Tips on replacing fuel tanks

Do I actually own the only boat on here where both the engines and tanks can be removed without cutting new holes in the boat? Mind you, none of it is exactly easy on my boat, but it can all be done non-destructively with adequate effort applied.

rslifkin said:

Do I actually own the only boat on here where both the engines and tanks can be removed without cutting new holes in the boat? Mind you, none of it is exactly easy on my boat, but it can all be done non-destructively with adequate effort applied.

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Well - you may not have plastic covers over your engines' pully's and fan belts... but, the good ol' Chris Craft designers/builders sure did a good thing to give you features of relatively easy access to engine and tank replacements.

We can "sneak" our Tolly's engines and tanks out the starboard or port side of salon's BIG window holes. However, to get tanks out from under the saloon sole would be a bear... even after getting engine out of the way.

Plan I've mused: If perchance tank replacement need happens during my ownership stint. Attach a rented Industrial Vacuum Pump to gas tank [already completely filled with water] and proceed to internally create minus air pressure for collapsing the tanks.

That I believe would greatly reduce efforts for tank removal. Being they are "Gasoline" tanks - EXTREME caution would be the name of the game!!

When wooden boats were scrapped most times the water and fuel tanks were in prime condition , and the tanks were still fine ., 30-40-50 years old.

MONEL was the material they were made from .

Monel is very easy to work with as it does not need to be welded to seal or create mounts..

The cost difference is a concern only to the boat assembler , not to the first purchaser who would hardly notice much difference.

FF said:

When wooden boats were scrapped most times the water and fuel tanks were in prime condition , and the tanks were still fine ., 30-40-50 years old.

MONEL was the material they were made from .

Monel is very easy to work with as it does not need to be welded to seal or create mounts..

The cost difference is a concern only to the boat assembler , not to the first purchaser who would hardly notice much difference.

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Monel was lauded as the best marine metal for all sorts of items when I was working on wooden boats in the 60's.

A good read: https://en.wikipedia.org/wiki/Monel

FF said:

When wooden boats were scrapped most times the water and fuel tanks were in prime condition , and the tanks were still fine ., 30-40-50 years old.

MONEL was the material they were made from .

Monel is very easy to work with as it does not need to be welded to seal or create mounts..

The cost difference is a concern only to the boat assembler , not to the first purchaser who would hardly notice much difference.

Click to expand...

Hi FF,

I'm going to go out on a limb here, and guess that you've never personally had a replacement fuel tank actually fabricated from monel in this modern day. If you had, I presume you've had the deep pockets to support the 10X cost of raw sheet stock versus aluminum. Only titanium is (marginally) more expensive (14% more than monel). And you've had the wherewithal to locate a fabricator willing to deal with the handling and forming costs (something like 5X over aluminum) associated with monel tankage. For instance, as monel work hardens (and subsequently cracks if not accomplished judiciously) upon bending, it is virtually impossible to form a rectangular tank without 100% welding each seam.

"...easy to work as it does not need to be welded..." Hardly.

"...The cost difference is a concern only to the boat assembler , not to the first purchaser who would hardly notice much difference." Seriously? Your conclusion is questionable, given today's realities of material and fabrication costs for the general public.

It is undeniable that monel makes a "better" diesel fuel tank. However if your only metric for "better" is based on your personal experience with a vessel originally fabricated for the US Government under contract by a boatyard contractually obligated to fabricate in full compliance with all military specifications and standards, for an entity with perhaps the deepest pockets of us all (the US Government), then I'm afraid we must agree to disagree on the definition of "better". Or if your metric is based on observation of tankage out of wooden boats fabricated a half-century ago in a vastly different economic climate.

Heck, the old-growth redwood my grandfather delivered to Australia at the turn of the 20th century (much probably still in use today) is "better" than the redwood I can acquire today. So what?

Personally I would love to have the wherewithal to specify monel fuel tankage in a new-construction custom motoryacht. But the reality for me, and I expect the vast majority of readers of this forum, is that new construction (production or otherwise) is not the norm. And certainly not "cost is no object" new construction. Rather we must confront the realities of the day, and do the best we can to reach a balance between "best" and "good enough". Unfortunately, monel fuel tankage falls far, far to the outside of what is financially approachable for me, at least.

