Fuel Line Length

[therrick]

I've got one of a few C-Dory's made in 1984 with a fuel tank located under the V-berth space. I cleaned the tank, cut an inspection port, installed a fuel gauge sending unit, and reinstalled the tank. Now, as I read through my Honda 90 Owner's manual, they mention that the fuel tanks should be located within three feet of the engine so as not to tax the fuel pump. The fuel line from the tank to the engine will be something around 16-feet.

The tank was installed by the factory so I figure that someone there gave it some thought before they put it in. But those were the early days and apparently only five were made with that option. I like the ideas of more gas and more weight up front, but don't want to have to carry a replacement fuel pump or two for the other conveniences.

It seems that if there is a problem, that it might be with the fuel line friction. Perhaps by replacing some fittings and going for a larger I.D. any potential problem might be overcome.

Does anyone have any expertise in this area? I sure don't...

Thanks,

Tom

[oldgrowth]

Tom – I think you have already figured it out. Put in a larger line and fittings in so more fuel can gravity feed to the back of the boat and the pump will not have to suck it as hard or far.

[Sea Wolf]

Tom-

I agree with Dave.

You could also go one step further and

1. Enlarge all the tubes and fittings

2. connect the front tank with a rear tank

3. let gravity refill the rear tank from the front

4. take fuel in directly from the rear tank, eliminating the long intake tube.


You'd have to vent both tanks, and also deal with surges and differences in elevation with the boat in the nose-up position when underway, which would probably help, but these problems seem solveable.

We talked about the friction of liquids in tubes at one point last year, but I can't find the discussion. The general concensus was that there was a lot more drag/friction on the liquid that most of us would expect!

Joe.

[oldgrowth]

Thank you Joe - you always explain things much better than I do.

[therrick]

Dumb luck strikes again. I had purchased replacement fuel line recently only to get home and find I had 20-feet of 3/8 instead of 5/16 inch. Perhaps that will be sufficient to overcome the internal friction. Now I just have to replace the fittings and the tank selector and ...

Not sure how the front tank would feed the rear. Both tanks will rest on the cored hull so should be relatively level. My limited understanding of a gravity feed would put the fuel line at the bottom of the forward tank, but since I'm still not fireproof I think I'll avoid that one. I'm sure there's a way but it escapes me unless it's to set up some kind of a siphoning effect.

Thanks guys for the input.

T

[doc]

An inexpensive fuel transfer pump should to the job.

[Sea Wolf]

doc- (and Tom)

I'm not sure what you mean by an inexpensive fuel transfer pump. Could you explain further?

I did think of a Bendix electric fuel pump initially, but the thought of one dumping fuel all over after breaking a fuel line was a bit un-nerving.

If one did put pick-up tubes in both tanks near the bottoms and connect them with a line/hose/tube with a typical fuel line squeeze bulb to start the gravity /syphon flow by eliminating the air in the system, I think you'd have a workable set-up, providing the friction in the check valve in the bulb wasn't too great.

Joe.

[SEA3PO]

Make sure that the fuel line is Marine grade fuel line....most fuel line is not...and if your boat catches fire your insurance company will not pay if you used automotive fuel line.... Marine fuel line is usually grey colored and MUST be used anytime fuel is transfered under decking or through bearthing spaces.... it is huge when compared to automotive fuel line...and will not burn.. to test this I tried to burn a hole through some with a acetylene torch...could not do it...all it would do is char...yet remained intact... it is really expensive...but I think it is worth the extra money. Also use Marine fuel fittings...they are longer and seal better, usually attached with 2 hose clamps.
I think it is legal to use automotive fuel line in exposed areas or in an open boat... I just would not use it where the fuel travels through the cabin.

Joel
SEA3PO

[therrick]

Since it's not gray in color, I just went back out to check. According to my dealer, the Bombardier fuel line I have is A-1 marine grade product. They said that the Quicksilver fuel lines are the gray ones that they know of. I've not tried the torch test, but the wallet test gave some indication that it's marine grade. I wanted to make sure that what I ended up with was in fact marine grade since it will be running through the cabin, although protected in a grounded PVC sleeve. I planned on running it in a single piece from the tank to the multiple tank valve. And all clamps will be stainless steel; the originals (?), or replacements, were definitely not.

