Jump to content

Fuel tank issues in Bluejackets


Recommended Posts

Good looking boat, the devil is in the last details and they seem to keep on coming.  An option for the gas tank ventilation is an aluminium tank which I believe doesn't require ventilation.  

My tank stinks when the boat is parked inside.  I haven't noticed any smell when the boat is parked outside.  It is a Moeller plastic from early 2012 before the extra coating regulation.  For your boat could you make an intake through the access hatch in the cockpit floor going to the hull exterior.  





Link to comment
Share on other sites

I have a Moeller of the wrong vintage, thanks to ethanol, and get the smell too.  My current thinking of a retrofit of this tank is to seal the tank space  fore and aft and run a large PVC pipe cut into an arc in the V under the tank.  The pipe section provides ventilation and drainage through the tank space without interfering with the tank in any way.  Could be done just as well with a piece of plywood over the V, leaving room for the tank in its current location.   The Coast Guard says the tank is safe and there is no danger from the vapor leak, but I don't like it.  Don't notice any smell after opening the boat to a breeze, underway or in any breeze.

Link to comment
Share on other sites

i must have the same vintage Moeller tank - i notice a faint smell in the cabin after it is closed up for a day or two.  The smell doesn't bother me; it goes away as soon as the door is opened.  But, i can't seem to get insurance without a survey, and as i understand the regs, an enclosed fuel compartment must be vented.  i did get basic liability insurance, but plan to schedule a survey after a few more updates. Am I wrong about the requirement for ventilation? 

Link to comment
Share on other sites

Yes you do need ventilation with a plastic tank.  As I read it not with a metallic fuel tank.  I built a plywood box around the tank to minimize the ventilated space,

Attached is a PDF with backyard boat builders safety guidelines  This is the ventilation section, there is more in the document.


The Ventilation System Standard applies to all boats that have permanently installed
gasoline engines for electrical generation (generators), mechanical power or
propulsion (inboards and sterndrives). In some instances the standard also may apply
to boats powered by outboards (such as an outboard powered boat with a fuel tank
permanently installed in a compartment.
With certain exceptions, the Coast Guard Ventilation System Standard requires:
A natural ventilation system consisting of openings and ducts for any compartment
which contains, or is connected to another compartment which contains, a
permanently installed gasoline engine or fuel tank, unless certain portions of each of
the compartments are “open to the atmosphere.”
A powered ventilation system consisting of an exhaust blower and duct system must
also be provided for each compartment in a boat that contains a permanently installed
gasoline engine with a cranking motor (starter). “Open to the atmosphere” means a
compartment that has at least 15 square inches of open area directly exposed to the
atmosphere for each cubic foot of net compartment volume.
Except for compartments “open to the atmosphere,” a natural ventilation system must
be provided for each compartment in a boat that –
- contains a permanently installed gasoline engine;
- contains a permanently installed fuel tank and an electrical component that is not
ignition protected in accordance with the Electrical System Standard (see page 35);
- contains a fuel tank that vents into that compartment; or
- contains a non-metallic fuel tank.
The “Natural Ventilation System” must consist of:
(1) supply opening(s) or duct(s) from the atmosphere or from a ventilated compartment
or from a compartment that is ventilated to the atmosphere; and
(2) exhaust opening(s) into another ventilated compartment or exhaust duct(s) to the
- Each supply opening must be located on the exterior surface of the boat:
- Each exhaust opening or exhaust duct must originate in the lower third of the
- Each supply opening or supply duct and each exhaust opening or exhaust duct in a
compartment must be above the normal accumulation of bilge water.
- The minimum internal cross sectional area of each supply opening or duct and
exhaust opening or duct must exceed 3.0 square inches.



Link to comment
Share on other sites

The way I read it is that natural vents in and out of an otherwise sealed compartment holding a fuel tank is fine.  I already have the outlet vent installed and could make both fairly easily.  Most of the verbage is reserved for inboard engines where requirements are much more strict.

