Just as an additional point - it's only 4L/hour because I made a mistake with my rpm
and pulley ratios - I calculated based on 2800 rpm
, as I was getting too excited and started with by looking at the efficiency curve instead of required power... so I chose the most efficient spot for fuel consumption
and went from there - but don't need the full 27HP at that rpm... I only need about 10HP...
So going with 2200 rpm - I could have had this down to 2.3L/hour - but your math still works out better... (but the difference is not as hideous as before.
Believe me, I am really short on space (and waterline).. this is an old racing
boat with quite a narrow beam that I've totally ripped out the insides of and redone, but unfortunately the hull
is still the same size as when I started...
I was feeling romantic at the time so thought against buying
a brand new beneteau
(we'd have been "out there" for about 4 years by now with that option... *sigh*) .... but this is another story..
On the Honda
- yes I have an EU2000i and in fact bought it specifically for this reason originally, thinking of the better fuel economy etc - but there are again various limitations which I've been wracking my brain over and can't resolve.
I have 250L of diesel
tankage and 200L of water. Philosophy here was that "I can always make water, but not diesel"...
Batt bank is approx 700AH AGM
. Chosen such that running my hideous 240A alternator
combination, I can pump the bank full in about an hour. During that hour, I can also use the watermaker
(cat 247 pump) on the engine
(bought already.. oops) - to produce about 100L of water... about half the tank - meaning no limitations on water usage.
The only thing left here is hot water - still an unresolved issue. I have a raw water
cooled engine - so no heat exchanger
.. meaning that even if I take the hose off the exhaust
manifold and run it though a really efficient/long externally mounted separate heat exchanger
unit before plumbing
it back into the mixing elbow
, I'd probably only take the chill off the water since the engine will only be running at ~40degC anyway.. this part I'm not 100% sure of and will have to see when the engine is commissioned to see how hot I can actually get the water. (I have a very small
hope that it will warm the water sufficiently... but not holding my breath..) If this doesn't work - then I need another solution.
Now the theory here was that at 4L/day diesel consumption
- I'd get water, power and maybe hot water and assuming efficient usage/timing with moving around etc - it means 62 days without refuelling - away from civilisation. If I redo the pulleys - this will come down to 2.3L/day - meaning 108 days without refuel... much better.
Now on the Honda
option - at the moment, I have no petrol tankage at all. Just jerry cans. Assuming say a max of 80L worth of jerry cans stowed around the place - the Honda eu20i will drink about 1L/hour at full load. Meaning 80 hours of runtime max - and if and only if I can complete charging
etc in 1 hour per day - that means 80 days between refuels - which is not too bad. (Please note - I value days between refuels much higher than saving $)
Now comes more complexity - with the Honda - I will need a charger
... it has been explained to me that the Honda won't power much more than a 75A charger
... so this is way less than the alternators, and won't "saturate" the AGM
acceptance rate on the bank... so it's probably more like 2-3 hours to charge the batts..
But, with all the power going to the charger - there's also no power left to run a watermaker
with an AC motor
One saving grace here is that with a Honda - I can buy an intant electric
waterheater... and shower
with that... but again, not all within an hour.
So to make the honda work - I'd have to do it in series - 2-3 hours charging, 1 hour watermaking, then shower
. So we're now back to 4 hours or runtime... and 4L/day.... and with less petrol aboard than diesel - we're down to only 20 days between refuels (not counting outboard
usage.. but we'll ignore that for now).
So since I really
can't fit a diesel genset - (I really mean this - even the Honda would have to be stored in
the cockpit in a purpose made box and will barely fit) - I have limited options for making this work - either somehow massively increase petrol tankage for the Honda, or just run everything off the main engine.
I would greatly appreciate wisdom and solution to this dilemma - but no matter how I look at it, the only way I can solve/optimize the problem is using the main engine.
Of course, I remain open to education and BetterSolutions(tm).
(By the way - there will also be a solar
panel in the mix as well to help top up the batts as well.. no windgen though)
Unfortunately the Cat 247 pump just arrived.. but the other thing I just remembered is that to run the 247 at max output - you need an approx 2.5HP motor
- which the Honda can't start due to the inductive load at start... :\ So if I couple to an AC motor - I'd have to run a smaller motor and run for longer... thus again increasing fuel consumption...
The problem here is that the last remaining bit of space I could possibly manage for a diesel genset is about the footprint of a Honda eu20i. I've just googled what is available here and there's nothing much smaller than something about twice that size... The only other crazy thing I can think of is to buy a really small air-cooled portable diesel genset - remove the frame and try to wedge it in somehow.. :\