As with all things, your mileage may vary with this topic. Should you have the wherewithal to afford monel replacement tankage in your boat, go for it. My pockets are shallower.

Regards,

Pete

"And certainly not "cost is no object" new construction. Rather we must confront the realities of the day, and do the best we can to reach a balance between "best" and "good enough". Unfortunately, monel fuel tankage falls far, far to the outside of what is financially approachable for me, at least."

I always assume the new boat assembler will shop for the custom parts required , so will not have to pay for the tank builders learning curve more than once.

Yes, monel is more expensive than plastic , the usual second choice , but the ability to install a deep bailable sump , means clean fuel forever ,no water, no bugs , no "polishing ", even after many decades, should have value especially as the boat gets older.

I have not built a fuel tank, but on WWII troop ships the toilets were monel , with a constant water flow for #1 and a pull chain for a big #2 flush. Great for 5000+passengers.


I have rebuilt a few to work as boat heads a with an Edson bronze pump they are superb for overboard flushing.


Here is a source of new monel to obtain pricing.

https://www.americanspecialmetals.c...MIgpfmwbDa7wIVx9rICh0mRQ9dEAAYASAAEgKdG_D_BwE

The author is an experienced how-to journalist, however, this article misses the mark in several ways.

"Nevertheless, I’d restrict fiberglass tanks to diesel fuel, just to be safe. And even then, maybe not."

And even then maybe not? Why not? Fiberglass is perhaps the best material for diesel tanks, bar none. I've cleaned out 30 year old FRP tanks on Hat's that looked like new when finished, what other material can boast of that sort of longevity, durability and accessibility? The plastic the author touts? Plastic is fine for gasoline, however, it can't be fully baffled, at least not roto-molded plastic, the kind that's seamless, and it can't be equipped with inspection and clean out ports, so what do you do when a plastic diesel tank becomes contaminated? He could have pointed out that FRP tanks are expensive and not easy to manufacturer, not as easy as steel and aluminum. He could also have pointed out that plastic fuel tanks are available in a range of sizes and shapes, but they cannot be custom made, at least not when roto-molded. Fiberglass and metal tanks are fully customizable.

"The classic scenario, and one I’ve experienced myself, results from water leaking through the deck or around the fuel fill, and puddling on the tank top. Since the tanks are usually tucked under the side decks and with little clearance between tank top and deck beams, only the most scrupulous owner will discover, and dry up, this damaging puddle"

He is right, that is a classic scenario, however, if the tank is ABYC compliant the top will be sloped to prevent water accumulation, and the water will run down the inboard side of the tank, where it will hopefully be noticed before it damages the tank.

"Most fuel tanks last for 15 years, maybe 20, if properly installed and maintained."

Hogwash, I routinely encounter metallic tanks that are over 20 years old. FRP tanks, if properly built and installed, will last the life of the vessel.

"Corrosion isn’t limited to black iron. Any metal, even aluminum and stainless steel, will crevice-corrode if water gets trapped against it without exposure to fresh air."

Aluminum suffers from poultice, not crevice corrosion.

" I’d have the builder use thicker plate than required, for added corrosion protection."

He got that right.

"Every tank meeting USCG and EPA requirements must carry a label, affixed to the tank so it’s clearly visible, attesting to the tank having passed the appropriate tests mandated by the Code of Federal Regulations 33 CFR 183 Subpart J - Fuel Systems."

So if it doesn't meet USCG and EPA requirements it doesn't need a label? I think what he meant to say is that all gasoline tanks must meet USCG, EPA, CFR regulations, and this includes a label, and that label must include, among other things, the tank material and thickness, test pressure, intended fuel and manufacturer, and the label must be visible after the tank is installed.

I have nothing against plastic for gasoline tanks. For diesel tanks, especially larger ones, if you want to be able to clean it out, go with 1/4" aluminum or FRP. Make certain the tank is properly installed, especially for aluminum, ensuring it is not standing in water, being dripped on or in contact with anything that will retain or trap water.

Inspection ports can be added to most tanks, except plastic, only on the top for gasoline, top or sides for diesel.

My take on the subject, for diesel tanks https://stevedmarineconsulting.com/fuel-tank-installation/