The honest answer is it depends Frank.

Some fuel may be "shandied" illicitly by servo station owners with other combustible liquids like toluene that are cheaper to buy than petrol.

Some blends may have a % alcohol even! Grain, sugar, ethanol methanol etc etc.

Alcohol and or toluene etc may actually trap water moisture from the surrounding air, so aren't good to be left in fuel tanks and also might deteriorate some rubber fuel system componenets over extende d periods!

The thing is - your right in that fuel goes off (stale) with time - but if you have underfloor built in fuel tanks, then leaving them empty thru winter is worse. The expansion / contaraction of moist winter air every day and night brings in new moisture each day which condenses out of the air on the inside of the tank each night and over a long period this water adds up to quite a lot.

Such water os damn hard to get OUT of a below decks fuel tank!

If the tanks left full of fuel over winter - theres no room for moist air!

So - drain the fuel and replace it at the beginning of next season,(putting it mixed 50 / 50 with fresh petrol thru your lawnmower or wifes car!)..and fill her up with fresh gogo juice at the first outing come summer!

As for winterising the outboard thats a whole nuther subject!

Cheers!

Thanks for your reply Flywest. Perhaps when you have time you could post something to do with winterising outboards as I guess quite a few people are going to be doing that in the next month or so.

I've always just hosed down the whole boat, trailer and winch with fresh water, flushed to engine for 10 minutes, removed the cowling and sprayed WD40 over the engine, put the cowling back on, and that's it.

Each week in winter I manually turn the engine block from side to side several times to try and prevent the steering from siezing up and every month, I put the muffs on and run it for 5 minutes or so.

cheers

Frank

I winterise my boat by putting on an extra jumper then heading to the nearest boat ramp for a fish.

Excellent topic though Frank, even with the best intentions my boat has sat there for a couple of months occaissionally and it would be good to know some handy hints about maintainance in those circumstances.

What about your batteries? Do you disconnect or leave on a trickle charge? I would suggest disconnect completely.

Would love to do the extra jumper bit!

I disconnect the batteries completely and hold my breath when I try to start up each month. I also remove everything from the boat so there is nothing that can get pinched should someone jump the fence for a quick look.

Furthur to Flywest's post, my boat mechanic suggests if the fuel is not mixed eg engine is oil injected, it is safe enough to leave in and can be of benefit as outlined by FW. Leaving an outboard pre - mix in the tank can be a problem as the petrol and oil seperate over time so you won't necessarily have the right fuel:oil ratio when you next start up.

If you have an oil injected engine, don't disconnect the fuel line and run her dry as part of the flushing out process because the oil keeps pumping into the engine even as the fuel runs out. Everthing gets clogged up with oil and it won't start next time - I know - I've done it! Was told this was the correct process at a TL3 course but the guy didn't distinguish between oil injected OB's and others.
Bugger!

I am certainly no mechanic. But I think a trickle charger is a gentle top up machine that you can put your batteries on. It converts 240 volts to 12 volts and tops up your batteries.

Just don;t make the same mistake as I did the day before a local fishing comp. I put a solar powered trickle charger on in the morning but left it connected overnight before the comp. Unfortunately when the sun goes down, unless you have a diode/converter/valve thingy majiggy conected the charge simply trickles back out. So I was left with a completely drained battery the day of the comp. (Doh!)

My engine is oil injected too so I try and leave the fuel tank full through winter. In summer however you can lose a lot of fuel through vapor leaking through the overflow as the fuel expands due to heat.
In summer I fill up the morning of the fishing trip so the tank is half empty most days. I'm about to convert to the Winter method of filling back up on the way home so it sits there full at all times.

Unfortunately I am in no position to give advise from a mechanical perspective. I think Flywest would be able to give us a better response. I am sure what I am doing is totally wrong, but I have never had a drama with fuel other than it leaking all over the place when it's hot and I have a full tank.

Is'nt there some kind of water filter on most engines these days?

I think I am the one that needs the advice just as much as you do Spooled.

Re Andy Mac's comment about most engines having most engines having a water filter these days; can any of us average punters keep up with technological developments in OB's these days?

Can a bloke who self - serviced his 1990's OB service his year 2000 onward OB - probably not! Conditions of most engine guarentees would probably stop us from even trying. Who would risk a null and void guarentee on a $10,000 engine to perform a self - service? Not me!

Winterising is something the Yanks in cold (snow) climbs do annualy.
Its a whole rigormorole they go thru, getting all the fluid out especially water for example that might sit in a thru prop exhaust hub (and parts of the lower unit) with the OB tilted up!

When this water freezes it expands and can crack (destroy) your lower unit! Not a problem for you guys near the coast in Perth, bit different where I lived in Nannup and we had minus 4 degree mornings etc!

The yanks also spray "fogging oil" all thru their engines prior to shutting them down for winter - they do this by spraying it into the carby until it eventually bogs the engine down until it won't run!

This keeps the cylinder walls rings and bearings etc etc all coated in a heavey (Bar & Chain oil / HP90) type coating to prevent rust!

Get this - many of them have their whole boat Plastic cling film wrapped for the winter (just like you see farmers wrap bales of hay here now!).

When they de winterise they have to burn all that heavey oil out again and it leaves heaps of carbon behind on piston crowns (spark plugs) etc so they have a spray decarbon stuff (seafoam) that they again spray down the throat of the carby once they have started and burnt all the heavy fogging oil out...making great clouds of smoke everywhere!!

Anyway - like I said - what the yanks do and what we need to do are two different things!

Frank I deliberately didn't type anything about running the carby bowl dry - as a result of your experience with the TL3 course and oil injection systems!

The advice about TCW3 oil separating out is also true - add your oil before your first trip out in summer - just top the tank with fuel for winter and if that fuel goes stale shandy it into the wifes car 50 50 with new stuff!

Why the wifes car?
OK. Lets face it. REAL Men drive diesels! - deep 'Tim th' tool man", arrhh arrhh arrhh sound! ;o)

If you want to you can pull the plugs for winter, and spray CRC direct into the cylinders thru the plug hole! Plug the holes with rag (or re insert the plugs loose, just a turn or so and don't connect the plug leads - this way you can turn the engine over by hand on the flywheel once a month and add a little more crc - this tends to stop the rings sitting in one place all winter and electrolysis acids etc forming little permanent grooves around the cylinder wall where the pistons rings sat for 6 months!

Disconnect the battery / s and take it/them out of the boat altogether! Leave it on a trickle charger, topped off, and leave it sitting on a plank of wood, not a concrete floor!

No idea about the tropics - never lived there...imagine the locals would have evolved a system that works by now - probably what they do in Floridah - fish every day! ;o)

Cheers!

Correct me if i'm wrong but if you empty out the fuel tanks doesnt this increase the risk of water condensing in the tank and causing a drama.