Second Chance Gemini 3400
The size of the generators available makes adding a full genset to the boat
a challenge. I chose the NextGen 3.5kw water cooled, diesel generator as
the best available choice. The genset weighs about 160 pounds so it doesnt effect
the weight greatly. The genset only consumes about .2 gallons per hour
and I use a 5.5 gallon tank extremely well marked for diesel only. The generator
is mounted in the starboard aft locker with wiring run into the cabin. It is controlled
from inside the cabin with the remote start/stop panel and shore/generator switch
Steps for Installation:
Prepare the locker for installation
clean everything out and make sure it is completely sealed at the bottom
Have everything ready for the installation.
Purchase everything in advance so you don't have those last minute trips to the store
You need the generator itself, a thru hull fitting and hose, muffler, hose, thru hull exhaust
fitting with flapper, the extra wire for the remote start panel, wire for the AC back to the panel
a vent grill, 2 150+ cfm fans, low profile dorade, automatic bilge pump, hose and thru hull, a piece
of starboard lumber, 10" shelf supports, lots of clamps and lots of different screws and nuts AND
always several tubes of 5200
Take the boat out of the water
This is a great chance to do every project you wanted to get done when the boat is out of the water
I took the opportunity to fix a couple of nicks on the sides ( too close to the dock)
Touch up the bottom paint, add flappers to the cockpit drains, etc.
Add the thru hull. I installed a new brass thru hull in the starboard hull in the most forward access hole
and routed the new hose under the floor, using an inline filter mounted under the floor at the aft
access hole, through the aft starboard cabin, under the berth and into the sealed area under the
mattress. Be careful to maintain the integrity of the sealed chamber by using 5200 on every hole
you make. Drill a hole in the bottom of the aft starboard locker and route the hose up and into the
locker. Seal this hole extremly well. Use oversize ( from mfr's reccomendations ) hose from the
thru hull to the genset. The pump on the generator doesn't like the long distance but using the slightly
larger size hose, there was no problem. I used rigid plastic hose from the thru hull to the generator to avoid
any accidental bends or crimps. There is also a backup AC pump powered by the generator installed on this
line in the event the generator pump fails. It is a free flow pump so it doesn't restirct the water flow when
it isn't on. The wiring for this was routed back to the Shore/Generator switch on the generator side.
The exhaust and bilge thru hulls are next. I installed both to vent between the hulls with the exhaust
just below the bilge. The exhaust thru hull is 15" above the resting waterline.
The wet muffler is installed on the bottom of the locker, near the center- aft. This allows the exhaust hoses to be
curved gently so that NO 90 degree bends are required. I used the Centek 1.5" top in, side out wet muffler
and screwed it to the bottom with a touch of 5200 under the screws. I mounted the bilge pump and automatic
switch in the center of the locker. The hoses were installed and double clamped where possible. The main exhaust
hose was routed up and left sticking out of the locker at this time as were the wires for the bilge pump.
I installed a 150 cfm fan on the starboard side of the locker beneath the shelf and ran the input hose up to a
low profile dorade installed in the deck. The flow is to bring air to the lower part of the locker. A 5" x 10" hole
was cut in the top rear step into the locker with a grill on each side. The grills were placed upside down of
each other to minimize any splashing into the locker. I also took advantage of this time to install a plastic sheet
under the rudder lines to keep water from entering the locker. I used a thick plastic carpet runner, trimmed to
about 12" and placed it under the lines and routed it down to the drain area. I secured it with small screws.
I lined the entire locker with soundproofing / heat shield material. This is similar to the stuff used under car
hoods and I purchased it at Auto Zone for about $15. I used the 3M spray on glue to put it on. I installed the
shield on all sides including the lid of the locker.
Once you are sure there is nothing else that you need to get into the bottom of the locker for, you can install the
shelf brackets. I used three brackets, one on each end and one on the center. I installed a 12" x 27" piece of
starboard lumber, level with the existing "shelf" for the generator to sit on. The starboard was secured to the
brackets with thru screws and nuts.
The wiring for the fuel lines, battery, AC, and remote panel need to be put in next. Diesel engines require
two fuel lines, one for supply and one for return. These were routed into the starboard cockpit locker where
the fuel tank and filters would be placed. I routed the 12V for the battery from the engine battery through
the other cockpit lockers. The engine battery and cut off switch were previously re-located to the port cockpit
locker so the generator was connected in parallel with the outboard on the isolator switch. The AC and remote
panel cable were routed with the outboard control and propane lines which were already in the starboard cockpit
locker. Run all the wires and lines at the same time with the use of a electricians fish tape. This is not something
you want to have to do twice. Once all the wires are in place, reseal with 5200 in the locker. I drilled a hole from
the cockpit locker into the aft locker and ran all the wires through the same hole and resealed. All the wires come
out in the starboard berth. The AC was routed behind the fridge and into the electrical panel. The remote panel wires
were routed behind the fridge and up the shelves to where the existing AC outlet was.
