Fuel capacity vs fresh water capacity

I am considering removing one of my 2 smaller fuel tanks. It would leave 1 smaller tank and 2 larger tanks still in place. That leaves between 500 to 600 gallons of fuel capacity, or well over 1200 miles of range (probably more like 1500) with the 3 remaining tanks.

I would replace the tank with an additional fresh water tank and some useful storage. This tank is in the lazarette area (under the cockpit). The tank is not leaking.
This is a 30-year old trawler for near shore cruising, not a passage maker. I cannot imagine any future owner would need more fuel or range. I also think they would benefit from the extra fresh water and storage. Instinctively, I hesitate to reduce fuel capacity/cruising range, yet the extra water and storage are more appealing than what seems like more fuel capacity than we need on this boat.

Any thoughts?

How much water and holding tank capacity do you have? While having lots of fuel capacity allows you to shop and travel for the best fuel prices, there should be balance on how long you can go between water and pumpout stops. As a comparison, my 45' boat has 650 gallons of fuel (2,000 mile range), 300 gallons of water, and an 80 gallon waste tank.

Ted

How much water do you carry? That may make the difference. But if you have 1000+ mile range, that is probably fine. We don’t have near that range. I would like more water also but don’t have anywhere to put a tank.

AZ2Loop said:

I am considering removing one of my 2 smaller fuel tanks.not a passage maker. ...I cannot imagine any future owner would need more fuel or range. I also think they would benefit from the extra fresh water and storage.

Any thoughts?

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The answer depends a lot on your fuel consumption and your cruise radius. But I can tell you this:


I have two hungry 10 liter Cat diesels with 380 gals of fuel, with good data on consumption and sorta predictable gauges, and 180 gals of water. I have never worried about fuel, but often wonder if I have enough water.


I seldom run below 3/8 fuel, but have actually run my water low enough that an unexpected shortage in rural BC caused me to divert six hours out of my way to tank up.

AZ2Loop said:

I am considering removing one of my 2 smaller fuel tanks. It would leave 1 smaller tank and 2 larger tanks still in place. That leaves between 500 to 600 gallons of fuel capacity, or well over 1200 miles of range (probably more like 1500) with the 3 remaining tanks.

I would replace the tank with an additional fresh water tank and some useful storage. This tank is in the lazarette area (under the cockpit). The tank is not leaking.
This is a 30-year old trawler for near shore cruising, not a passage maker. I cannot imagine any future owner would need more fuel or range. I also think they would benefit from the extra fresh water and storage. Instinctively, I hesitate to reduce fuel capacity/cruising range, yet the extra water and storage are more appealing than what seems like more fuel capacity than we need on this boat.

Any thoughts?

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Your estimated range indicates a fuel economy of 2 mpg on what you will have after the conversion of 1 tank from fuel to fresh water.
By comparison, my 45' boat has about the same fuel capacity, same economy and 300 gal of fresh water. If I were to go on a 1200 mile journey, I would likely run out of water before I would run out of fuel.
Luckily, most, if not all fuel stops can fill your water as well.

koliver said:

Luckily, most, if not all fuel stops can fill your water as well.

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Shearwater comes to mind.

AlaskaProf said:

The answer depends a lot on your fuel consumption and your cruise radius. But I can tell you this:


I have two hungry 10 liter Cat diesels with 380 gals of fuel, with good data on consumption and sorta predictable gauges, and 180 gals of water. I have never worried about fuel, but often wonder if I have enough water.


I seldom run below 3/8 fuel, but have actually run my water low enough that an unexpected shortage in rural BC caused me to divert six hours out of my way to tank up.

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Sounds like you need to add a watermaker.

A sailor friend who has circumnavigated advised that a stream of water from the tap that is thicker than the lead of a pencil is wasted water. I never tested the theory.

It would be helpful if you told us how big your current tank is and how big the 'spare' tank is you are considering for conversion.

Exactly why do you want more water? Are you running out of water often? Is there not good supplies of water where you cruise? I'm not sure I would go through the headaches of that conversation unless I had a good reason to. My NT37 has a 1000 mile range too but I usually never go more than 60 miles a day and I only spend weekends on the hook. I can get water almost anywhere but i am able to pick and choose my fuel stops according to price and fuel quality.

