Opinions on fuel tank located in cabin?

M

mcauliffesean

New member
Hi guys,

My c-dory 18 has had a Boston whaler style fuel tank installed under the front bunk. I am a little worried about overnighting with 20 something gallons under me plus possible fumes. Also concerned about the weight considering that the original idea was to have them in the stern. If I remove the large tank the plan would be two 6 or 12 gallon tanks in the stern to run my 70hp. Thanks for the advise in advance. Do I leave it or take it out of the cabin and return to stock?
 
My CD 16 came with a Yamaha 50, two 6-gallon tanks and two Group 24 batteries under the splash well. It was designed for a Johnson 40 2-stroke, single 6-gallon and single Group 24. So that's an additional 150 lbs in the stern (and hanging off of the stern). In order to avoid having to mess with trim tabs, I moved my gas tank forward under the berth.

I now sleep above 23 gallons of gas, but my tank is post 2011 when the industry was required to use nylon lined tanks. No gas smell. With the old style tanks in the cockpit, I could smell gas when sleeping with the camper back was on. Moving the tank under the berth was an improvement in balancing the boat and smell. I don't think the stock arrangement was necessarily the best, especially if you "improve" things with a bigger engine, more gas, and a house battery.

Going from 20 gallons under the V-berth to 24 gallons in the cockpit will make a difference on an 18 foot boat. Before I moved my stuff, I used my brother as dead weight to see how much difference it made in boat trim when on plane. With him scrunched completely forward in the V berth, I was much more comfortable on plane in light chop (he wasn't). There are advantages to balancing the boat.

Mark
 
Mark, I second the balanced boat idea! The 19s are notoriously stern heavy. I finally put about 100 lbs of lead ingots under my anchor rode. The ride is greatly improved.
 
From the US Coast Guard's "A Boaters Guide to Federal Requirements for Recreational Boats":

Ventilation (33 CFR 175/183, 46 CFR 25)
Boats that use gasoline for electrical generation, mechanical power, or propulsion are required to be equipped with a ventilation system
A natural ventilation system is required for each compartment in a boat that:
• Contains a permanently installed gasoline engine
• Has openings between it and a compartment that requires
ventilation
• Contains a permanently installed fuel tank and an electrical
component that is not ignition-protected
• Contains a fuel tank that vents into that compartment
(including a portable tank )
• Contains a non-metallic fuel tank
A natural ventilation system consists of:
• A supply opening (duct/cowl) from the outside air (located on the exterior surface of the boat), or from a ventilated compartment, or from a compartment that is open to the outside air
• An exhaust opening into another ventilated compartment or an exhaust duct to the atmosphere
Each exhaust opening or exhaust duct must originate in the lower one- third of the compartment Each supply opening or supply duct and each exhaust opening or duct in a compartment must be above the normal accumulation of bilge water
Click to expand...

This means if you put a tank in your enclosed cabin, without the proper vents (because none of the electrical circuits in the C Dory Console are ignition protected), you have to have the proper ventilation system.

I am not comfortable with potential explosive fumes inside my cabin--unless I have a sniffer in the bilge.

My feeling is that if one wants to put the bow down more (and there are certainly times when that is necessary), a combination of trim tabs and a Permatrim foil on the outboard are the best way to do this. The reason, is that although when going into chop you want the bow down--when running down seas aft of the beam, having too much weight in the bow, will cause the boat to "bow steer" or broach. Both of these can be potentially dangerous handling situations. My current 22 had 100 feet of chain in the anchor locker. First thing I did was to get rid of this.
 
I jumped to quick on fuel tanks. I do not like in cabin and bunk. It is sad though
that most boat builders/designers do not take into account weight in balance. When flying
I was very sensitive to this issue as can cause planes to stall. My 23Venture is a bit
to heavy in stern with 60 gallons of fuel, three batteries.. The Perma Trim tabs
I put on the two 50 Hondas have helped a lot. The Venture of course has
a different hull designs than most C-Dorys and tolerates it more. So with ref.
water tank, and gear and two people in helm and navigator seats it does
pretty well. If i had put adjustable trim tabs could have forced bow down more.
But forcing is key word it is not a substitute for proper balancing. I have seen various C-Dories sitting high bow at the dock. Often when bigger engines than
designed for have been added. Takes a lot of experimenting to get it right.

I am sure my comments have offend someone and not meant to. Just 40 years
of my experience in small boats. But years does not mean good experience.

