Best water heating option on cat with outboard?

[riki]

Hi folks, as title.
I have solar panels summing 300w on 3 100ah batteries and a 30hp 4 stroke outboard with alternator connected to batteries.
I am willing to put a water heating system for shower but not sure what to choose:
- 12v electric directly fed by the batteries
- tankless propane water heater


I would prefer the 12v just to avoid having to deal with pessurized tanks and fumes, but i'm not sure if my system would be enought....opinions?

[Grith]

What’s your alternator output?
I have a 240v 25 litre 800w marine hws which takes about 20 minutes to reach full temperature from cold. It was designed to be used when my yacht ( with outboard auxiliary) had shore power available but previously with a mid sized inverter I heated the water via a combination of solar, outboard alternator topped up by some of my battery capacity.
I have now just added a drop in portable 168a lithium power pack ( ecoflow delta max) which includes a high powered inverter, super fast computer controlled charging and a solar regulator all in a portable case to supplement my AGM’s which has now allowed me to sideline the previous inverter and also cook via 240v induction thus completely eliminating propane onboard as my refrigeration was already 12v compressor.
It fitted neatly in a off the shelf storage hatch with attached box which I fitted under a dinette seat with just a few vent and cable holes cut in the sides.
A bit expense but being portable it is put to other camping and home uses and leaves the existing agm battery system in place fairly unaltered.
All this is on a 28 foot trailable mono.

[riki]

Originally Posted by Grith

What’s your alternator output?
I have a 240v 25 litre 800w marine hws which takes about 20 minutes to reach full temperature from cold. It was designed to be used when my yacht ( with outboard auxiliary) had shore power available but previously with a mid sized inverter I heated the water via a combination of solar, outboard alternator topped up by some of my battery capacity.
I have now just added a drop in portable 168a lithium power pack ( ecoflow delta max) which includes a high powered inverter, super fast computer controlled charging and a solar regulator all in a portable case to supplement my AGM’s which has now allowed me to sideline the previous inverter and also cook via 240v induction thus completely eliminating propane onboard as my refrigeration was already 12v compressor.
It fitted neatly in a off the shelf storage hatch with attached box which I fitted under a dinette seat with just a few vent and cable holes cut in the sides.
A bit expense but being portable it is put to other camping and home uses and leaves the existing agm battery system in place fairly unaltered.
All this is on a 28 foot trailable mono.

thanks for your reply.
the output of my alternator is 15ah, but i have no idea if this topup could be enought to have a shower or 2 without draining my batteries.
I considered also the generator option, but i really would like to avoid having one more piece of hardware hanging around

[Rumrace]

You might consider solar heating. I’ve seen a solar bubble which you pump salt water into the bubble where it evaporates, condenses then collects warm fresh water. Certainly not hot.
Was a cool device which handled 2 jobs. The bubble inflates and floats beside your boat. Single foot pump with a valve to pump cleaned water onboard

[Grith]

Originally Posted by Rumrace

You might consider solar heating. I’ve seen a solar bubble which you pump salt water into the bubble where it evaporates, condenses then collects warm fresh water. Certainly not hot.
Was a cool device which handled 2 jobs. The bubble inflates and floats beside your boat. Single foot pump with a valve to pump cleaned water onboard

Never seen one! Have you got a link or screen shot?
I am just planning a three month no capability of resupply remote area wilderness sailing expedition and land based water sources have been known to fail very rarely.
I currently cannot justify the expense of a true desalinator for the rare once off possible use and instead have a small electric distillation unit as my emergency drinking water production backup.
I would be interested to see if that is feasible and what weight, size etc the mentioned unit is.

[thinwater]

Tanksless propane (had it on my cat--similar in size to Maldives). Just make certain it is a VENTED system with a flue. Tankless systems have about 3 times the firing rate of the galley stove with all burners on, so they can put a lot of CO2 and moisture in the air fast. No good unless the cabin is WIDE open. Also, ABYC requires vented heaters.

[JimsCAL]

Heating water takes a LOT of energy. Doesn't look to me like your DC electrical system (batteries and charging capacity) is up to the task. So either upgrade the electrical systen or go propane. Or put in a genset.

[c.K.]

Originally Posted by JimsCAL

Heating water takes a LOT of energy. Doesn't look to me like your DC electrical system (batteries and charging capacity) is up to the task. So either upgrade the electrical systen or go propane. Or put in a genset.

