RV generator conversion anyone?

[slowgoesit]

Has anyone converted an RV generator, or stationary power generator to boat usage?

Reason I'm asking (and we haven't even purchase our next boat yet, so I don't even know if I will need this) is I have a really nice 4 cylinder Onan 10kw 110v output generator. It came out of an ambulance bus (that's another story). Runs great, REALLY smooth, REALLY quiet compared to many 3 cylinder Onans, and absolutely SIPS fuel! Less than the 7.5kw Onan in our RV.

Seems to me that it would be relatively straight forward to:

• remove the existing radiator
• install marine heat exchanger (some thought would be needed to correctly size the exchanger)
• install a raw water pump, either electric, or running off of the existing fan pulley, or direct drive
• plumb in raw water from thru-hull or sea chest to heat exchanger, return overboard
• install a raw water strainer with shut-off
• run fuel supply and return lines, replacing all lines on the engine with marine rated fuel lines
• tie into the existing boat electrical system, replacing any wiring needed with marine approved wiring
• run wiring/mount remote operation panel to cabin

Most probably I would be replacing an existing generator, so much of the plumbing, wiring, thru-hulls for supply/overboard, etc may already be in place. I like the idea of the raw water pump running off of the engine, either direct drive, or belt driven from a pulley, although an electric has the advantage of being able to install a timer, or a temperature switch that will keep the pump running for either a preset time or until the temperature in the heat exchanger goes below a preset value.

Any comments/input?
Let the Flaming begin!

 

[Airstream345]

Seems to me is would be possible, but I have to ask...why replace an existing genny with one you would need to retrofit? Just keep the genny that comes with the next boat and sell the RV Onan for more boat bucks!

 

[Xsbank]

Too many unknowns. I would sell it or use it as backup at my house for the next pandemic.

 

[foggysail]

Too many unknowns. I would sell it or use it as backup at my house for the next pandemic.

Agree! Also notice above that cooling the exhaust was overlooked

 

[slowgoesit]

Quote:
Originally Posted by Xsbank
Too many unknowns. I would sell it or use it as backup at my house for the next pandemic.

Agree! Also notice above that cooling the exhaust was overlooked



Yup, I DID overlook the exhaust cooling! Thanks for that. On using it as a generator for the house, already have one of those, don't need two!

I'm not planning on automatically removing a working genny, just exploring possibilities. Need to see what boat we end up buying first. Thanks for the input.

 

[tiltrider1]

The cooling water is usually directed to the exhaust to cool it. If you used an electric raw water pump you run the risk of back flooding the genny when the genny stops. This issue can be avoided but it would require mounting the genny above the water line.

 

[mvweebles]

Many a good diesel engine have been ruined by improper marinzation. Apparently, it's not as simple as it looks. You will need a water pump, a way to cool the exhaust mainfold, a heat exchanger, and an exhaust elbow. And they will need to be sized properly, and mounted to the engine. Installation requires the coolant water to be redirected to the heat exchanger. When Northern Lights says they use a Kubota base engine, my guess is they order enough that it has certain modifications - threaded bolt holes in specified places to mount a heat exchanger, for example. It's not just any old Kubota engine.

In short, is it possible? Yes. Is it practical? Doubtful. Is it cost effective? Probably not (exhaust mainfolds are expensive - $1500 for a small engine assuming it's available). Will it perform well? at best, maybe.

That said, I've never done it, so would love to be proven wrong.

Good luck

Peter

 

[Arc]

Water pump, heat exchanger, shower head. Possibly not ignition protected so not good to use in bilge { check insurance co.}. I would never be able to sleep on it but I have seen some crazy stuff without explosions

 

[kchace]

Quote:
Originally Posted by Xsbank
Too many unknowns. I would sell it or use it as backup at my house for the next pandemic.

Agree! Also notice above that cooling the exhaust was overlooked



Yup, I DID overlook the exhaust cooling! Thanks for that. On using it as a generator for the house, already have one of those, don't need two!

I'm not planning on automatically removing a working genny, just exploring possibilities. Need to see what boat we end up buying first. Thanks for the input.

How the exhaust is done is QUITE important and you cannot just "use" the RV exhaust system. Unless you went with a "dry stack" exhaust (which would be quite weird for a generator in a pleasure boat and you'd need to find/create a major sized "chase" for it) you would have to convert the exhaust to "wet". This is not impossible, but could get expensive and if not done right can destroy the engine.

Ken

 

[Pete Meisinger]

Assuming that the replacement genny is diesel or gas if your mains are gas. Don't try to mix the two.

Do you have any idea how much a four cylinder diesel engine and genny weigh? A LOT!!

