Fuel Cell with 2 outboards

[SPLMAXSAM]

Over the next 60 days I am outfitting a new used fishing boat, 1984 Mirror Craft 17 foot center console. I have bought two rebuilt outboards, a 70 hp 2 stroke and a 9.9 hp 2 stroke. There is a 26 gallon fuel cell located behind the helm that came with the boat. It is currently not connected. The previous owner used small orange gas cans instead. I want to supply fuel to my 2 Merc outboards.

From the tank :
Copper pipe to under the floor
5 feet of 3/8 fuel line to
Fuel Water separator to
T fitting to
(1) gas primary bulb, clear filter OUTSIDE the 70 hp
(2) gas primer bulb, clear filter OUTSIDE 9.9 hp

I think the bulbs would act like a one way valve. The clear filters would show me gas flow. Both outboards use mixed oil/gas.

Would this be a good idea?


Second Problem

I have threee fittings on the top of the tank. One fitting is for filling the tank, the second fitting is for the outboards and the third fitting is for the fuel gauage.

Do I need to add some sort of vent?

 

[1fishbone]

Re: Fuel Cell with 2 outboards

1. Metal tanks need to be grounded, any copper tubing too.
(I heard copper is not good to use with gas, I've used it in cars)
2. one fitting for fill, one fitting to the filter/separator, one fitting for vent, the gauge is usually electric needing another larger hole.

The vent should go outside the hull, away from any source of sparks.
The tanks needs to secured with straps.
It would also be better if you mounted this tank below deck, fore/aft for better weight distribution.

 

[SPLMAXSAM]

Re: Fuel Cell with 2 outboards

Thanks

The tank is secure to the deck and is made out of Aluminum.

I will add a grounding strap .

The tank is the helm seat.. Where sould I vent it?

 

[Bob's Garage]

Re: Fuel Cell with 2 outboards

Are you sure this is a fuel tank for a boat?

The fill, vent and pickup tube are all at the same end of the tank. Seems to me that you either will get an incomplete fill, or poor fuel delivery whether you mount it side ways (which would be wrong due to sloshing) or inline with the keel.

As was mentioned, mounting the tank side ways could cause difficulty in controlling the boat due to fuel sloshing from one side of the boat to the other. And the rougher the seas, the lower the fuel in the tank, the worse it will be. Course this is just my opinion, based on conjecture, but it doesn't take much imagination to see the potential problems in your future.

And if you decide to continue with the project, I would add a 3-way fuel valve between the W/S and the 2 fuel lines, so you can make a physical switch between engine fuel lines.

 

[smallboatlover]

Re: Fuel Cell with 2 outboards

if this is a boat gas tank it should already have a vent if not you should install on to the top of the tank.

 

[SPLMAXSAM]

Re: Fuel Cell with 2 outboards

Thanks for the information.

Here is a picture from the side of the tank

I assume from the plate it is a marine tank
SPECS -
Made 2/19/1996
Material 0.125" Aluminum
26 gallons
5 lbs of test pressure
rated for gas

As I mentioned the tank is part of the helm seat. It is located 24-27 inches from the transom area

The previous owner used a small 3 gallon tank to run a Johnson Outboard

There is absolutely no room below the floor for a "belly tank" and there is very little room in the transom. If I am looking at something bigger than 3 gallon or I if I do not want a tank jutting into the limited floor splace, I ithink I have to start moving towards the bow.

Rough seas and sloshing
I can see your point. If I get the "pick up " on the bottom of the tank - DEAD CENTER IN THE MIDDLE, would that minimize the effects of rough sea?

 

[Silvertip]

Re: Fuel Cell with 2 outboards

A boat normally runs and even when sitting in a bow high attitude. That's why the pickup is at the back of the tank and also where the fuel will be most of the time, especially when the level gets low. Fuel going INTO a tank must displace the air that's in there so a vent is needed. Likewise, when the engines are running, fuel that is drawn from the tank must be replaced with air - again this is the job of the vent. Ever suck on a soda bottle and see the sides collapse? Same principle. I guess I would look at similar boats to see how they vent them. Venting into the cabin/helm area is not safe.

Running two engines from the same fuel feed is possible provided you use a fuel selector valve. The flappers inside a fuel line primer bulb will not do the job. Manual valves are not expensive. If you don't shut off the fuel line that is NOT being used, you can suck air from the carbs on the non-running engine. The needle and seat in a carb works on pressure INTO the carb. It will not prevent back flow of air in a suction situation.

 

[Bob's Garage]

Re: Fuel Cell with 2 outboards

Has this tank ever held fuel? Was it ever put into service on this boat? You may have problems getting someone to work on the tank if it ever held fuel. Don't know for sure, but it seems likely to me that a "pro" wont want to.

Some observations/suggestions;

It is not original to this boat (they probably just used portable tanks). It may be a Marine tank but it is not set up for installation in a boat in the customary manner. (i.e. no vent, do not see a normal fuel gauge access, the fill and pick up are at the same end of the tank. If the tank is mounted in line with the keel, the fill and vent would be forward and the pick up would be to the rear, gauge somewhere between. this way when the boat is running on plane or bow up the fuel goes to the rear of the tank.) It may be a tank for a large boat.

You could fabricate a pickup tube that replaced or extended the current one that reached the middle of the tank, but try to keep the end off the bottom to avoid sucking up contaminates.

A vent could be placed in the plastic cap (which looks like a plumbing fixture by the way) in the form of a brass fitting of the type used to vent a compressor. Get one that is as near the same size as the fuel line or the engine could be starved for fuel.

Ground the tank and solidly secure the tank to the floor.

Good luck!!

 

[SPLMAXSAM]

Re: Fuel Cell with 2 outboards

Thanks for the help. You got me going (hopefully) in the right direction

A) I never want to exceed 90% capactiy in the fuel cell. I think 20 gallons should be max out of 26 gallon capacity

1) Vent (fill, expansion & slosh) - build a vent that pssibly will have to extend towards the exterior of the boat

2) fuel pickup at the lowest point of the tank

3) fuel level sender will never be accuate do its mounting location.

4) add a cap to the filler

I will remove the tank friday. clean it and start working some ideas.

 

[Adjuster]

Re: Fuel Cell with 2 outboards

I have never seen anything like that before. Sure makes tank replacement easy if ever needed.