To have dual fuel tanks? Or not to have dual fuel tanks? That is my question.

[Campbellcruiser]

Ok; so here is my dilemma. I have a 45 year old Islander 37MS and I believe the 480 litre diesel Tank is in need of cleaning. The tank is split into two with a port and starboard fill, pick up and return. Problem is it tanks me a season to use 1/2 of each tank and I hate leaving them anything but full over the winter. So now I have poor quality fuel which is probably full of bugs. I've used the fuel conditioners and biocides in it. It is causing the engine to have excessive smoking and the mechanic I consult with believes it is my fuel as I have done everything else (clean injectors, not loosing oil, ect).

So I am thinking of removing the large tank and putting in something smaller. We (wife and 3 kids) only go wishing the gulf islands and maybe down into the San Juans so I don't need a month worth of fuel. But because of the currents I do need reliability. Which brings me to my question. Should I install 2 tanks? Or go with a single? Or should I try and remove and clean my old one?




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[sanibel sailor]

Try running off a small jug of clean fuel. If the smoke does not clear, this might influence your decision

[Cheechako]

As long as you know you fuel usage, no problem with one new, clean tank vs two old dirty ones!
Or maybe two plastic smaller ones is an option too. Those tanks are pretty reasonable.

[Viking Sailor]

As long as your tanks are not leaking - I suggest that you consider a fuel polishing system that has an option to circulate the fuel between tanks. Fuel polishing systems really do work. Also, it will probably be less work and cost less then removing/replacing the tank(s).

[boden36]

I would favor two smaller tanks. Leave one empty. That way you will turn over your diesel more frequently. If you are worried that the empty tank will corrode, fill it with argon or co2.

Regards,
Richard.

[Campbellcruiser]

The tank I currently have is old, and way too large for what I need. I got a quote for fuel polishing; 1500, which includes cleaning the tank. For that I can buy new tanks! If I do it myself that would be more cost effective, but I think I'm the long run I am better off with a smaller tank.

Can anyone suggest a size? Based on cost I was thinking of 20 Gal.


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[Lojanica]

I have big tanks but most of the time I only need a little fuel so I plumbed in a line for a small portable tank. Therefore I always have fresh fuel. The big tank(s) I use for voyaging and at the end of the trip I pump out the remaining fuel into the portable tank(s) and burn it in my truck. Sounds like a hassle but you know what a real hassle is: having engine problems because of poor fuel.

If I was to store fuel on the boat and always filling the permanent tanks I'd install a fuel circulating and polishing system to keep it clean but my system works well. I have a pump installed inline and it is easy to pump the fuel out of the tanks and then add biocide to the small remaining amount.

[exMaggieDrum]

If you ever want to sell the boat, it would not sell with only a 20gal tank. A real deal killer. I understand your issue but it would take a very special buyer to want only a 20 gal tank. Something to consider. Using just one side of your dual tank would help but not sure how to best seal up the other one to keep it safe and sound. It might be OK just to empty and dry it and then seal it up.

[TrentePieds]

Originally Posted by Campbellcruiser

So I am thinking of removing the large tank and putting in something smaller. We (wife and 3 kids) only go wishing the gulf islands and maybe down into the San Juans so I don't need a month worth of fuel. But because of the currents I do need reliability. Which brings me to my question. Should I install 2 tanks? Or go with a single? Or should I try and remove and clean my old one?

Observe your "typical" fuel consumption empirically.

On a typical crossing of the the Straits of Georgia (West Van to any one of the passes) or on passage from Gibsons to Madeira Park my Vetus 3M-10 uses 2 litres per hour on the average, so at 5 knots for a 30NM passage, which is as much as I usually care to do in one day, I'll use 12L, say 3 gallons.

So for messing about the "Salish Sea", where fuel docks are a dime a dozen, how much capacity do I really need?

An "adequate" tankage for me would be 50L, say 15 gallons. giving me a maximum range of 125 NM. 125 NM is a run from West Van to Seattle non-stop, or a return trip West Van to Lund non-stop. So how much more do I really need?

A rectangular section tank, 30 x 30 x 55 centimetres will hold 50L if my math serves. That's roughly 1 foot x 1 foot x 1 ft 9 in. Not very big at all!

Small tank, always running on the top half, and keeping the filter fresh seems to do it for me. In a small tank the muck in it gets agitated when pressing up and goes straight to the filter. Filters are cheap, engines are not,

Small tank, pressing up every day or two, means that fuel doesn't have an opportunity to go "stale" before it gets used.

From your home port to Vancouver/False Creek is a tad under 100 NM. But your engine is prolly a 4108, so you might like to carry twice the fuel I do to obtain about the same range. If you plan to go north, you should add some, of course :-)

TrentePieds

[Campbellcruiser]

TrentePieds, I was thinking the same thing. From Ladysmith to False Creek its 36 NM. A 20 U.S. gal tank is about 75 L and my Perkins 4.107 burns about 2.8l per hour doing 5knots (from all the info I could find). Which means I would use about 20 L. And if that seems small I will have ample room for a second tank.

The current tank has to go, it's too large.

The biggest reason I was concerned about having 2 tanks was for the safety factor. If I have a bad fuel issue I could just switch tanks, however, after thinking about it that seems highly unlikely.

Thanks for everyone's help.


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