The Big Project: Genset Installation

LUX is an ex-charter boat, with a four cabin layout popular in the BVIs. As such, she came without several things that make life much better along the US east coast, such as a powerful inverter, air conditioning, and a genset. 

We caution that a genset install is a lot of work and requires experience with 12v and 120v electrical systems, engine cooling water supply, fuel systems, and exhaust. It isn’t an installation to be taken lightly. This project has been our biggest so far because it touches almost every system on board. Planning and preparation took a long time and installation was done in phases.

The Most Critical Step: Planning

We decided to use a small genset along with a Victron MultiPlus 3K inverter that provides power boost to allow starting large loads such as air conditioner compressors. This allowed us to use a 3.5KW genset instead of the normal 5KW-6KW unit that most L40s contain. The advantage is that the genset runs at a higher continuous load, which is better for the diesel engine. Note that some owners create larger engine loads by turning on multiple loads like hot water heaters, water makers, battery chargers, and air conditioners. See our prior posts about the Victron Multiplus installation and its setup.

We investigated a variety of gensets, looking for reliability, ease of maintenance, readily available parts, light weight, and capacity of 3-4KW. The Northern Lights gensets fits all these characteristics except capacity. Their smallest is the M673LD3 at 5KW (60Hz) and 377 lb. We found the NextGen 3.5KW at 160 lb, which would be about 200 lb by the time we added muffler, exhaust, and sound enclosure. It uses a common Kubota engine and the 5KW generator head that's on the NextGen 5.5KW.

Laying out the pieces

Then we planned how the different systems would work (fuel, exhaust, 12V, 120V, cooling water). The most logical installation location was the port forward locker, keeping the existing water tank. There is sufficient space to service the engine. We hope we don't have to service the water tank - it may not come out in one piece. We would likely replace it with one or two 50 gal tanks if we had to make a change. If a watermaker is ever installed, replacing the water tank with a 50 gal tank and using the remaining bulkhead space for the water maker seems like the right approach.

We researched installing the exhaust between the hulls and couldn’t come up with a definitive answer that said that it was ok. We found a brief reference to running exhausts as far aft as practical. We found that most factory installations used a water separator in the forward locker to separate the water from the exhaust. But that requires another hole in the hull to exhaust the water, typically under the water line to minimize noise. All factory installs we examined had the exhaust run all the way aft, regardless of whether a water separator was used. Since the exhaust hose can be run with a gradual slope all the way aft on the L40, we stuck with the simple water-cooled exhaust design. NextGen says that this small engine can work with the required length of exhaust hose. No anti-siphon is needed in the exhaust line since the genset is always significantly above the water line.

For more thoughts on genset installations, check out a great article in Professional Boatbuilder by Steve D’Antonio: Generators Done Right.

Installation

Mounting

Locker floor leveled and measuring installation

We decided to encapsulate a piece of 3/4 inch plywood with epoxy and through-bolt it to the floor of the locker. The locker floor isn’t exactly flat, so we added epoxy with micro balloons to level it.

The sound enclosure is mounted on engine mounts to the plywood. The genset itself is also mounted on engine mounts inside the enclosure, making the system double isolated, reducing vibration induced noise. The double mount also raises the engine enough to safely feed the muffler without risking water backing into the engine cylinders and causing hydro-lock.

The sound enclosure engine mounts are through-bolted through the plywood and the floor of the locker. Finishing nuts were used on the exterior. Two of the bolts went through where the hull takes a turn, so we constructed two custom fitted fiberglass extensions that we coated with gelcoat so they would match the hull.

Through-bolts with finishing nuts

Fuel, Exhaust, and Cooling Water

Exhaust fitting

The fuel supply was with a Tee connection off the main engine filter, using a small 12v diesel fuel pump to push the fuel to the engine. We tried without the pump and it wouldn’t run reliably. The return is a Tee connection into the engine return to the fuel tank. 

The engine connection to the muffler uses two 90-degree silicon adapters to make the S-curve that was needed. The muffler was installed next to the genset. 

The exhaust hose runs all the way from the muffler to the stern, with no breaks or couplings to cause problems. Running the hose was a challenge because there was a small triangular opening at the bulkhead into the engine compartment. This opening could not be reached from inside or outside. So we used a GoPro camera with WiFi to an iPad to see the hose and guide it into the opening. It just fit! We wanted an exhaust fitting that matched the Leopard engine exhaust fitting. We finally found one from Buck Algonquin.  

Thru-hull, filter, manifold, raw water pump

The fuel hoses fit into the remaining spaces around the exhaust hose at the engine compartment.  The fuel filter and heat exchanger cooling water overflow bottle are mounted on the bulkhead in the fwd locker. 

The engine is about four feet above the water line and the little Johnson water pump wouldn’t pick up water that far. So we installed a low head 120v cooling water pump in the port hull bilge to supply water to the water pump. Power to this pump is provided by a tap off the genset 120V AC output. It first goes to a fuse, then to a GFCI outlet that powers this pump whenever the genset runs.

For cooling water, we increased the size of the thru-hull in the port hull, connected to a Forespar Marelon filter, to a Groco manifold that feeds the port head, the port air conditioner pump, and the genset water pump. This arrangement allows us to use one through-hull for all raw water supplies on the port side. We took this opportunity to upgrade the seacock and provide a stronger mount.

Cooling Fan and Wiring

The enclosure cooling fan was installed right on the cabinet and vents out via a clamshell vent mounted in the oval space in the windlass locker. Its power comes from the 12v control connector block on top of the generator head. It is the black hose running up from the back left (inboard end) of the genset in the Installation Complete photo.

Installation complete

Genset control in upper right

Starting power was taken from the windlass cables since we don't anticipate running the windlass and starting the genset at the same time. There is already a 100A circuit breaker in this circuit. This eliminated a battery and its associated weight, charging, and maintenance. The 120V AC wires are routed to a relay that automatically switches the boat input from shore power to genset whenever 

the genset runs.

The control panel is mounted above the 120V Shore Power panel. Power to the 12V diesel fuel pump is supplied from this panel instead of running a wire from the genset all the way aft.

Storage shelf

The Shelf and Service Access

Since the genset consumes a large amount of our forward storage locker, we 

built a shelf that mounts above it. The shelf is good for 

relatively light things like the spinnaker. There is space forward of the muffler and genset to hold a folding bicycle, two plastic storage tubs (that's where we have the extra snorkel gear) and the grill.

The shelf unscrews and is easily removable to allow access to the engine. 

With the shelf removed, the sound enclosure can be easily removed from both sides of the engine to allow for full servicing.

Open for service

Our Experience

It took some experimentation to refine the installation. We initially tried running without the fuel and raw water lift pumps and found that they were needed. It is surprisingly quiet. It is so quiet that we can't hear it start if the main engines are running. It isn't obtrusive even at anchor. The little splash of raw cooling water lets us know that it is getting properly cooled.

We use the genset to quickly recharge the batteries after a couple of days of not motoring. We don't (yet) have solar and the genset can quickly put 100AH back into the LiFePO4 battery bank.

We have used this system in hot and cold weather to make our travels more comfortable. In the hot, humid Chesapeake summer, we often use it to cool the boat in the evening before going to sleep. Simply reducing the temperature a few degrees and removing a lot of the humidity makes it much more comfortable. Our cool spring and fall trips on the ICW give us an opportunity to use it to warm up the cabin.