fuel tank location and size

[darrenwest1]

so yesterday I collected my first rib
a 2010 humber 5.5 with a mercury 4 stroke 60hp efi outboard that looks almost new .

BUT a previous owner has cut a hole under the helm seat and wedged a 25l tank in there , I doubt that will last very long at all

there are 2 of them silly saddle seats 1 at the helm and 1 near the back
I would like to rip out the rear seat nd replace with a double allowing 100l fuel tank under it , will this make a massive difference adding 100 kilos to the rear of the boat ?
thanks

[smallribber]

Originally Posted by darrenwest1

so yesterday I collected my first rib
a 2010 humber 5.5 with a mercury 4 stroke 60hp efi outboard that looks almost new .

BUT a previous owner has cut a hole under the helm seat and wedged a 25l tank in there , I doubt that will last very long at all

there are 2 of them silly saddle seats 1 at the helm and 1 near the back
I would like to rip out the rear seat nd replace with a double allowing 100l fuel tank under it , will this make a massive difference adding 100 kilos to the rear of the boat ?
thanks

A 60hp 4 stroke will run a long time on 25 ltrs. Might I advise that before you start ripping stuff out (which usually ends in tears) you try it as is. Most people have jocky seats by the way.

My 60 hp 2 stroke has a 32 ltr tank and in many years I have hardly ever needed more fuel on a normal day out. Just carry a spare 10 ltrs in a can

[darrenwest1]

I need to change the seats anyway as there are always 3 of us that go out , but was worried about adding more weight ?

[paulbrown22]

How neat is the hole/cut out? I believe Humber offered that as a standard thing if using removable tanks, so that might be how it was from factory. Certainly for a 5.5m having an extra 100l right at the stern, plus presumably the weight of two people atop the new double bench seat, will not be ideal and the boat will be very stern heavy. It might struggle to plane too as 60hp isn't much for a 5.5m when heavily loaded.

[paulbrown22]

I forgot to say as well, how far are you planning to go? I run my 6m Hardy with a 50hp with 2-3 disposable tanks totalling 65l, and depending on what I'm doing carry 1, 2 or 3 tanks. On our sailing club 5m RIB with a 60hp we have an under console 25l tank, and if it's a long race all the way downriver there's the perfect space between the console and anchor locker for a second identical tank, which allows us to swap the fuel line over within seconds. But 99% of the time we're running that with 1 tank, admittedly though we aren't blasting it at full speed all the time while on safety duties though!

[darrenwest1]

Originally Posted by paulbrown22

How neat is the hole/cut out? I believe Humber offered that as a standard thing if using removable tanks, so that might be how it was from factory. Certainly for a 5.5m having an extra 100l right at the stern, plus presumably the weight of two people atop the new double bench seat, will not be ideal and the boat will be very stern heavy. It might struggle to plane too as 60hp isn't much for a 5.5m when heavily loaded.

looks like he used a pick axe

[paulbrown22]

Originally Posted by darrenwest1

looks like he used a pick axe

Okay, I've seen some bad examples but Humber generally manage better than that! So presumably an owner "enhancement", or sold as a bare hull and fitted out by an "experienced" person...

[darrenwest1]

the cut lines are not even straight so deff not std

[Pikey Dave]

Unless you’re planning some extreme trips, you don’t need 125 litres with a 60hp 4T engine on the back.
Adding a double seat & 100 litres to the stern of a 5.5 will unbalance the outfit & turn it into a pig, you’ll never get the bow down & getting onto the plane with a relatively small 60hp will be a challenge. Holding it on the plane at low speeds in rough water will be a bigger challenge.
As previously mentioned, try it first before making any major changes, you might be surprised.

[Peter_C]

No way would a 5.5m boat come with only 25 liters of fuel from the factory. Triple that would be good. 100L is what my 4.5m boat carries. Does it have an in floor tank by chance? Common for an aluminum tank to fail and since it requires removing the console and cutting the floor open often they are left in place and a portable type tank is used instead.

Oh and yes 100L of fuel in the stern with two people will make a difference in a bad way.

[smallribber]

Originally Posted by Peter_C

No way would a 5.5m boat come with only 25 liters of fuel from the factory. Triple that would be good. 100L is what my 4.5m boat carries. Does it have an in floor tank by chance? Common for an aluminum tank to fail and since it requires removing the console and cutting the floor open often they are left in place and a portable type tank is used instead.