I fully agree with that reply, why not go with small hot water on demand that can be vented to the outside

[riki]

thanks for all your answers.

i was afraid my system would not hold as 12v water heater.
I think that my only option is to go propane: i already have a couple of tanks for the kitchen, so i'll add another one and i am done.
Actually i don't have pressurized water onboard so i'll fit a small pump to serve the heater. I guess there are heaters with built in pump, any model/brand do you suggest?
cheers

[wingssail]

Originally Posted by riki

thanks for all your answers.

i was afraid my system would not hold as 12v water heater.
I think that my only option is to go propane: i already have a couple of tanks for the kitchen, so i'll add another one and i am done.
Actually i don't have pressurized water onboard so i'll fit a small pump to serve the heater. I guess there are heaters with built in pump, any model/brand do you suggest?
cheers

It doesn't meet ABYC recommendations but you can "T" off your existing propane line to feed a water heater. Use armored hose and put a shut off valve in it. Many people are terrified about propane but I've found that any leak is immediately apparent because of the fragrance which is in propane. Make sure your bottles are in a sealed off propane locker and shut off the propane source when not in use. (these recommendations apply whether or not us use an instant water heater)

You will not find a propane heater with a built in pump but in many third world countries these products are common and inexpensive.

https://www.amazon.com/s?k=propane+w...f=nb_sb_noss_1

You can get better pumps at a marine store but I found several like this on Amazon https://www.amazon.com/s?k=propane+w...f=nb_sb_noss_1

[Cpt Mark]

[QUOTE=wingssail;3693256mediately apparent because of the fragrance which is in propane.

There s good reason to be fearful of propane obviously. Yes you can smell it if there's a alot of it but if it's a small leak going into the bilge you probably won't. If it's a HUGE leak but under a settee you will eventually but by that time, a lot of propane is where you don't want it. In a classic brain fart moment while working on my boat I had to disconnect the propane infeed line where it joined under a settee. Many hours later I forgot to reconnect it and went to cook dinner. Almost immediately the propane sniffer alarm went off and shut off the solenoid valve. This was not the sniffer below the stove, this was the 2nd one in the bilge.

I have gotten rid of all propane on my current boat. All electric, LiFePo4 batteries with solar to come. Won't have to hassle refilling propane tanks, or figuring out where to get an adaptor for whatever country I'm in and zero chance of an explosion.

If you have propane on board, you really should have a sniffer system as well. A sniffer mounted below each propane device and in the bilge. My bilge one went of every few months. Had to clean the top with a quick swipe of a rag.

[wingssail]

Originally Posted by riki

Hi folks, as title.
I have solar panels summing 300w on 3 100ah batteries and a 30hp 4 stroke outboard with alternator connected to batteries.
I am willing to put a water heating system for shower but not sure what to choose:
- 12v electric directly fed by the batteries
- tankless propane water heater


I would prefer the 12v just to avoid having to deal with pessurized tanks and fumes, but i'm not sure if my system would be enought....opinions?

Your system would not be enough for an electric water heater for a shower. It takes around 600watts to heat a gallon water 10 degrees. That is twice as much power as your solar could put out and in a 5 minute shower you'd exhaust your batteries completely (even if they are lifepo4). Let's not even talk about a cold climate.

Propane instant, on the other hand, is practical if you have a pressure fresh water system and propane tanks. Our propane instant water heater makes our hot and cold water taps seem like a home based system.

But for a minimalist approach on a small boat, a couple of sun shower bags might do nicely.

[Grith]

For many years I just added a little stove heated hot water to an already warmed water solar shower to bring it up to temperature on my previous tiny 20 foot trailable cruising catamaran with 18hp outboard.
I know many others are very comfortable with propane on board but I am not personally having seen my mum lose some friends to explosions on board their boats on a couple of different occasions.
I will admit they were back in the days when many smoked and cigarettes were thought to be the ignition source.
Both also occurred when returning to moored boats which had apparently developed leaks and accumulated gas whilst sitting locked up.
At 15amps from your alternator and 300watt Solar you are a little light on for power production for electric hot water though one cold to cutoff hot heat of my 25 litre capacity 240v 800w marine hws with a fairly efficient sine wave inverter consumed just over a 1/3 of my previous total available similar 150 amp (from 300 amp AGM) battery supply.
With other normal uses this was pushing it far too close hence upgrading both my solar system to 600w and adding the 168amp lithium portable battery pack 2400w inverter system. ( I have removed one 100amp agm battery and my previous 1800w sine wave inverter of close to combined equivalent weight and now have over 250a of usable power versus my 150a previously )
My solar panels now charge the ecoflow whilst my alternator remains linked to the two remaining agms which still run the bulk of the regular yacht systems.
If required I can also charge the agms via a 240v charger hooked to the ecoflow unit.
This has also allowed me to replace using my origo alcohol stove with the much faster portable induction cooktop shown here.
The lithium power pack is remotely controlled both output switching on and off and input and usage monitoring via phone app on the screen pictured via screen shot.

[motion30]

I have a 3 galloned whale water here. It's a 110volts Of course I am in South Florida but I literally turn it on for 5 minutes to warm the water enough for a shower

[Tupaia]

Not a cheap option but you might consider a small 4-5kw hydronic heater. Eberspacher or Webasto. It would require a calorifier.