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thanks for the info fnq. good one, yeah the mercruiser's attached to a big piece of fibreglass. interesting point about the full fuel tank aiding life, i always used to keep my tank full to have less air for condensation to form, this must have helped me with my fuel not seeming to go off.
I realise fuel loses some of its octane rating over time so your energy yeild will be slightly lower.
But can someone explain to me how old fuel can actually damage an outboard? and is it more dangerous for injected 4 strokes etc compaired to 2 strokes?
I have a carby 2 stroke and often leave it in my tank for 6months +(real pain to drain it) and I haven't had any issues at all.
Does the oil mixed in cause any issues aswell?
My understanding (very limmited) is that old fuel loses it's stability and becomes more volatile,the downside to this is that the fuel predetonates before the piston reaches TDC this in turn leaves the piston,driven by huge amounts of inertia,trying to compress an already expanding mass of gas,the end result is often parts failure..........but I could be wrong.
light volatiles ( things that go bang) in the fuel evaporate off and you are left with heavier oils , varnish and waxes
The heavier oils burn slow and hot with lots of deposits rather than than go bang in the combustion chamber
It can affect 2 and 4 strokes
Depends on how loaded the motor is and how well it is cooled and lubricated as to what damage happens
Hot slow burning oils burn holes in pistons and stems or seals off valves while screwing spark plugs. Deposits on cylinder walls and lean running can scuff piston skirts.
Waxes and varnishes can play havoc with hoses,carby bowl, needle and jets and with fresh fuel or "cleaner:" can be dislodged and become mobile and clog injectors or pre filters.
When motors are heavily loaded they basically can't get the heat out of them. With normal fuel the "bang"produces the HP and without it the motor labours and the natural reaction is to use higher throttle and hence more fuel and heat for same performance.
I have seen motors get that hot they have run in diesel mode where the heat ignights the incoming fuel and the motor can't be switched off even when you pull the plug leads
Have seen holes in pistons, screwed heads , scuffed bores, clogged exhaust ports and heaps of fuel delivery issues . Some fatal some not nut none are good.
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