I keep thinking of more and more questions

[Matt72]

Hi

 

Another couple of basic questions on cruisers :-

 

What sort of range do you get out of a petrol outboard on an inland cruiser and also how do you go about refuelling - ie/ from what I read you cannot get petrol canalside so is it a walk to the local garage or do you carry spare fuel on board?

 

Thanks

Matt

[twbm]

Size of engine and shape/size of boat will all affect the fuel consumption.

 

A walk to the local garage is OK if there is one.

 

Bottom line is petrol engined boats are a small minority on the canals for all the reasons that have triggered your questions.

[Matt72]

Thanks TWBM,

 

I can see this is going to be a rollercoaster of a journey !

 

Matt

[Graham Bowers]

I get 2.5 miles per litre from a 10 hp Honda 4 stroke on a 25 foot cruiser. As others have said, what you get will depend on the boat and outboard in question.

I have a 12 litre tank and carry another 15 litres in a well ventilated storage location. I just bought a 25 litre tank but haven't used it yet.

When on a big trip I use the internet to find petrol stations near the canal and mark them on my Nicholsons guides.

Graham

[Matt72]

Hey Graham

 

Thanks for that really useful info - do you mean the engine has a 12 litre tank, also the 15 litres - do you store it outside the boat or inside (sorry if that is a daft question)

 

THanks

Matt

[Tony Brooks]

Hey Graham

 

Thanks for that really useful info - do you mean the engine has a 12 litre tank, also the 15 litres - do you store it outside the boat or inside (sorry if that is a daft question)

 

THanks

Matt

 

 

Matt

 

It is NOT a daft question if you do not know the answer. You are doing things the right way in asking each question as it occurs to you and then clarifying the answer.

 

In my view all petrol tanks on a boat should be stored in a vented compartment which may be inside the boat with a cover or outside. The thing to do is to prevent petrol fumes getting into a bilge.

[Matt72]

Thanks Tony - unfortunately one answer tends to lead to more questions

 

What happens if petrol fumes get into the Bilge?

 

Matt

[mayalld]

Thanks Tony - unfortunately one answer tends to lead to more questions

 

What happens if petrol fumes get into the Bilge?

 

Matt

 

BOOM!!

[Tony Brooks]

Thanks Tony - unfortunately one answer tends to lead to more questions

 

What happens if petrol fumes get into the Bilge?

 

Matt

 

 

Once the concentration reaches a certain level one small spark or naked flame will give the result alluded to by Mayalld.

 

I know I get berated for saying this but I have seen the result of too many petrol boat fires to want to go down that route. Often the tank storage is fine with vents for fumes to fall overboard but then something happens whilst refilling the engine tank.

[Matt72]

Thanks both,

 

Off to have a look round David Mawby boats tomorrow so will probe him for more info - looking at previous posts on here he sounds helpful.

 

Matt

[Graham Bowers]

Petrol must be treated very carefully on a boat as its vapour is heavier than air so any vapour spillages will accumulate at a low point and then only needs a spark to ignite. There are plenty of places that sparks can come from - any electrical switch for example, even one on your bilge pump - or the commutator on any electrical motor.

My petrol tank is in a well at the rear of the boat that is "outside" and any vapour spills will drain overboard. There is enough space there for spare petrol.

There are those that say that petrol on a boat is too dangerous. I'd say that its an acceptably low risk if you obey "the rules". They are, keep the tank and spare petrol in an outside location that can not accumulate petrol vapour, and ALWAYS top up your petrol tank off the boat - even if its raining cats and dogs. I've recently bought a bigger (25L) fuel tank as on some river passages 12L is not really enough between mooring points and I don't want to get in to the situation where I can't top up off the boat.

And another thing. I think plastic fuel tanks / storage containers are porus and allow vapour to pass through, as I always get a petrol smell in my car if I have petrol in a plastic container in the boot - so even if a liquid spill does not occur, I suspect that vapour would accumulate at a low point if plastic containers are stored inside the boat.

Hope this helps

Graham

[AJLintern]

You could of course buy a diesel outboard... more expensive, but solves a lot of problems!

[Mikeonb4c]

You could of course buy a diesel outboard... more expensive, but solves a lot of problems!

 

Sorry to pop up out of nowhere, as a v. occasional visitor on here (I joined as I dream of one day cc'ing on a NB - fat chance probably!).

 

Is there not some simple device that could make the bilges of petrol fuelled boats safer? For example, a device using an air suction hose (situated at the best point(s) in the bilge) whose motor (not situated in the bilge!) switches on when petrol fumes are detected (they can do it for CO, why not for petrol?) in the blige.

[mayalld]

Sorry to pop up out of nowhere, as a v. occasional visitor on here (I joined as I dream of one day cc'ing on a NB - fat chance probably!).

 

Is there not some simple device that could make the bilges of petrol fuelled boats safer? For example, a device using an air suction hose (situated at the best point(s) in the bilge) whose motor (not situated in the bilge!) switches on when petrol fumes are detected (they can do it for CO, why not for petrol?) in the blige.

