Advantages Of A Single Fuel Tank?

[ABfish]

My new to me Maritimo has a single fuel tank of 900 gallons. As I've gotten to know the boat, I see some advantages in this setup as the fuel piping and valving is much simpler, and the single tank can be filled from either side of the boat.

The single tank sits athwartship, forward of the engines, so I presume the trim of the vessel is only marginally affected as the fuel is consumed.

So, what's the conventional wisdom of a single fuel tank versus 2 or even 4?

 

[rslifkin]

Personally, I'm not a big fan of having less tanks than engines. With a single, 1 tank is fine. But with twins, I like 2 separate tanks, as there's less chance of a fuel issue impacting both engines simultaneously. Sometimes you end up with more tanks just based on what it takes to make the desired fuel quantity fit in the boat.

In your application, I'm hoping they at least put the pickups for the 2 engines at opposite ends of the tank to minimize risk of simultaneous clogging if you get junk in the tank.

 

[mvweebles]

The Willard 40 had a thwartship tank (aluminum), but I think most were dual tanks vs a single. It made for a relatively large engine room - I know of one that had a Splendide W/D in the ER.

Certainly would be handy to only have one tank - easier to make a polishing system as the plumbing is simplified as you note. But overall, I think two tanks have slightly more benefits than a single tank. If you need to repair a tank, you can move fuel to the other one. A leak in one can be isolated. Bad fuel sometimes doesn't affect both tanks equally. Also handy to trim the boat sometimes.

I'd be interested in a picture of your engine room since there are no saddle tanks. I believe larger Betrtrams also went with a thwart tank, though in fiberglass. I'm sort of surprised more boats don't have thwartship tanks.

Peter

 

[sunchaser]

Love Maritimos. One big tank for that boat makes a lot of sense to maintain trim as you note.

 

[tiltrider1]

I think the two vs on argument is very weak. The odds of fuel contamination hitting only one tank is pretty small. If this is any kind of an issue then I'd rather have one tank and a fuel polishing/filtration system.

The argument of having a second tank to off load the leaking tank into is also very weak. I have only found fuel leaks when both tanks were full. Technically I have 4 tanks but the reality is I have two sets of two. Each set is plumbed together with a 2" cross over pipe.

The best argument I can make is if you had to remove a leaking tank, I would replace it with two tanks and use a cross over pipe. This would make the installation much easier.

 

[Larry M]

I would have loved one big tank (we had 2-350 gal). One tank would be much easier to mange fuel. No valves to switch and return only goes back where it came from. A day tank would be nice but not necessary We had 2 tanks and trim was always a consideration, particularly when we did multiple day passages.

 

[ABfish]

Here's the engine room looking forward. Fuel tank is behind the Racors.

Battery banks are mounted outboard of the engines on both sides.

 

[Mako]

On on my big boat, I had a single tank of 1600 gallons under the aft cabin sole, completely sealed with no clean outs. Twin engines. I did not have a separate fuel polishing system but instead I had 2 Jimmies, which accomplished fuel polishing, in essence, because of their huge fuel return rate. I also used plenty of additives and filled up at the commercial docks where fuel turnover would be much higher than at little marines. I also had a penchant for going out in large seas so the tanks were quite stirred up.

Now planning a new-build, my thoughts/lessons learned go as follows:

• Single fuel tank with single engine;
• Will be located in a full athwartships location, as I hate saddle tanks in the engineroom;
• A completely sealed day tank (12 hrs);
• Fuel polisher... considering a centrifuge type because you can burn through dozens of valuable filters if you take on a huge load of crappy fuel;
• Clean out access to the fuel tank.

I believe this formula would work well, especially with a modern T3 engine which requires fuel to be ridiculously clean.

 

[psneeld]

My biggest issue with a single tank is you lose all your fuel (unless you have a great bilge, lots of filters and guts) if you have any issue with the tank and plumbing.

Sure it's a low probability, but it's greater than zero.

 

[diver dave]

I suffered a two gas motor flameout within a minute of each other. And, 2x carbs filled with water. And 2x racors filled with water.
Yes it can happen.

 

[High Wire]

I suffered a two gas motor flameout within a minute of each other. And, 2x carbs filled with water. And 2x racors filled with water.
Yes it can happen.

