Old petrol in inboard tank

[Matt252]

Morning all,

I’m after some advice please:

I’ve got a 2018 Brig Navigator 570 with a 100hp 4 stroke Suzuki.

The boat has an inboard tank, and after a winter of not using the boat, combined with lockdown some of the fuel in the tank is getting pretty old. Some is exactly a year old, when I filled the tank for a holiday last year. Some is less old as I topped up over last summer. So it’s a mix.

The engine starts and runs fine, but am I risking damaged or breakdown if I take the boat out in the estuary - as I hope to on Friday?

Really appreciate some advice please ?

Cheers

Matt

[beamishken]

Originally Posted by Matt252

Morning all,

I’m after some advice please:

I’ve got a 2018 Brig Navigator 570 with a 100hp 4 stroke Suzuki.

The boat has an inboard tank, and after a winter of not using the boat, combined with lockdown some of the fuel in the tank is getting pretty old. Some is exactly a year old, when I filled the tank for a holiday last year. Some is less old as I topped up over last summer. So it’s a mix.

The engine starts and runs fine, but am I risking damaged or breakdown if I take the boat out in the estuary - as I hope to on Friday?

Really appreciate some advice please ?

Cheers

Matt

Your fuel will be fine as long as you have decent filters to catch any contaminants. As fuel ages a little of the more volatile compounds that aid starting evaporate off however this is very slight & if your engine is starting & running fine then your ok to use it.
If you are concerned at all then top off with some fresh fuel.
Most running problems after layup are caused by fuel left in carbs evaporating and leaving a residue which can block jets. Again if the engine is running fine they your all good.
There are a lot of urban myths about old fuel which simply arent true

[jeffstevens763@g]

get some fuel set it reconditions the fuel and as BK says top up with clean fuel

[Fender]

Used my boat last week for the first time ( Covid and all that ), about 8 months since last in the water and she ran lovely - added some fresh petrol at the first fuel berth we passed just to be sure but probably didn't need to bother. Just enjoy

[paulbrown22]

Agreed - I typically just top up with fresh fuel, and assuming it's running happily on a hose, no signs of missing cylinders, rough running, etc, get it launched and start burning through the tank! Once it's launched and up to temperature, you can do a quick test just to check it operates okay throughout the rev range, and doesn't struggle for power.

On my carb engines if I know I'm not using it for a long time I try to remember to disconnect the fuel lines and run the carb dry, but obviously don't always do that, and haven't yet had a problem with our various petrol outboards.

[gtflash]

Do some of the fuel treatments promote the water seperatuon in fuel?

[jeffstevens763@g]

Originally Posted by gtflash

Do some of the fuel treatments promote the water seperatuon in fuel?

fuel set breaks it down so it burns

[Sutty]

Just to play devils advocate how would you get the fuel out if you were persuaded it was duff

[Allye]

Siphon it quite easily or cheap inline 12v pump.

[mikehhogg]

good quality fuel if treated before storage has a shelf life up to a year, untreated about half that time and poor quality fuel like the crap we have here in Ireland that is blended with animal fats to fulfil biofuel requirements about a month.I wouldn't have thought that it could cause any damage to an outboard engine only run poorly but after a quick google search the solids content can increase with age and cause premature wear to fuel pumps and injectors.

[Sutty]

Originally Posted by Allye

Siphon it quite easily or cheap inline 12v pump.

Don’t think it would be that easy, to siphon it out the output end has to be lower than the input end so not much room to place the containers to collect it, you have also got to dismantle the fuel input from the engine. My tank holds 70 gallons at siphon speed that would take literally all day and then you need lots of containers. Same problems with inline fuel Pump plus the danger of electric and petrol. So much easier to turn the key and use it. Just started one of my motorbikes up with three year old fuel and no problem. Fuel going off a bit of a myth if kept in sealed tank or system for a reasonable amount of time - several years.

[Allye]

Originally Posted by Sutty

Don’t think it would be that easy, to siphon it out the output end has to be lower than the input end so not much room to place the containers to collect it, you have also got to dismantle the fuel input from the engine. My tank holds 70 gallons at siphon speed that would take literally all day and then you need lots of containers. Same problems with inline fuel Pump plus the danger of electric and petrol. So much easier to turn the key and use it. Just started one of my motorbikes up with three year old fuel and no problem. Fuel going off a bit of a myth if kept in sealed tank or system for a reasonable amount of time - several years.

Yes that’s generally how siphoning works, if you’re silly enough to leave 70 gallons in the tank for a year you deserve the misery of it taking all day. Why would you ask for advice then “poo poo” literally the only ways of removal, then go on to say you’ll try and turn the key anyway?

Dangers of electric and petrol?! So every single modern car driving around is at great danger with there electric fuel pumps are they? I’ve siphoned and used electric fuel pumps to empty large 4x4 tanks numerous times (scrap cars I’m not a pikey!)

[Poly]

Originally Posted by Allye

Dangers of electric and petrol?! So every single modern car driving around is at great danger with there electric fuel pumps are they?

Well not quite the same the battery, electrical and fuel systems in a car are carefully designed to avoid unnecessary sparks, have a closed fuel system and for all components to by compatible with the fuel involved. Using a pump to drain a boat tank more often than not probably isn’t as well engineered - loose connections, pumps not designed for use with petrol, flexible hoses not clamped in place and feeding into open tanks is a real risk, more so if it’s afloat at the time and waves are moving everything around and I think it is appropriate to highlight that to people who may not have your experience:

I’ve siphoned and used electric fuel pumps to empty large 4x4 tanks numerous times (scrap cars I’m not a pikey!)

of course the fact you haven’t died in a fireball yet doesn’t mean you were actually totally safe and not just lucky!