Link to comment
Share on other sites



A powered ventilation system will take care of any safety issue, which the USCG says does not exist with the smell from the Moeller tanks.  It will not affect the smell that accumulates in boat storage unless you leave it on, which I assume you do not plan on doing.  I don't think that is a good solution.  I have asked the CG about a brushless solar fan on the output vent but they did not offer an answer.  That seems like a good answer to tank space ventilation to me but I maybe it has to make it's way through a few years of bureaucracy first.

Link to comment
Share on other sites

Gas tank ruminations:

Two years ago was the last time I read the USCG promulgated regs on gas tank installations. Heavy reading featuring plastic tank permeability ratings interacting with tank compartment volume as the prime determinates whether the tank compartment needed ventilation. I made no attempt to do this analysis as I lack both the mental capability and the patience.

With some plastic tank manufactures now conforming to CARB standards, permeability is reduced so there now be some relief on the ventilation issue. I remain steadfast in my understanding of the regs that a metal tank compartment needs no ventilation.

When Ed F. had his BJ 27 surveyed for insurance purposes, I recall the surveyor was hard over that the gas tank compartment had to be watertight. Ed asks how was he supposed to ventilate a watertight compartment? Surveyor admitted his and USCG requirements were at odds. So Ed made his tank compartment watertight and he passed the survey. I'm not sure what Ed did about ventilation.

I offer the following information for prospective and ongoing Bluejacket builders. The ventilation issue steered me to an aluminum fuel tank. Via template dimensions matched my boat's dead rise, I had a 30" long 36 gallon tank fabricated for $440. I was able to specify where the tank top fittings would be which is important as the filler neck was designed to allow use of a dip stick and easy pumping out of sediment. I have had little success with the accuracy of electric fuel senders on boat tanks.

The fabricator coated the exterior of my tank with two coats of epoxy for corrosion protection. Plastic tanks don't corrode. A couple of years ago, a USCG sponsored study suggested that if phase separation occurs in ethanol laced fuel, there may be some electrolysis occurring in an aluminum tank. I don't recall whether this concern was based on a theory or testing. Of course the tank fabricator

denied any knowledge of this potential issue. I'm planning to keep stale gas out of my tank.

Anyhow, you pick your poison on what route you wish to go in regards to metal versus plastic fuel tanks.

Link to comment
Share on other sites



You did your study as well as anyone can be expected to do, given the obtuse interpretations that we seem to get when a question is asked about this subject.  I too, like aluminum tanks for several reasons.  First and for some people, most important, is that the volume efficiency of a custom tank is way better than any off the shelf model.  That means that fuel capacity in the available space can be greatly increased, sometimes doubled.  Aluminum tanks can also be well baffled which almost stops surges before they can get started.


If an aluminum tank is coated with something like two coats of Interprotect and suspended off the hull, external corrosion is virtually nil.  Keeping fuel containing ethanol to a minimum in storage is good practice.  Not what we used to hear but today's gas is not what we used to buy whether it contains ethanol or not.


I think this deserves a thread of its own.  Anyone savvy enough to transfer all the posts to a separate one??

Link to comment
Share on other sites

This is tank that I am actually taking out to reinstall a larger one for a bigger hp engine. Its a rough shot of the saddle setup with the Interprotect coated fuel tank. I will try to find the install shots later on. Hopefully you can see the clearance around the tank.  Any and all water in the bilge can run fore and aft, if you have a bilge area without a problem. These aluminum tanks will last a long time without all of the gas fumes that still continue to plague the plastic ones.


Link to comment
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now

Supporting Members

Supporting Members can create Clubs, photo Galleries, don't see ads and make messing-about.com possible! Become a Supporting Member - only $12 for the next year. Pay by PayPal or credit card.

  • Create New...

Important Information

By using this site, you agree to our Terms of Use.