Oh and yes 100L of fuel in the stern with two people will make a difference in a bad way.

No way you need 100 ltrs with a 60 hp. It is way over kill. Just try it first with a spare 10 ltrs in a ordinary can

[darrenwest1]

How would I know if there is an under floor tank. I can’t see any holes that would allow it to be filled up

I think I can get a 70l tank under the main helm if I remove it then install it again over the tank. Would this be a better options ?

[willk]

Originally Posted by darrenwest1

so yesterday I collected my first rib
a 2010 humber 5.5 with a mercury 4 stroke 60hp efi outboard that looks almost new .

Congratulations.

Considering willk's law #2 and Humber's spec sheet, I would concur with Peter_C and his estimate of 100L (90L by willk's law). As you have a smaller engine (maybe a different hull) you could likely dial that back a bit and settle around the 60L mark.

I'd concur with the other posters who suggest trying her out for a day or so before making any decisions.

[willk]

Originally Posted by darrenwest1

I think I can get a 70l tank under the main helm if I remove it then install it again over the tank. Would this be a better options ?

I missed this - yes, absolutely the simplest solution, if there is a problem. I'd suspect that there isn't a below deck on that boat, but it's possible. There would have been a fill point, a vent, fuel riser at the engine, maybe an inspection hatch at the sender fitting - you'd see stuff I think.

[paulbrown22]

Originally Posted by willk

I missed this - yes, absolutely the simplest solution, if there is a problem. I'd suspect that there isn't a below deck on that boat, but it's possible. There would have been a fill point, a vent, fuel riser at the engine, maybe an inspection hatch at the sender fitting - you'd see stuff I think.

I think on those size Humbers any in built tank was typically in console/seat as opposed to under deck?

[paulbrown22]

Originally Posted by Peter_C

No way would a 5.5m boat come with only 25 liters of fuel from the factory.

Completely depends who specced it? On the new builds for our sailing club typically using XS 500's I explicitly remove the large inbuilt tank and have a single removable 25l tank as that's all we typically need 99% of the time, is much easier for the club to fuel up, and I don't want the hassle of failing in built tank in the future.

[willk]

Originally Posted by paulbrown22

I think on those size Humbers any in built tank was typically in console/seat as opposed to under deck?

Might explain the sawzall style hole in the console

[darrenwest1]

hey all , so after a lot of thinking and ideas regarding fuel tank . the helm has a large hole in the side as discussed earlier . ive found out I can install 2x 25l quicksilver ranks under there with a inch to spare . so after all the advice received here I have decided to do this , as for connections , any ideas do I just use one up then disconnect and re connect and use the other one ? I kinda like this idea as in theory ill always be able to get back to where I came from tide dependant . thoughts please ?

[paulbrown22]

Originally Posted by darrenwest1

hey all , so after a lot of thinking and ideas regarding fuel tank . the helm has a large hole in the side as discussed earlier . ive found out I can install 2x 25l quicksilver ranks under there with a inch to spare . so after all the advice received here I have decided to do this , as for connections , any ideas do I just use one up then disconnect and re connect and use the other one ? I kinda like this idea as in theory ill always be able to get back to where I came from tide dependant . thoughts please ?

That's exactly what I do with our club RIB and my Hardy - I have the tanks arranged and the fuel hose long enough that I can simply swap the connector between tanks without moving tanks around. On my Hardy I do have to remove a cushion and open a locker, so I keep meaning to build a fuel manifold with a switchover valve, but so rarely do long passages that need more than 25l before i get to my destination that job hasn't yet made the top of the list!

[willk]

I run this config on a pair of 23L plastic tanks supplying a 40hp 4 stroke. I didn't bother with a switch - I had one on a previous setup and it just complicated life - more joints to fail, things to jam. Most engines around that size are returning just over a Nm per liter over the day. 25Nm is a fair clip in a small boat - you'll know you've done it!

So yeah, manual swap of hose between tanks. I carry a spare fuel line assembly in case something calves. I would strongly suggest not waiting to run out of gas before swapping - apart from potential engine issues or stopping dead in front of the Calmac ferry leaving Oban (you know who you are!!), it's really not a good fuel plan. I would regard the last 20-30% of the tank as a reserve and swap over at that point. If you're retracing the route out, you'll theoretically have the same in the other tank as well. Weather and tide or a heavy hand can seriously effect fuel usage.