Is a water maker a better idea?

Install a water maker and keep the fuel tanks. The only remaining problem is the holding tank size.

Advantages of the bigger boat
We have 7000 litres of fuel (1850 gallon) for 3500nm @ 7.5kn.
Have 5000 litres (1320 gallons) capacity of water
Because of that we need no water maker
And need no marina berth.

We see a fuel dock/water fill once a year
Have not been in a marina in 4 years.

Money saved is far more than cost and maintenance of bigger boat.
Only works if you actually use your boat.

I think it would be a good move to make those changes.

Great replies. Thanks for all who contributed so far. I'll try to answer what questions were asked.

Our water storage is about 160 gallons at this time. The size of the tank I would add is yet to be determined, but even 40 gallons would be a 25% improvement, and I'm sure I would add more than that.

Like most of you who have replied, I have rarely (if ever) gone below 1/2 tank on the fuel. We are basically cruising around FL and the SE coast, and may make our way up to the great lakes next summer. Fuel is easy to find, as is water, and I do like filling up when I find a good price, and I would lose a little of that ability if I do this, but not much.

When anchoring, we can go about 2 weeks pretty easily on water right now, with both of us showering daily and being conservative with water. If long term anchoring, water is our limiting factor. Candidly, by that time, we usually want a marina before that anyway. That may lead you to ask "then why go through the trouble of making this change?" or something like that.

One additional reason is that I am considering changing our master head to a fresh water flush toilet. I think that would be a nice improvement over salt water flush. Without adding water storage, I would not make that change. Water is too precious with 160 gallons of storage to go to fresh water flush. While resell is not a huge concern, I do still consider it, and I think another owner of this boat would benefit from the extra water more than they would miss the fuel.

One other benefit from doing this is weight distribution. Everything heavy seems to be on the starboard side of the boat. The dingy is offset that way, and its outboard is also on that side. Refrigerator, batteries, holding tank, etc. are all on starboard side or slightly offset to that side. The result is a very minor (when fully loaded) list to starboard. It's barely noticeable, but I still see the "lightening up" of the starboard stern quarter as an advantage in that regard as well. I realize water weighs more than fuel, but there would be less water so it would be lighter by probably 300 to 400 pounds. Being located on the far starboard stern quarter, it would probably have a positive effect.

I think that answers the questions asked and gives a little more info on why I am considering it. It will be the removal of a 30 year old steel tank if I tackle the project. I do have good access to it, though it might need to be cut up to pull it out. It will be a bit of a project, for sure, so I need to figure out if its worth it.

Thanks again for the thoughts.

You can make water with enough fuel, but you can’t make fuel with lots of water....

Fresh water is about 8 pound per gallon.

From Seattle through BC's Inside Passage to Ketchikan Alaska, the furthest fuel jump is 85 miles. I know dick all about Florida and the East Coast but I'm willing to bet the distances between fuel jumps is short.

rsn48 said:

From Seattle through BC's Inside Passage to Ketchikan Alaska, the furthest fuel jump is 85 miles. I know dick all about Florida and the East Coast but I'm willing to bet the distances between fuel jumps is short.

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I never thought about it in this way. It seems like there are much longer jumps along this route!

-tozz

Yes, access to fuel has never been a problem where we have cruised. Nor is access to water, but we do run out of water well before we run out of fuel if anchoring for an extended amount of time.

This change to hold more water (at the cost of less fuel by removing that one tank) seems like a good change to me. The reason I started the thread was to see if there would be a lot of people advising to never reduce fuel capacity. So far, I'm not seeing that in the responses and I am pleasantly surprised by that.

One thing I have noticed in the responses is that our fuel to water ratio is very heavily weighted in favor of fuel compared to most of the responses. That further suggests this change (adding water, reducing fuel) is probably a good one to make.

I appreciate all the replies!

Mike
I don't anchor for as long as you indicated but I'm with you... if you style of cruising would benefit by the change I would say go for it. I agree with your analysis of others ratios.
The clincher for me is if you anchor for long times you burn little or no fuel but do use water. Make it work for you unless you are thinking replacement in the future.
I still don't think fuel capacity remaining is a big negative.

A better water capacity has the advantage that you can TASTE the water before bringing on board.

