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Gas to diesel generator conversion

Old 05-16-2019, 03:14 PM
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Default Gas to diesel generator conversion

My boat is a 2014 Boston Whaler 315 Conquest.

Iím pulling out a POS Kohler 5ekd and want to replace it with a Phasor 4.5 Ignition Protected diesel.

Looking for watch-outs and things to consider.

The phaser has a smaller footprint and the new tank (about 15 gal) will fit right next to it in the bilge. Itís the identical weight of the old unit before I put the tank in, which should be less than 150 lbs full.

I know I need a fill point and a tank vent.

Iím planning to move the generator off the centerline of the boat to make room for the tank on the port side.

Iíve load tested the boat and confirmed that the 4.5kw is adequate.

What am I overlooking?

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Old 05-16-2019, 03:19 PM
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Water intrusion and ventilation are 2 big factors. If your Gen sits low then a electric water shut off valve might be needed. If you have high speed water pickups they can force water through the gen while it’s off . Then back into the motor. My Fountain Gen was destroyed that way.
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Old 05-16-2019, 03:19 PM
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Forget all the plumbing for a fill. Just fill it right into the tank through the hatch if it’s accessible
​​​​​​....
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Old 05-16-2019, 03:25 PM
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Good point, Iíll bring the tank out far enough to put a fill on the top. Is that legal/up to standards?
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Old 05-16-2019, 03:43 PM
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Certainly there is not a fire/explosion concern with a fill inboard (at the hatch). Even if it may be ďlegalĒ (I donít know) , you might want to consider the lingering smell. The interior of your boat may well smell like diesel fuel for days each time you fill the tank and that may not sit well with your family.
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Old 05-16-2019, 03:52 PM
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Vinegar helps with diesel fume smells. Diesel generally is much safer than gas, unless you go and spray it over a hot engine. But even transmission oil will catch fire if you do that.

The thing that kills most gennies (doesel or gas) is water. If it's under a hatch, make sure it's water tight. You don't want water dripping over the gennie. After that, make sure you run it every time you go out.

A water strainer in line with the cooling water line is a plus, but make sure you check it.

My 3kw diesel gennie burns about a pint an hour. It will take quite a while to burn 15 gallons unless you run it continuously. Make sure you treat the diesel with anti-microbe juice, and carry spare filters.

Make sure you have spare belts and impellers.

Other than that, they are pretty trouble free. Keep them dry, run them often, and maintain them. Mine is pushing 3k hours with no real issues. It's a one cylinder wonder.
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Old 05-16-2019, 05:00 PM
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Originally Posted by gerg View Post

Other than that, they are pretty trouble free. Keep them dry, run them often, and maintain them. Mine is pushing 3k hours with no real issues. It's a one cylinder wonder.
What genny, is yours Kubota based? I'm in the planning phase of changing our gas Kohler 5Kw to a diesel and I'm leaning towards a Next Gen 3.5Kw with the one cylinder Kubota Diesel.

I'm going to plump an external fill and vent eventually but phase one is just to get it installed. As mentioned these don't burn much fuel so filling form the bilge isn't a huge deal as long as it (mostly) goes in the tank. But I have to move stuff (cooler + seat) to get in the bilge so I dont want that to be the permanent solution. OP how easy is your bilge to get to?
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Old 05-16-2019, 05:39 PM
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It is Kubota based but is a 2 cylinder phasor. It puts out a bit more power than the next gen and it turns at 1800 Rpm instead of 3600. (Next gen is 2800 pulleyed up to 3600). I have heard good things about next gen, too. Iím not planning to put a sound enclosure in so it will fit right in where the Kohler was. Itís narrower by about 10Ē which will provide the space for the tank.
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Old 05-16-2019, 05:43 PM
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Does anyone run 2 AC units with the next gen 3.5kw?
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Old 05-16-2019, 05:48 PM
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Originally Posted by jarnau View Post
Does anyone run 2 AC units with the next gen 3.5kw?
I think it would depend on the size of the ac units. I have Mase 4.0kw which is likely closer to 3.5kw... but I only have one 14kbtu ac. It doesn't even "rev" when it kicks on. The only thing that makes it rev up is the water heater, and we don't use it.
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Old 05-16-2019, 07:03 PM
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I don’t have 2 ac’s but I run a 16kac + water heater and fridge with no problem 3.5 Next - gen
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Old 05-16-2019, 08:38 PM
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Originally Posted by jarnau View Post
Does anyone run 2 AC units with the next gen 3.5kw?
depends on the ac units...

calculate their power requirements

and power requirements of anything else you will want to run

you can get starting capacitors or whatever for most marine HVACs

you should program the units to start on a delay from one another. i have four large units in my boat. i give the first unit a minute after power is switched on (in case i quickly turn off, bad connection, other items powering up), and each subsequent unit a minute. i might lower to 30 seconds.

Last edited by mystery; 05-17-2019 at 07:56 AM.
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Old 05-16-2019, 09:01 PM
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Good choice to go diesel. I have the same generator Koehler 5EKD and it was just about to be used as an anchor after 1 year onboard. They suck, they are noisy, and require constant maintenance. However, I relocated the fuse box as well as the control board and it now works flawlessly. That being said, my next generator will be a diesel as well. Koehler just sux.
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Old 05-17-2019, 04:54 AM
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No input other than I have a Koehler 5EKD and its a royal POS.
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Old 05-17-2019, 05:04 AM
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You may want to consider some soundproofing. Diesels make a lot more noise than a gas gen. You will need a second fitting in the tank for a return line. Don't know about your current set up but switching from gas to diesel is pretty straight forward. I'll second the part about keeping it away from leaking hatches. It kills more generators than you can imagine. I would stay away from the high rpm models unless you're deaf already.
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Old 05-17-2019, 07:33 AM
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I would not select any on board diesel generator without a sound enclosure. Remember, it's not just the decibels at the exhaust but also at the head, block, intake, etc. What do the noise specs tell you? Anyone operating one without an enclosure care to jump in?
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Old 05-17-2019, 07:36 AM
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Look into a Watts fuel cell
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Old 05-17-2019, 07:53 AM
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I have the next gen 3 +/- kw suitcase gennie. I have the sound enclosure and it's still loud. But I have an inboard diesel so it's quiet relative to that. But you can hear it at night. I run it whenever the boat is away from the dock,. On canyon trips it sometimes gets pushed a little hard, but the most that ever happens is a branch circuit breaker pops. That's usually when the microwave and a couple of heaters are running. I don't have a/c.
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Old 05-17-2019, 08:03 AM
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Originally Posted by jarnau View Post
Does anyone run 2 AC units with the next gen 3.5kw?
This is going to depend not only on size but age also. I had an old 12k dometic unit which would not start from my portable generator without a soft start unit added (yes I know but this is tiding us over while I save the $$$ for the Next Gen unit as I don't want to dump money into the Kohler). It died and I replaced it with a newer version of the same exact Dometic unit and found the little Yamaha unit had no issues starting it so I sold the soft start unit. I was impressed with the reduction in starting current.

I would guess that the 3.5 would not start one of the old ones with a second one already running, but it would with the newer models. The page for that unit says:

Many small gen-sets can't run air conditioners and motors due to their low horsepower and marginally-sized generators. This gen-set uses a heavy duty 5.0KVA generator end, allowing easy starts on up to 16,000 BTU air conditioners or pairs of smaller AC units.
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Old 05-17-2019, 12:08 PM
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mine has no sound enclosure and while you can certainly hear it its not bad. sleeping on the hook with it on however isnt the nicest thing in the world but if you need it then the relief from the heat/ac makes the sound tolerable.
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