In regard to pumping or siphoning from one tank to another, that might be the way I have to go, but I'm trying to keep it as simple as possible. I'm hoping that a larger fuel line running over the long distance from the tank valve forward will keep the engine's fuel pump from overworking. But that's just hope and without any empirical evidence to back it up. Perhaps it's time to call a Honda shop. Not too many of 'em in this state...

Thanks for giving me more to consider. I may actually understand this issue one of these days.

T

[thataway]

Most marine grade fuel line I have seen recently is black. Be sure it is alchhol resistant with the new blends--you don't want problems. I would not use a transfer pump in this type of boat--too many potential probelms.
Most likely the boat has run for XX years with a simple diversion valve and it will run fine, one of the factors is the height of the motor above the tank--if the tanks are both level, there will not be all that much more "effort" required to pull the fuel the extra few feet.

[Almas Only]

If you buy it at West Marine, and it's called "fuel line", then it's marine grade. Although I don't know if the color is an industry standard, in practice, at least, based on what's commonly stocked, the gray line is Class B2, which is suitable for gasoline outboard applications. The black is A1, and suitable for gas and diesel, and inboard and outboard applications. Both grades are alcohol rated. If you're running from a bow tank, you should be using the A1 for the run which includes that inside the cabin.

I'm curious about the bow tank. How many gallons does it hold, and where is the fill located?

[Larry H]

Safety note,

The Coast Guard does NOT allow fuel to be under pressure except between the fuel pump(on the motor) and the carb or injection system. The gas hose inside the boat can be under suction ONLY.

On an inboard engine, the fuel line under pressure MUST be metal between the fuel pump and carb or injection pump.

DO NOT put a fuel pump in the cabin to push the fuel to the motor. If a boost is needed, put the pump in the splashwell or just inside the boot where the fuel line exits the hull, to PULL the fuel from the tank.

The o/b manuf will have a spec for maximum vacuum in the fuel line. When I was servicing outboards, I had a vacuum gauge that could be inserted in the fuel line at the motor connector to find out if there was a fuel line restriction. As I recall, the number was 4-5 in of mercury for the Evinrude/Johnson 2-cycle motors.

If anyone tries this, don't squeeze the primer bulb after the vacuum gauge is in the line to prevent damage to the vacuum gauge.

Large outboards(150hp and up) need the 3/8th size fuel line to prevent fuel starvation.

PS The Coast Guard says that the fuel line inside the hull MUST be type A1, with metal clamps.

[therrick]

Alma's Only:

It's a 28 gallon tank seated on the hull below the V-berth directly forward of the porta-potty nook. According to Mark Toland, there were about five C-Dory's made in 1984 with this option. The fill is on the starboard side in the walk-around at the forward edge of the cabin; it comes in just forward of the helm station. The tank vent is located in the hull just below the filler.

Larry:

Thanks for the safety note. I hadn't planned on any pump other than the one on the engine to move fuel, but didn't know about the reg. Yesterday I picked up a couple of fittings to accomodate the 3/8-inch line from the tank to the multi-tank valve. I've not done any line testing since I've only got pressure gauges, none for vacuum. Talking to the Honda dealer, they said they didn't know for sure, but based on experience there shouldn't be any problems. Pretty sure it won't starve for fuel though.

On a related note, while perusing the USCG Boatbuilder's Handbook, they mentioned that "Each “USCG Type A1,” “USCG Type A2,” “USCG Type B1,” and “USCG Type B2” hose must be identified by the manufacturer by a marking on the hose." I see nothing indicating the rating anywhere on the new line I got. Bombardier made the line and I talked to the local dealer who looked it up and assured me that it was an A-rated fuel line. Perhaps the other markings refer to Canadian regulations. Haven't followed up on that yet...

Tom

[oldgrowth]

Tom – the Honda outboard has a fuel pump that will pull the fuel from the bow of your boat without any trouble. I have a 50hp Honda on my boat and forgot to open the vent on my 6-gallon portable tank. The pump had enough suction to flatten the tank. When I realized it, the tank was as flat as a pancake.

[therrick]

Thanks Dave,

Luckily the original aluminum tank will have a permanent vent to keep that from happening. Nice to know that I needn't worry about the suction though.

Tom