Seagull Outboard

Joyce_boat · #1 01-08-2005, 11:11 AM

I am certain that many of you have a seagull outboard motor as a "back up"
motor. I have been told that I cannot use unleaded petrol in them apparently it wrecks them.As 4 star petrol is now non existant what grade of petrol can I use? I would appreciate any advice.
Many thanks,
Joyce_boat

welsh wizzard · #2 01-08-2005, 12:46 PM

if you really need to use leaded petrol get yourself off to a local car shop. you can buy a leaded subtitute which you mix in when you fill up next.
as for the not being able to use it. if this motor is only a few years old there should be no reason you cant use unleaded as long as you change the ignition timing.
Lead in petrol does two things. Firstly it increases the fuel's octane rating making it less prone to 'knock' or 'pinking', this is when the fuel in the engine burns in an uncontrolled manner, potentially causing damage to the engine. Secondly it protects the engine's exhaust valve seats from wear. motors which are designed to run on unleaded fuel have very hard valve seats which resist wear.

hope this helps a little

ChrisP · #3 01-08-2005, 08:30 PM

Seaulls will run OK on unleaded but make sure the fuel is fresh. They don't like stale fuel or stuff that has been mixed for too long.

GrassHopper · #4 01-08-2005, 10:36 PM

Quote:

Originally Posted by ChrisP

Seaulls will run OK on unleaded but make sure the fuel is fresh. They don't like stale fuel or stuff that has been mixed for too long.

so what sort of engine are they 2/stroke then?

ChrisP · #5 01-09-2005, 02:09 PM

Very basic 2 stroke engine, dead simple engineerins so not much to go wrong, fresh fuel and a new plug each year and they will run and run. some are 25-1 mix and others 12.5-1 mix.

I think they were designed as a throw away engine for the army about the time of WW2, some of those engines are still running today.

GrassHopper · #6 01-09-2005, 03:27 PM

then it should not matter if you run it on unleaded as there are no vales on a 2 stroke

ChrisP · #7 01-09-2005, 04:43 PM

Spot on about the valves but some makes do requre retuning as they suffer from pre ignition (pinking)with unleaded that can lead to engine damage.

Seagulls are not highly tuned so not affected by the different octane rating of unleaded. Unleaded fuel does not have as long a shelf life as the old leaded hence the advice about fresh fuel as it is mixed with such a high proportion of oil, it needs the volatile fractions for ignition.

welsh wizzard · #8 01-17-2005, 05:11 PM

Quote:

Originally Posted by GrassHopper

then it should not matter if you run it on unleaded as there are no vales on a 2 stroke

there are valves on a 2 stroke. they just work a little differently to a 4 stroke engine

GrassHopper · #9 01-17-2005, 07:06 PM

yes ok but not in the nomal way as in a four stroke motor so i take it you are now talking reed valves or rotary ones like on a kh 125?

i cant see unlead being a real problem all it will do is lower the octane rating of the petrol mix

flash · #10 01-26-2005, 09:17 AM

my dad gave me his seagull its around a 1950ish model and its only had about 3 spark plugs in its life it was given to him by the guy who had it from new it has only let us down 1 time it needed the jet ( not sure if thats correct as im not a mechanic) cleaned iv got all the original books and brochures and we just run 2 stroke the new type of leaded fuel im not sure if its the same as you guys use and its great for chugging away on our down under water ways

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