Getting the old one out will be hard enough, easier because you can remove certain parts. Getting the new one in will be nearly impossible. R.V. gennies are not an uncommon thing to find on the used market, mostly because they are easy to get out with a forklift.

Sell the used one and use the money to rebuild the genny in the boat if it needs it.

Something just doesn't ring totally true about that replacement genny. A four cyl. diesel should crank out a lot more than 10 Kw. And although the ambulance probably didn't need 220, and your boat might not either, the genny should produce 220 and 110.

Sell it.

pete

 

[Alaskan Sea-Duction]

I thought RV gennys were air cooled. Mine was.....

 

[StarChaser]

I priced out a set of SS risers for my 6.7KV Westerbeke @ $1500 & $2500 for the SS Exhaust manifold. My Internationals run $5000 per side.


Slowgoesit,

I'm a Master Electrician/Cabinetmaker/Journeyman Welder. It's easier/more cost effective for me to farm it out. TIG welding is HARD. Stainless lasts 20-30 years, mild steel 10yrs?

 

[Solly]

Gas or diesel ?? Depends how handy you are and how well you handle frustration. Not insurmountable. Thru hull for raw water intake, RW pump. Heat exchanger you can find, size isn't real important thermostat will keep the engine hot. You don't 'have' to cool the exhaust manifold but it will add to the heat inside the boat. Exhaust would need a Y into the exhaust hose for the RW from the exchanger and into a small water lift muffler. And a bronze thru hull sized to match the exhaust hose out the side of the boat. Then there is soundproofing...
Or just sell it and buy a Honda and run it on the swim platform.....

 

[READY]

Just speculating but this could create a problem on survey/insurance. Insurance on older boats is increasingly more difficult to get so I would not want to take that risk.

 

[slowgoesit]

I thought RV gennys were air cooled. Mine was.....

Our Dutch Star, diesel Class A has a 7.5kw Onan generator, three cylinder, radiator cooled. Most of the diesel RV generators are water cooled. Some of the older gasoline generators were air cooled.

On some of the other questions, the 4 cylinder generator I'm speaking of weighs around 450 lbs.

I'm not set on replacing a generator, as we've not yet settled on the boat we're going to buy, so I don't even know if a generator will need replacing/rebuilding. Just idle thoughts during this Covid 19 shelter in place time. Lots of deferred projects getting done around house/farm/shop.

I'm not afraid of welding up an exhaust "Y" in SS if needed. My first boat, a 1959 Monk had the cast iron 45 degree elbow just aft of the exhaust manifold fail from the inside due to exhaust gases making the corner. It also contained the cooling/muffling raw water injection fitting. We replaced it with titanium tubing, yes, titanium! Found it a Boeing Surplus in Seattle while looking for SS or Monel. 22' long, 4" OD pipe, .073 wall thickness. The specialty welding rod cost more than the pipe did! Also some smaller 3/4" titanium pipe and some flat plate to fab the water injection fittings and dispersion design inside the exhaust. Biggest problem was backing up the weld on the inside with the correct inert gas (I think Argon, but that was a long time ago) in order to prevent O2 embrittlement. The exhaust was louder than before, no cast iron mass to help absorb the sound, so back to Boeing Surplus, found 1" thick pipe soundproofing/heat shield for 4" pipe, with lead impregnated vinyl outer coating, just peel the cover off the overlapping adhesive strip and install! Worked great. Didn't hurt that I had access to machine shop and mig/tig/etc. We did a lot of Monel and SS aircraft exhaust systems, repair, and repair pretty much by replacement, as we couldn't legally build "new" aircrfaft exhaust systems due to FAA PMA (Parts Manufacturing Authority) requirements. We'd always left at least SOMETHING of the old exhaust system there . . .

The whole Titanium exhaust system was more of a "because we can" project, bragging rights, etc, than really necessary, but it was PHUN!

 

[rslifkin]

With a water cooled engine, it certainly can be done with some work. It's all about whether it makes sense in a given situation or not.

 

[WayneDana2]

I would just deck mount it in a nice sound case. Saves all the conversion issues.

 

[kchace]

I would just deck mount it in a nice sound case. Saves all the conversion issues.

 

[Airstream345]

I'm always impressed with Mads' [mad] DIY skills and his ambition to build everything himself.

 

[roddy]

No reason not to attempt conversion as long as its cost effective.
First, get genset load and safety tested for couple hours by generator shop of your choice. its $400 dollars wisely spent! Any shortcomings will be revealed.
Onan probably made same genset in marine version.
Primarily search by Kw & engine model as there are many generator voltages and 1 or 3 phase units.
Probably new used marine parts available.
Make sure the neutral is connected to chassis negative ground inside AC generator end.
When on shore power its the opposite is true, AC neutral is independent of boat negative ground.
AC Transfer switch makes or breaks this connection.
Check your local electrical code and ABYC as both have shared jurisdiction depending circumstances.