Some dock water tastes like swimming pool drainage .

Your boat, your money.
I would lean towards keeping as is and adding a water maker.
Holding tank capacity reminds of the California saying, "If it's yellow, let it mellow. If it is brown, flush it down."

I suspect 4 people can go at least a week without filling up the holding tank.

I carry 150 gallons of fuel and 45 gallons in the holding tank and a FW VF. 4 people did not fill up the holding tank but water usage was surprising great. Showers and cooking were the highest usage.

I too am surprised the replies in this thread are as accepting to reduced fuel as they are. At the very least, trawlers seem to have an aspirational appeal (versus practical application) to venture distances self sufficiently. I would have thought a watermaker would have had more support than it does in this thread. I guess it all depends on actual vs intended usage. People just don't go too far from civilization I suppose.

If it makes a difference to OP, depending on the boat and likely buyer, resale may be adversely affected. Buying a boat is a dreamy state of cruising. Trawlers imply distance capability. Reducing that may carry a resale cost even though for all practical intents, no one will need the range. And carrying excess fuel has its own downsides.

Peter

When we bought our boat, a DeFever 44, the aft tank under the master suite bed platform had long since been decommissioned. The reason was that it had rusted out big-time. I attribute its demise to a design flaw. The aft tank on DF44s sits in a shallow vee. The tank bottom is also a shallow vee to conform to the hull there. That vee is also the path that seawater from the rudder packing glands take to the aft bilge pump well. Over the years that very high humidity environment promoted rust. It was ugly. We had it removed. When the yard cut away the top of the tank about four inches of "mud" was found in the bottom. My guess is that the "mud" was dead diesel eating critters.

In place of the tank, I installed a sheet of marine plywood, suitably prepped, across the stringers. We use that for long-term storage under the bed platform. I will soon be moving the water heater from the engine room to under the bed which is another long story. I could have installed another water tank or a holding tank for the aft head using the separate fill and vent lines for either. But, I do not miss that extra 235 gallons. We still carry 720 gallons of fuel which gives us a safe range of 1,200 miles. I think 1,200 miles serves most here quite well. As for another holding tank, that would have been nice and still could be done. The flush from the head would be only a 10-foot downhill run and I imagine I could fit more than a 100-gallon tank there. Our holding tank is 45 gallons. A big plastic water tank would be nice also, maybe 200 gallons also easily plumbed into the system. We carry 350 gallons of water.

Boats - choices, choices, choices.

mvweebles said:

I too am surprised the replies in this thread are as accepting to reduced fuel as they are. At the very least, trawlers seem to have an aspirational appeal (versus practical application) to venture distances self sufficiently. I would have thought a watermaker would have had more support than it does in this thread. I guess it all depends on actual vs intended usage. People just don't go too far from civilization I suppose.

If it makes a difference to OP, depending on the boat and likely buyer, resale may be adversely affected. Buying a boat is a dreamy state of cruising. Trawlers imply distance capability. Reducing that may carry a resale cost even though for all practical intents, no one will need the range. And carrying excess fuel has its own downsides.

Peter

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catalinajack said:

When we bought our boat, a DeFever 44, the aft tank under the master suite bed platform had long since been decommissioned. The reason was that it had rusted out big-time. I attribute its demise to a design flaw. The aft tank on DF44s sits in a shallow vee. The tank bottom is also a shallow vee to conform to the hull there. That vee is also the path that seawater from the rudder packing glands take to the aft bilge pump well. Over the years that very high humidity environment promoted rust. It was ugly. We had it removed. When the yard cut away the top of the tank about four inches of "mud" was found in the bottom. My guess is that the "mud" was dead diesel eating critters.

In place of the tank, I installed a sheet of marine plywood, suitably prepped, across the stringers. We use that for long-term storage under the bed platform. I will soon be moving the water heater from the engine room to under the bed which is another long story. I could have installed another water tank or a holding tank for the aft head using the separate fill and vent lines for either. But, I do not miss that extra 235 gallons. We still carry 720 gallons of fuel which gives us a safe range of 1,200 miles. I think 1,200 miles serves most here quite well. As for another holding tank, that would have been nice and still could be done. The flush from the head would be only a 10-foot downhill run and I imagine I could fit more than a 100-gallon tank there. Our holding tank is 45 gallons. A big plastic water tank would be nice also, maybe 200 gallons also easily plumbed into the system. We carry 350 gallons of water.

