Spare Fuel Tanks and Connectors

Andy · 10 February 2003, 19:42

Hi,

I wish to carry a couple of spare fuel tanks in my RIB. The supplier of the boat has suggested that breaking the fuel line to insert a connector, that would allow the connection of the spare tanks is a bad idea. This is because the 200HP engine could suck air from into connector and into the fuel stream.

Anybody have any experience in this area?

Cheers

jwalker · 10 February 2003, 19:50

You need a tap in the main supply to switch it off when the auxiliary is being used and a tap in the auxiliary supply to switch that off when the main tank is being used. Or use a change over tap/valve.
An alternative is to use a standard male/female connector in the fuel line. Just separate at the main connector and plug in the connector for the auxiliary tanks. If you use the male end for the engine, the other connector will automatically seal. This arrangement allows you to connect any auxiliary tank you wish in the future.
JW.

Daniel · 10 February 2003, 20:17

Have done exactly this - can't see how there is any risk of air getting to the engine either?

I used the old-style Merc. connectors because they are available as male and female inline versions and inserted the 'join' near the engine but before the prime-bulge so that i can prime either supply - underfloor tank or spare plastic type. I did look at a three-way fuel valve, but could not see any advantage, infact the loose end (ready to connect to spare fuel tanks) would infact be a disadvantage. The way it is now i stow the fuel line for the reserve tank(s) under the seat.

Ribald · 10 February 2003, 20:53

Andy,

I had a fuel line made up for the plastic tank that has the same engine-end connector as the under-deck tank line. The plastic tank sits in front of the consul with a long line (inc. primer bulb) that will reach the engine. Therefore if any damage occurs to the main fuel line downstream of the primer bulb I am still covered.

Is your supplier suggesting that you change over tanks with the engine still running - doesn't sound like a good idea to me; could end up with a big BANG

Daniel · 10 February 2003, 21:27

Quote:

Originally posted by Ribald
could end up with a big BANG

Why? I've done that before, just be quick and give the bulb a gentle squeze.

Is this something i should not be doing?

Daniel

Ribald · 10 February 2003, 22:45

I only mentioned this as I have noticed that when I change over the fuel lines there is always a slight seepage of fuel.

I don't like the idea of petrol fumes near a running engine what with possible stray sparks around but perhaps I am being overcautious.

I have seen two boats (albeit with inboards) burst into flame whilst the owner was playing with the fuel lines when the engine was running.

Daniel · 10 February 2003, 22:50

Been there, done that as they say.

Several years ago i had an old (1970's) Mercury Blue-Band 65hp which was a real pig to start at the best of times.

Having turned it over and over and over i was investigating the fuel line when the main battery cable burst into flames (had overheated due to being in constant use for 10 minutes) ARGH - jumped overboard very quickly! The boat survived and, with a newer Yamaha engine lasted several more years.

Still, we learn from things such as this - what have i learnt? Own a newer engine that'll start easier

Phill · 11 February 2003, 11:25

I've put a separate, large, filter/water trap in the system and simply put two fuel leads into it, one out. No problems - even when only carrying one tank.

Scubakid · 11 February 2003, 12:09

Hi

Go down to Aladins cave (at Burlsedon, Southampton) they do a great valve which has 3 in an one out and is a rotary system so only one input is connected at a time this can be mounted on the console and changed at any time even with the engine running.

Hope this helps

John

LURCHER · 11 February 2003, 14:04

I run my Evinrude 115 ficht on plastic tanks and use the same old Mercury connector , works fine .I took out the built in tank as it was so difficult to fill and i take the plastic tanks to the garage to fill .

Garygee · 11 February 2003, 20:24

Hi folks

Just a thought, most fuel lines have connectors with spring loaded sealing ball to stop the petrol leaking OUT.

It would not much suction to pull IN this sealing ball and get air is the system.

In this way the seal is trying to work wrong way round

Regards Gary

Phill · 11 February 2003, 23:54

Quote:

Originally posted by Garygee
Just a thought, most fuel lines have connectors with spring loaded sealing ball to stop the petrol leaking OUT.
It would not much suction to pull IN this sealing ball and get air is the system.Regards Gary

If you need the amount of suction required to open the spring you also need :-
I) a larger diameter fuel feed system ;
II) a new fuel pump in a few hundred miles:

Orrr maybe you're spring's bust ?

Pete7 · 12 February 2003, 16:12

The ball is held open by the brass rod on the male connector, how ever on a rib with a big petrol engine the point of having large fuel lines is a very valid point

Pete

Andy · 12 February 2003, 18:45

Ok, its sorted. A 3 way cock valve will be inserted inline from the main tank, hence the main tank has the best fuel flow to the engine. Backup tanks on the deck will each have a female yam fuel conntector, and I will dangle a tail with a male connector from the fuel cock. This will alow the switching in of a single tank. These tanks can be unplugged and swaped as required.

However:

Its not likely that these 30l deck tanks will give as much fuel flow as the main tank and so I expect to loose top end and maybe some pickup. For cruises this will not matter.

I think I have also solved the loss of 500rpm off the top end of my other boat ... started last year just after I added connectors inline so that I could flow the deck tanks through the water serperator/filter. The problem - FUEL FLOW!! The connectors restrict the flow at max performance.

Its been an interesting journey! But it's solved now. Thanks for all the advice.