This is a good issue to discuss. I still think it comes back to original design
not taking use into consideration as much as they should have.
 
When the first C Dory was designed it was for the 70 hp 2 stroke, and less fuel and batteries. The boats tolerate the weight, but Baxter is correct that the more modern design of the 23 gives it more beam aft to tolerate weight better. I am as guilty as anyone, since I often run with the boat very heavily loaded. Example on the St. John's trip this year, where I started cruising at about 17 knots and after about 3 weeks with food, water and fuel decreased, but with still 2 chest freezer/refers (almost empty), 3 group 31 batteries and some other "junk". We were cruising at 22knots at the same RPM.

I believe that the 18 was first sold mostly with a 50 hp to 70 hp outboard. Currently they are powered with from a 50 to a 115, with the most common being a 70 hp. The Toland 18-8 were powered with a 45 hp initially.

The beam of the 18 and 18-8 is 7'3", on the 19 and 22 it is7'8" and the Venture 23 beam is 8'. The virtue of light boat, and not putting a heavy engine/batteries is well made. This has been discussed, along with the running attitude of the boat vs sea conditions and trim. My personal choice is to go with the trim tabs and Permatrim, for several reasons, perhaps not the least is that I may run by boat very light around home, and loaded when on a longer cruise. Around home even with a light boat, I find that the fine tuning of tabs and a Permatrim, makes for a better ride.
 
Some of the cape cruiser boats had the water tank up front (20-25 gallon ?) which helped in getting on plane with 60 gallons of gas in back and with 2 group 27 batteries Thats a lot of weight plus a big 4 stroke engine .
My hull #3 came with the port side 20 gallon water tank I was going to change it to under the V-berth but decided against it .
The boat planes off at 10 mph with trim tabs down and engine trimmed in (no foil or permatrim on engine )
 
Thanks for all of your opinions. I think the best thing for me is to remove the tank and go back to the stern located portable tanks. It is unfortunate because the tank fits so well, etc. This is the safest route with two little kids looking for every opportunity to sleep in the cabin. BTW I found the previous owner used clear vinyl tubing as vent line and it had a pretty good pinch.
Thanks again,
Sean
 
mcauliffesean":gwoa6bvi said:
BTW I found the previous owner used clear vinyl tubing as vent line and it had a pretty good pinch.
Sean
Click to expand...

Good find! Thanks for bringing that up because it brings to mind several other requirements: --and just a reminder that only fuel line rated by USCG for gasoline with ethanol should be used in all of the tubing in the fuel system. The usual designation imprinted on the house should be "USCG Type A1-15" or "ISO 7840-A1" There should be a week and year stamped on the hose. This type of hose is ethanol resistant--which many of the older hoses were not.

Also note that all vent openings to the "outside" must have " Have a flame arrester that can be cleaned unless the vent is itself a flame arrestor" Generally this means a fine mesh screen, with adequate openings pointed downward and slightly aft.

A but more controversial, but still valid, is CRF Title 33,§183.568 Anti-siphon protection. Basically there is a requirement for an antiphon valve, if there is a chance that the fuel hose from the top of the tank to the carburetor or injection pump goes below the level of the top of the tank. In addition there is a requirement If the length of fuel line from the tank outlet to the engine inlet is greater than 12 feet, a manual shutoff valve shall be installed at the fuel inlet connection to the engine.

§183.572 "Grounding.
Each metallic component of the fuel fill system and fuel tank which is in contact with fuel must be statically grounded so that the resistance between the ground and each metallic component of the fuel fill system and fuel tank is less than 100 ohms."
 
The more forward a fuel tank is mounted in a power boat, the more violent the
fuel will be 'shaken up' when planing speed is reached. I don't like that idea much.
Actually, I don't like that idea at all. Same reasoning and conclusion for placing a
holding tank too far forward. This really stinks.

Aye.
Grandma used to say, "If your feet smell and your nose runs, you're going in
reverse."
 
Well it was not easy but I got the tank out of the cabin and moved all of the lines. Now I have to get a couple of 6 or 12 gallon portable tanks, move the battery forward, get a new forward hatch, and make some cushions and we will be ready for our first overnight trip planned in two weeks for my 6 year olds birthday. Thanks again for all the help and leading me to a decision!
 
One thing to keep in mind is that if you are going to have to lift your tanks in and out of the boat, a full 12 gallon tank weighs about 75 lbs. If that is the case, multiple sixes might be a better option.
 
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