Connection of these is discussed later
With all the wiring, muffler, water hoses, etc installed, the boat was ready to have the generator put in place.
I suggest having a few strong friends around to make this part easier. I managed it with just one friend and it
was a struggle but we didn't kill each other or cause any additional damage to the boat or generator. We lifted
it from the ground with the help of the main sheet onto the deck next to the locker. The air intake, water pump
cover and screw were removed and final measurements were taken. All indications were that it would fit. Close
but it would fit. We moved it into place and the water pump pully was about 1/4" inch over the width of the
locker. I hastily grabbed the rotozip and trimmed about a 3/8" cutout for the pully. With this done, the genset
slid/fell into place.
The air intake, water pump cover and mounting screw were reinstalled. The fuel lines, water input, battery cables,
were hooked up. The AC and control wiring was hooked up. The bilge pump was connected directly to the battery
and the fan was connected to the 12v relay that switches when the unit is on. The exhaust hose was gently curved,
cut, and connected. The generator itself was bolted down with large thru bolts, two into the starboard aft cabin and
two into the starboard lumber. This takes some agility and hopefully someone with small arms to reach into the locker
and put the bolts in. Once it appears that everything is connected, installed and ready to go, RECHECK everything.
I mounted the coolant reservior on the port side of the locker. I mounted an additional 140 cfm fan in the aft port corner
to circulate air around the top of the generator and wired it to the 12v relay so it would only run when the generator was on.
I routed all the wires around the aft side of the generator and secured them with tie wraps to the screws on the grill.
I installed the remote panel next to the existing AC outlet in the main cabin right by the door. The hook up was simple
as it comes with a premade molex plug on the end. I mounted a shore/generator switch inside the electrical area, facing
forward. I connected the main incoming shore power leads to a shore/gen switch as I did the generator supply wires.
I noticed quite a bit of original wiring that had gotten hot over the years and some loose wiring, this was all replaced
with oversize wire and tightened.
NOTE: Even if you are not considering installing a generator in your Gemini, I suggest you check the original wiring
for signs of overloading and the tightness of the connections. A loose neutral could cause an electrical fire.
I used a standard gasoline fuel tank for the diesel fuel and marked it extensively for DIESEL only. I added a return
port on the top of the tank for the diesel fuel. I would have preferred to use a proper diesel tank but to this day, I have
not found a proper portable diesel fuel tank. While I do get some strange looks when I fill up all the tanks, I have
never had a problem with it. I mounted a fine filter / water seperator device beside the tank and every other tank, I
put diesel fuel conditioner in the fuel.
Once all the connections were made and rechecked, I put a water hose into the thru hull fitting and cranked it up.
It started on the first try and after a few spurts and sputters getting the air out of the fuel line, it came up to speed
and ran perfectly. The water output from the wet exhaust was adequate and no leaks in the locker. Now came
time for the electrical test. I switched the shore/gen switch to generator, with the main AC breaker off and nothing
blew up or smoked so I figured that much was ok. With all the individual breakers off, I turned the main AC on and
then each individual breaker until they were all on, including the air conditioner. My AC amp meter showed me drawing
13 amps with everything on the boat running. 13 amps AC at 120 V translates to about 1600 watts which is full load
of the boat, so you might ask why I purchased and installed a 3500 watt generator. It takes almost 2800 watts to
start the AC and while this is a momentary requirement, smaller generators would not be able to supply the power
to start it and keep it going. I would have purchased a 3000 watt generator but did not find one available that
fit the size requirements. This generator was perfect for this application. It is not terribly heavy, extremely user
friendly, reliable and most of all QUIET.
With this monumental task out of the way and the boat out of the water, I finished the rest of the projects that I felt
needed to be done while it was out of the water. The entire project from out of the water to back in was 3 long hard days.
Practical application: With the boat back in the water using the outboard cruising at 5 knots, running the generator
wasn't a problem. Any faster and the exhaust thru hull tends to get buried in the wake. The same is true for operation
under sail. Anything above about 5 knots and while everything works, I feel that the water line at the exhaust output
isn't a good thing.