And that was with two separate tanks?

 

[diver dave]

It was one tank. Turns out it had a side wall corrosion hole, hidden behind foam. The rain water came in.

 

[Symphony]

Don't change anything on your boat for at least the first year of constant usage. Then you'll know what changes you want and their priority.

 

[Southern Boater]

View attachment 140858

Here's the engine room looking forward. Fuel tank is behind the Racors.

Battery banks are mounted outboard of the engines on both sides.

A great looking engine room, nice and bright, you can never have too many lights and visibility in this space, and as Maritimo are a very beamy boat, plenty of width to get around.
I can’t understand however, boat manufacturers installing the alloy “checker plate” flooring/sole in anything but completely stand-up engine rooms, this product is torture on your knees, in these low headroom engine rooms.

 

[psneeld]

Don't change anything on your boat for at least the first year of constant usage. Then you'll know what changes you want and their priority.

No boat is perfect and if you have a decent amount of boating experience, there are quite a few things needing to be changed ASAP.

A few that are comfort and a few that might be safety in your mind.

No sense in waiting to change those. But yes, you have to have the experience to know those that could/should be changed.

 

[O C Diver]

My only complaint from owning a single tank boat was that if running in beam seas, fuel tended towards the lower side exacerbating the list to that side. If I were going to own another single tank boat, the fuel tank would need to occupy less than the middle third of the beam.

Ted

 

[mvweebles]

My only complaint from owning a single tank boat was that if running in beam seas, fuel tended towards the lower side exacerbating the list to that side. If I were going to own another single tank boat, the fuel tank would need to occupy less than the middle third of the beam.

Ted

There are two issues. First, single tank. Second, midship/thwart tankage (either a single tank or twin tank as many W40s did). Many advantages to midship/thwart tanks. A single vs a twin tank is more difficult to advocate for.

Peter

 

[boomerang]

It was one tank. Turns out it had a side wall corrosion hole, hidden behind foam. The rain water came in.

Both engines cutting out within minutes of each other will make you sit up in your helm chair a little straighter. Gee wiz. You would've thought the racors woulda stopped the flow before the float bowls got contaminated...maybe gas is different.

 

[boomerang]

On on my big boat, I had a single tank of 1600 gallons under the aft cabin sole, completely sealed with no clean outs. Twin engines. I did not have a separate fuel polishing system but instead I had 2 Jimmies, which accomplished fuel polishing, in essence, because of their huge fuel return rate. I also used plenty of additives and filled up at the commercial docks where fuel turnover would be much higher than at little marines. I also had a penchant for going out in large seas so the tanks were quite stirred up.

Now planning a new-build, my thoughts/lessons learned go as follows:

• Single fuel tank with single engine;
• Will be located in a full athwartships location, as I hate saddle tanks in the engineroom;
• A completely sealed day tank (12 hrs);
• Fuel polisher... considering a centrifuge type because you can burn through dozens of valuable filters if you take on a huge load of crappy fuel;
• Clean out access to the fuel tank.

I believe this formula would work well, especially with a modern T3 engine which requires fuel to be ridiculously clean.

A day tank is high on our list of needs ,wants & desires for our next boat. That and the same amount of teak that comes in a small box of matches...

 

[rslifkin]

Both engines cutting out within minutes of each other will make you sit up in your helm chair a little straighter. Gee wiz. You would've thought the racors woulda stopped the flow before the float bowls got contaminated...maybe gas is different.

I think if you suck in enough water, it's possible to just pull it right through the filters once they're full of water, at least with gas.

 

[psneeld]

A day tank is high on our list of needs ,wants & desires for our next boat. That and the same amount of teak that comes in a small box of matches...

Always thought about putting a 20 gal day tank right above the Racors.... obviously not high enough on my "to do" list....

 

[diver dave]

A few days ago, wife and i doing a dive 15 miles off the st aug coast.
Light winds and 2-3 ft seas. Calm, except we were running a 17’ boat. With every wave, i worried the tank vent was ingesting seawater. This racor was only the thin metal can spin on style. No way to monitor any tank water.
Anyway, happy ending; but i replaced that style with the new SNAPP racor. Has a visible bowl and drain.