 

[Mrwesson]

Go for it. If it's not ignition protected then deck mount it with an enclosure, build one or have one built.

If it's ignition protected I dont see anything getting in the way unless your mixing gas/diesel which is just a pain.

People like to pretend their diesel engines are special when compared to auto, tractor, or truck engines but other than cooling they're basically the same. There used to be a company around that would marinize cummins diesels from trucks (5.9) for around 4k.

 

[AdkChris]

Anybody ever go the other direction? Use a marine genset for dirtside backup or off grid power? Seems there must be a lot of well made low hour gensets around that have been swapped out of boats not because they were dead but in the name of upgrading?

 

[rslifkin]

Anybody ever go the other direction? Use a marine genset for dirtside backup or off grid power? Seems there must be a lot of well made low hour gensets around that have been swapped out of boats not because they were dead but in the name of upgrading?

I've strongly considered it. Ditch the seawater pump, replace the heat exchanger with a radiator and fan and you're good to go.

 

[READY]

ADKChris- i am sure a few might do this but in my experience with looking for and buying preowned boats it seems owners squeeze any possibility of life out before they finally concede and install a new genset. In many cases the genset is the most antiquated item on the boat and even if failed they just decide they can live without. Seems boats either have low hour genset that were recently replaced or POS units that are 10 years past being reliable. My theory is due to the high cost rarely does anyone rip and replace a good genset in the name of upgrading.

 

[AdkChris]

ADKChris- i am sure a few might do this but in my experience with looking for and buying preowned boats it seems owners squeeze any possibility of life out before they finally concede and install a new genset.

Different take than mine and I know I am a newbie to trawlers. Maybe the people who replace gensets because: too small, too noisy, too big, too old, too much $ to replace hoses, don't trust, on and on are overly vocal on the internet or we have different ideas of what is still very serviceable. I agree there is also a major difference between good enough for an ocean crossing and good enough for an off grid cabin. Also you are describing the gensets still in boats listed for sale and I am thinking of all the gensets that I hear about being replaced.

 

[StarChaser]

READY,
I don't know about squeezing the life out of a genset before replacing it. I'm looking long and hard at dumping my low hr (<500) Westerbeke 6.7Kw for something else because it will not run unless I'm underway!?! The boat manual even says so, which makes it pretty useless IMO.
I have a military surplus 30kw that I think i can shoehorn into the compartment (if I use enough butter lol). I'll need to fabricate a cooling system to fit and work, but I can TiG.

Star

 

[caltexflanc]

READY,
I don't know about squeezing the life out of a genset before replacing it. I'm looking long and hard at dumping my low hr (<500) Westerbeke 6.7Kw for something else because it will not run unless I'm underway!?! The boat manual even says so, which makes it pretty useless IMO.
I have a military surplus 30kw that I think i can shoehorn into the compartment (if I use enough butter lol). I'll need to fabricate a cooling system to fit and work, but I can TiG.

Star

Now that's a new one on me. Learn something new everyday. Is it relying on a scoop intake to get cooling water sans raw water pump? Is it an exhaust issue (especially if gasoline)? Have you talked with Westerbeke about this? It just doesn't make any sense. Hopefully someone here has dealt with this before.

 

[READY]

What is the reason it can only run underway? Assuming it has access to cooling water and exhaust is not into a confined space this seems very strange? What exactly does the manual say?

 

[StarChaser]

READY,

I honestly have no idea why it works that way, but it does. The gen will start and run for about 10 minutes then shut down. I can restart, and it'll run for another 10 minutes then shut down again. The Gen has its own 2in through hull, with seacock, strainer, etc and the wet exhaust goes out just above the waterline with no restrictions. It gets clean diesel from either tank (switchable) through its own Racor. The manual says to get underway as soon as possible after starting the genset or it will shut down after about 10 minutes. No explanation why. Carver couldn't remember why but that the '82 3607 with the 6.7kw Westerbeke all had the same issue and this was their work around. The '83 and forward didn't have the same issue even with the same genset. The gen runs like a champ once I'm underway, It's not very useful if I'm anchoring out. Hence my plan to repurpose my 30kw House genset. I also plan to repurpose my solar panels from the house to Star as well. My house will become a rental property and I'm not going to leave either behind for the tenant to steal, or foul up. Their can get their own Genset and use the existing hookup. (240Vac <400amp). ETA 4 years then I'm RETIRED and doing the Loop!!!

 

[Comodave]

Well, you see something new ever day. Why would they even sell a boat with a genset that could only be run underway. We run ours sometimes when we are underway but mostly when we are anchored. It would be interesting to learn what makes it this way.