Plenty of diesel transfer pumps around, even hand drill attachments, cheap which are not intended to be used with fuel.

[Poly]

Originally Posted by Sutty

Don’t think it would be that easy, to siphon it out the output end has to be lower than the input end so not much room to place the containers to collect it, you have also got to dismantle the fuel input from the engine.

You don’t need to dismantle the fuel input - you can suck it back out through the filler pipe. If the boats on a trailer you can easily get a good height difference. Of course if you are going to disconnect the fuel outlet from the tank/inlet to engine and it’s on a trailer you can feed your hose out an elephant trunk or bung and let gravity do its work. What are you going to do with 70 gals of dodgy fuel though? You’ll need a lot of Jerry cans and some way either to dispose of it or use it that is less delicate than your engine - might be easier to pay a fuel conditioning / polishing specialist to do it for you, if you find yourself in the unlikely situation of really needing to drain 70Gal from a tank.


With old fuel my approach has been 1. Top off the tank with premium 98 Ron fuel. 2. Have a small portable tank of fresh fuel with you.

And from bitter experience (although it wasn’t the age of the fuel) know how to change your fuel filters and have spares with you.

[Pikey Dave]

Originally Posted by Poly

You don’t need to dismantle the fuel input - you can suck it back out through the filler pipe. If the boats on a trailer you can easily get a good height difference. Of course if you are going to disconnect the fuel outlet from the tank/inlet to engine and it’s on a trailer you can feed your hose out an elephant trunk or bung and let gravity do its work. What are you going to do with 70 gals of dodgy fuel though? You’ll need a lot of Jerry cans and some way either to dispose of it or use it that is less delicate than your engine - might be easier to pay a fuel conditioning / polishing specialist to do it for you, if you find yourself in the unlikely situation of really needing to drain 70Gal from a tank.


With old fuel my approach has been 1. Top off the tank with premium 98 Ron fuel. 2. Have a small portable tank of fresh fuel with you.

And from bitter experience (although it wasn’t the age of the fuel) know how to change your fuel filters and have spares with you.

A 3/4 jiggle syphon (about £15) will shift 20litres in a couple of minutes [emoji106]

[Allye]

Originally Posted by Poly

Well not quite the same the battery, electrical and fuel systems in a car are carefully designed to avoid unnecessary sparks, have a closed fuel system and for all components to by compatible with the fuel involved. Using a pump to drain a boat tank more often than not probably isn’t as well engineered - loose connections, pumps not designed for use with petrol, flexible hoses not clamped in place and feeding into open tanks is a real risk, more so if it’s afloat at the time and waves are moving everything around and I think it is appropriate to highlight that to people who may not have your experience:

of course the fact you haven’t died in a fireball yet doesn’t mean you were actually totally safe and not just lucky!

Plenty of diesel transfer pumps around, even hand drill attachments, cheap which are not intended to be used with fuel.

Make sure you wear your cotton wool, hard hat and a harness.

[Matt252]

Well, thanks for all the replies - took the Brig out in Salcombe, added some fresh petrol (~20 litres) and had a day motoring about no problems. Really helpful guidanace tho, I was concerned as it’s a new engine and didn’t want to damage it, so thanks for that

Incidentally, before all that I tried the symphony method, couldn’t find a way to get a tube to reach the fuel tank, it’s around 4m away from the filler point and a very flat angle. Anyway, hopefully not needed now.

Cheers all!

Matt

[mikehhogg]

coincidentally with eased lockdown restrictions we have received a host of petrol issue items from outboards to lawnmowers to motorbikes. After three months of non use we found what appears to be sand in the carb bowls left behind by evaporated fuel,we also noticed that ultrasonic cleaning does not shift this residue,a third observation was a fuel tank so shiny it could be mistaken for being polished,this we are putting down to additives in the fuel.My advise to anyone using any petrol powered device is to switch off fuel supply and let it run out until engine coughs or dies, and leave fuel no longer that three months,mixing with fresh fuel although helps is not healthy for expensive outboards.I am speaking for the fuel quality we have here in Ireland,its shite.

[jeffstevens763@g]

Originally Posted by Matt252

Well, thanks for all the replies - took the Brig out in Salcombe, added some fresh petrol (~20 litres) and had a day motoring about no problems. Really helpful guidanace tho, I was concerned as it’s a new engine and didn’t want to damage it, so thanks for that

Incidentally, before all that I tried the symphony method, couldn’t find a way to get a tube to reach the fuel tank, it’s around 4m away from the filler point and a very flat angle. Anyway, hopefully not needed now.

Cheers all!

Matt

when i did mine i extended the outlet from the fuel/water seperator down into a spare tank primed the bulb and syphoned that way takes a while

[Nasher]

I've got to do mine soon.

I reckon I've got @50-60l of 3yr old fuel in my inboard tank.
At least the filler neck is almost vertical straight down into the tank at it's deepest point.

My old DT200EFI liked clean fuel, but moving on(up) to a 225 Optimax I'm not taking any chances.

It would be nice to find a way to flush the tank out without picking the boat up, sloshing it about and tipping it out!

I'm actually thinking about getting one of the mis-fuelling specialists to come and pump it out, as pumping it out is one thing, disposing of it is another matter.
I don't want it hanging around for months whilst I put a couple of litres at a time into Lady Nashers Mini, and it's going nowhere near the newly cleaned out carbs on my old Ducati which already doesn't like modern fuel at the best of times.

Nasher.