 

[C lectric]

No comments on the tanks and organization yet.

However about the comments about Checker Plate for floor boards.

Use Knee Pads. Good ones. The little cheapie foamies, I have found are useless and do not stand up for long.

I have been wearing leather pads for work, the boat , and the house for more than 40 yrs now. With them it takes a lot to cause me any distress. Without them it does not take much.

In fact I only bought the two pairs 40 yrs ago and still am using them.

They use heavy felt inside as the cushion.

They are Kuny pads made in Alberta. I have repaired them, the straps, with an old leather belt cut, punched and pop rivetted back into place.

And just for a recommendation more than once at work I came out from under a machine with a screw or two stuck into the knee pads. Had they gone through I likely would have been severely hampered for future work.
The screws never even got through. I am not recommending this as a test,
just my experience.

I keep one at home, retired now, and one on the boat. If a repair is needed then that one comes home and the home goes back to the boat.

JMO

 

[Southern Boater]

No comments on the tanks and organization yet.

However about the comments about Checker Plate for floor boards.

Use Knee Pads. Good ones. The little cheapie foamies, I have found are useless and do not stand up for long.

I have been wearing leather pads for work, the boat , and the house for more than 40 yrs now. With them it takes a lot to cause me any distress. Without them it does not take much.

In fact I only bought the two pairs 40 yrs ago and still am using them.

They use heavy felt inside as the cushion.

They are Kuny pads made in Alberta. I have repaired them, the straps, with an old leather belt cut, punched and pop rivetted back into place.

And just for a recommendation more than once at work I came out from under a machine with a screw or two stuck into the knee pads. Had they gone through I likely would have been severely hampered for future work.
The screws never even got through. I am not recommending this as a test,
just my experience.

I keep one at home, retired now, and one on the boat. If a repair is needed then that one comes home and the home goes back to the boat.

JMO

Yes, I’m a huge fan of the better quality knee pads, in fact just an hour ago I was jammed into a small section of the engine room (with my knee pads on of course) hauling on a tight fitted basin discharge hose through a bulkhead, using my elbows as lever points. Ended up putting another set of knee pads on my elbows to save damage (to me) on a metal syphon break.
I probably looked like a learner on a skate board

 

[Mako]

Polished aluminum plate looks nice, but you’re right that it’s horrible on your knees. My steel boat had steel checkered plate, painted boring white like the rest of the engine room. I bought some green felt carpeting off a roll at Home Depot. It was fantastic and looked great.

 

[Southern Boater]

Polished aluminum plate looks nice, but you’re right that it’s horrible on your knees. My steel boat had steel checkered plate, painted boring white like the rest of the engine room. I bought some green felt carpeting off a roll at Home Depot. It was fantastic and looked great.

I spend a lot of time in the engine room, I like being down there checking the systems and tinkering around, it needs to be comfortable and very well lit, like a hospital emergency room. I have tube matting underneath house carpet, very comfortable to kneel on, and I just roll it up together if I need to access the bilge covers below.

 

[ABfish]

Yeah, I have a couple of thick doormats that I move around in the ER. Much easier on the knees than the diamond plate.

 

[OldDan1943]

Smile Many boats run out of fuel because “someone” forgot to refill it.
I have 2 outboard tanks with the piping to cross connect (which I do) selectable returns or both. Selectable source to engine. IF, when you fill tanks, you get a load of bad fuel, the tank can be isolated and concentrate the fuel polisher on the contaminated tank.
Duel Racor filters with vacuum gauge with tattle tail.
I also put in a fuel polisher. Good for polishing and moving fuel at the dock.
Try not to make the piping and valving so complicated it is difficult to understand by the next owner.

 

[twistedtree]

Well suited for boat-yoga are, wait for it, yoga mats. Really, no kidding. They are reasonably priced and easily cut to fit any space. I have most areas of my ER and Laz lined with them.

 

[Southern Boater]

Well suited for boat-yoga are, wait for it, yoga mats. Really, no kidding. They are reasonably priced and easily cut to fit any space. I have most areas of my ER and Laz lined with them.

Good call TT, especially the 1/2” thick ones