel hose nozzle. These big boats take on fuel at commercial facilities or where tanker trucks can reach them. They use Cam-Lock fittings to lock onto the boat’s fuel fill and fuel is pumped under pressure at transfer rates of many hundreds of gallons per minute. To move this amount of fuel safely yet quickly, operators must use extreme care to coordinate and control the process at the boat’s transfer manifold, and fuel tank venting is daisy chained to keep the high-speed transfer going smoothly. No pressurized geyser of a “burp” out a vent from overflow is acceptable.

Fuel manifold of previous NM-5705.

As Stuart was quick to point out, refueling big yachts with large fuel capacities obviously does not happen very often, especially expedition trawlers that carry enough fuel to go halfway around the world.

There are three tanks on 5706. Two saddle tanks in the engine room each hold 950 gallons, and there is a third tank located forward under the guest stateroom that holds 560 gallons. Stuart said they are not setting up this boat to use Cam-Lock fittings, as it is not necessary for a smaller expedition yacht that will go cruising, not fishing for months in the Bering Sea.

New saddle tanks on NM-5706 with fittings down low.

Similar but Different

Randy explained that since each Northern Marine yacht is unique, built to accommodate the desires and needs of its owners, the builder doesn’t work off carefully drafted schematics for systems as one expects to find in a production boat building operation. Even so, the experienced team knows all the required components, and what needs to connect with what. So, all systems, such as the fuel system, are developed and installed as the boat comes together. There are obviously many similarities from boat to boat, but everyone looks to see where it can be done better or use newer materials.

An owner might want his new yacht to include a superb Alpha Laval fuel polishing system from Sweden, for example, which costs an additional $30,000. This premier centrifuge fuel polishing system is the best of the best, but somewhat overkill for the kind of cruising most Northern Marine owners plan to do. However, bad fuel is not always assured no matter where one travels, so a quality fuel polishing system is standard on all Northern Marine yachts. The company has had great results with well-engineered systems from companies such as Parker Hannifin.

The fuel tanks are tested to 2psi and in addition to sight gauges, the builder installs Maretron transducers on the bottom of each tank to measure pressure of the fuel column accurately and convert it to fuel levels electronically.

When a new boat is complete, and ready to take on fuel for the first time, a fuel truck comes to the Anacortes yard, and fueling begins. The trucker is instructed to pump out precisely one hundred gallons, then stop. Crew in the engine room carefully mark the sight gauges and calibrates the electronics, as necessary. Then another hundred gallons goes into the boat, and the process is repeated until each tank is full. This only needs to be done once for a new boat and is the most accurate way to know without question what the fuel capacities are and specific fuel levels regardless of the shape of the tanks.

Craftsmen Quality
The fuel lines on all Northern Marine trawlers are custom made by the builder using 316 stainless steel tubing. With a fully equipped shop in-house, the stainless tubing is precisely shaped to fit perfectly and connect manifolds, valves, filter assemblies, and other connections in the engine room.

This brings up an important point about fuel line connections. I have been on too many boats where the boat builder used plumbing pipe fittings to make fuel line connections, especially on fuel manifolds where all the fittings are lined up neatly. It is an illusion of quality.

Pipe fittings are tapered and seal by thread deformation. They are not reusable, but much more importantly, they are not positionable. That means when the pipe fitting is properly tight it is not likely pointing in the right direction. So, the builder unscrews the fitting enough to face the right way and relies on thread sealant to prevent leaks. Look at any manifold where all the pipe fittings are facing the same direction, and I guarantee you none of them are tight.

Northern Marine uses the vastly superior connections offered by metal-to-metal JIC flare fittings on any short hose whips placed on the ends of stainless steel tubing when connecting to some other component in the system that requires flexibility.

Installing stainless steel fuel lines and using industry-standard flare fittings are more expensive and labor-intensive, but they are absolutely the best way to eliminate leaks, reduce the number of fittings, and the connections are permanent. It does not get any better than this.

Built Tough for a Reason

The forward fuel tank is for storage, and fuel is transferred to the saddle tanks as necessary, and there is a crossover between saddle tanks, each with a “manhole”-sized inspection port.

Forward fuel tank before the deck for guest stateroom is put down.

Randy explained his philosophy when it comes to the engine room. “Assume everything is going to break in the worst of conditions.”

A great example of that philosophy, and one of particular interest to me, is that the builder does not use pickup tubes in the fuel delivery system, but rather valves and fittings located at the bottom of each tank. This ensures all fuel is available, always.

(I offer a personal experience. The owner of a sistership told me that his port engine would quit if he was in rough seas and the fuel gauge indicated less than half in his port fuel tank. A combination of insufficient or poorly located baffles in the tank and a short pickup tube caused this issue. It always stayed in my mind and I never let my fuel level go down to that level, which is not really the solution.)

When I shared this experience with these professional boat builders, Randy finished my sentence, saying that the pickup tube was too short. Wisdom from experience.

He added that fuel coming out of the bottom of the tank also make for a happy fuel pump. Pumps love to push fluid, but they are terrible at sucking fluid, such as a tall pickup tube. (That is another experience I can relate to. My vacuum gauge for the port engine registered alarming vacuum readings, far beyond spec. Eventually the engine distributor added a booster pump to the fuel delivery system, to push fuel to the engine. The engine fuel pump was working way too hard to draw fuel out of the tank and was headed for an expensive failure.)

Both saddle tanks on 5706 supply fuel to the John Deere main engine and generators. And there are switchable fuel filters readily accessible in the engine room. In fact, everything is very accessible in this engine room, and that is no accident.

Stuart said he builds boats around the engine room and access to its systems, another nod to his commercial and big boat background. Every Northern Marine yacht has full standing headroom, and no owner will ever have to kneel to change the oil in a generator.

Fittings coming off of the saddle tank on NM-5705.

“If the new owners want certain changes in the galley or accommodations, I can always make the boat bigger, but there will be no compromises in the engine room.”

That pretty much sums up the level of detail and expertise that goes into the fuel system of a Northern Marine trawler.

There is never a doubt where the builder’s priorities are.