 

You mean a bilge blower?

 

Yes, such devices are available.

 

They are not, however, free, and at the cheapest end of the market, people who are spending a thousand pounds on a slightly tired outboard powered GRP boat are unlikely to buy safety devices that add a significant percentage to the cost of the boat.

[Mikeonb4c]

You mean a bilge blower?

 

Yes, such devices are available.

 

They are not, however, free, and at the cheapest end of the market, people who are spending a thousand pounds on a slightly tired outboard powered GRP boat are unlikely to buy safety devices that add a significant percentage to the cost of the boat.

 

I suspected as much. Mind you, a simple device using a manual switch should be easy and cheap to make, for those not too lazy.

[cereal tiller]

I suspected as much. Mind you, a simple device using a manual switch should be easy and cheap to make, for those not too lazy.

make sure is an IGNITION-PROOF type of blower /extractor.

[mayalld]

I suspected as much. Mind you, a simple device using a manual switch should be easy and cheap to make, for those not too lazy.

 

And even easier to get fatally wrong.

[Mikeonb4c]

make sure is an IGNITION-PROOF type of blower /extractor.

 

My thought was that by keeping the electrical components (motor, switch) outside the danger zone, you should be OK? Where might that be? Somewhere on deck and ventilated? Only the ducting would be in the danger area.

[Tony Brooks]

My thought was that by keeping the electrical components (motor, switch) outside the danger zone, you should be OK? Where might that be? Somewhere on deck and ventilated? Only the ducting would be in the danger area.

 

 

Except in typical bilge blowers the fan is on the end of the motor which, in turn, is mounted INSIDE the tube the fumes have to pass down. In days gone by (and now for all I know) being a DC motor they used brushes that are all most guaranteed to spark so the motor should be one designed for use in flammable atmospheres. I suppose a modern brushless DC motor and control that seems closely related to a stepper motor may not produce sparks.

[Mikeonb4c]

Except in typical bilge blowers the fan is on the end of the motor which, in turn, is mounted INSIDE the tube the fumes have to pass down. In days gone by (and now for all I know) being a DC motor they used brushes that are all most guaranteed to spark so the motor should be one designed for use in flammable atmospheres. I suppose a modern brushless DC motor and control that seems closely related to a stepper motor may not produce sparks.

 

and/or else keep the motor/switch out of the tube and use some kind of simple drive transfer to the fan unit in the tube?

[Tony Brooks]

and/or else keep the motor/switch out of the tube and use some kind of simple drive transfer to the fan unit in the tube?

 

 

That is not how typical bilge blowers are built. Even if you did manage to fabricate something how are you going to seal the apertures where the drive passes through the tube. I suppose it could be done with a shaft drive, special lip seals and a bevel gear but think of the cost. Then there is the question of what an insurance company might say about such a home made device handling explosive vapour.

[Matt72]

Getting away from Bilge blowers - I have had a look at a centre cockpit Viking 26 the other day and the petrol tank was in the aft cabin under one of the seats/bed in a compartement which had a vent slot to the outside. The petrol tank was metal not plastic. I was told it complied with all current safety etc.

 

Matt

[Tony Brooks]

Getting away from Bilge blowers - I have had a look at a centre cockpit Viking 26 the other day and the petrol tank was in the aft cabin under one of the seats/bed in a compartement which had a vent slot to the outside. The petrol tank was metal not plastic. I was told it complied with all current safety etc.

 

Matt

 

 

It probably would comply, although I would want a low level vent at the floor of the compartment, but that does not mean it is a good idea. Especially if its an outboard tank that has to have the fuel line removed to lift the tank out of the boat for filling.

 

Once you get into petrol boats there are a number of extra requirements in the Boat Safety Scheme.

[Matt72]

presumably though as long as you are careful and sensible the risk is low, otherwise there would not be many cruisers around

[Tony Brooks]

presumably though as long as you are careful and sensible the risk is low, otherwise there would not be many cruisers around

 

 

Each to their own, it is up to individuals to assess the risks in what they do and act accordingly.

 

Unless you spray diesel onto a very hot surface not much will happen apart from a smell. A little bit of spilt petrol will ignite with the merest spark and the fumes will build up in the bilge. This is why the type of carburettor and the extra safety equipment is defined in the BSS. Even so I have seen otherwise acceptable carburettors leaking petrol from the throttle spindle with the owners caring not a jot.

 

If my choice was a petrol boat or no boat then I would consider an outboard boat with the fuel tank(s)in vented lockers only accessible form outside the boat. I would rather have no boat than a petrol inboard and I am suppose to know how to look after them!

 

Not so long ago we had a case of a boater refuelling his petrol boat when his wife decided she needed a cup of tea. On went the gas and a very short while later BOOM. Luckily I think neither died but both were injured. That gas stove could just as easily be a passer's by cigarette.