Boats - choices, choices, choices.

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Good post. Does make me wonder what range owners seek as a minimum, and why. For me on my little Willard 36, I just had the tanks replaced and was concerned about keeping 400g of diesel for a legitimate 1500 nm range. Why 1500? No good reason except it's the distance from Florida to Panama Canal; Panama to Acapulco, Acapulco to SoCal; and SoCal to PNW. Just seemed like a good number to breakup coastal cruising. Could be done with a lot less range, but would involve a lot more planning.

My sense is few powerboaters think in similar terms.

Peter

For me, as long as fuel range is enough to cover the longest hop between fuel stops that I'd ever conceivably have to make (with adequate reserve), then it's "enough". More may be nice, but it's not necessary. In many cases, water capacity (unless you have a watermaker) or space for provisions will limit when you have to go somewhere to reprovision long before fuel does unless you're trying to cover a lot of distance and on the move almost constantly.

My boat carries 420 gallons of fuel, but figuring the last 20 gallons are unusable and a 25% reserve beyond that (so 300 gallons planning fuel), my range is only about 160 miles on plane or about 350 at low speed in calm-ish conditions. Rougher conditions could easily knock the low speed range down to 300-ish miles. So it's got enough fuel to go basically anywhere in North America, with the exception of possibly being a bit short for the Alaska jump. Good enough for my use though.

I only carry 65 gallons of water though. There's room to upgrade the tank to something in the 90 - 100 gallon range, but the fuel tanks would have to come out to do it. Not really any good place to add a second tank of more than a few gallons without weight distribution concerns or it being in the way, unfortunately. The 70 gallon holding tank is great, however.

It sounds like a good plan to me. Unused diesel fuel is not an asset, it is a liability. It gets old and eventually will cause you problems.

pete

rslifkin said:

For me, as long as fuel range is enough to cover the longest hop between fuel stops that I'd ever conceivably have to make (with adequate reserve), then it's "enough". .................

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Post 25 sums it up for me too. Also mentioned here in PNW cruising grounds 2-3 fuel stops are passed with the capacity. But in passing by these fuel stops, also pass by refilling water tanks.
If the goal is to travel all day, every day then more fuel than water is needed. In our case we travel between stops where we will stay a few days at a time and therefore we use less fuel and need more water. Fuel capacity can be less and water increased.

Is it possible to replace with a new tank of equivalent size that you could use for water that a future owner could re plumb and use for fuel if they so desired?

johnrupp said:

Is it possible to replace with a new tank of equivalent size that you could use for water that a future owner could re plumb and use for fuel if they so desired?

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johnrupp, that's sort of what I have in mind. I had not considered selecting a tank that might serve either purpose, but I would certainly leave the fuel lines in place so swapping out my new water tank and storage for a new fuel tank would be a pretty easy job for a future owner. So, in a way, I would be completing part of the job of getting rid of an old fuel tank and prepping for a new one, if maximum fuel storage was a future owner's concern.

Two more thoughts on this.

Water maker -- I appreciate the benefits but don't think that is my answer. The fact is, neither water or fuel are too far away where we cruise. We anchor quite a bit, so we run out of water before fuel, but it's still not far away. I don't think I could justify the expense of a water maker, and in a lot of the places we go I am not sure the water is satisfactory for that anyway. With no need for it, I don't think I want an additional system to maintain either. Simple seems better to me. If we spend a few weeks in the Bahamas, I know that will be an exception and we would love one there.

Water to fuel ratio -- The reason this change might make sense on this boat is because the boat is basically a '43 Albin that Albin modified to come up with the '49. It has all of the fuel and water capacity of a '43, plus they added 2 additional fuel tanks under the cockpit extension (which is what makes it a '49). This change added significant fuel capacity, but water stayed the same. Therefore the ratio is such that adding water capacity in exchange for fuel capacity still seems to leave more fuel (cruising range) that one needs in this style boat.
The current fuel to water ratio is 4.375 to 1. While I had never looked at that ratio before, compared to those who have responded, I think it is a factor in making this change.