Two stroke engine query...

Rappey69

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I have a twin cylinder mariner 8hp outboard, 2 stroke and barely 20 hrs run time..
Leave it for weeks and it starts up straight away every time..
Turn it off, start it again and no problem..
Leave it for around 6 hrs and it refuses to fire, taking around 15 mins of turning over before it will finally run, then runs fine..
Put it away, days or weeks later will always start first pull ??
Any suggestions as to what the 6 hrs later problem could be ?
 

Warrior

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I've done a lot with 2 stroke engines over the years, mainly racing motorcycle engines, is it injected or carb?

With such low hours you should be able to rule out wear on items such as crank seals or piston rings, so i'd be suspicious of the ignition.

But first of all the next time it refuses to fire whip out the plugs and drop a small amount of fuel into the cylinders, just about a couple of teaspoons, then see if it fires, if it does its a fuel issue which could be a result of a damaged seal due to incorrect assembly at the factory (it happens) or a vacuum forming in the fuel supply (i'm not familiar with marine applications do they have fuel pumps or are they gravity fed?)

If a splash of fuel down the plug holes doesn't make it fire get the ignition system checked out as sometimes the system can retain some residual heat and cause problems if there are already some faulty components in the system.

Try the above and get back to us.
 

Ultymate

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Firstly there's a Mercury Mariner and also a Yamaha Mariner but after a quick google I think they both have carbs and these are usually a Walbro or Tillotson carb or a similar clone and these usually have a diaphragm and twin valve pump built into the carb. Your fault sounds to me like the engines heat soaking the carb after stopping and vaporizing the fuel and causing a vapor lock and hence the no start until fully cooled down. I wouldn't rule out ignition but I would suspect the carb/pump first
 
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Rappey69

Rappey69

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Forgot to say its a carb engine, and the choke? lever presses on a pump on the carb to pump some fuel..
Did try squirting some easy start into it but still nothing, so that sort of points to electrical, but with such low hrs and running faultlessly when running?
I know i should whip out the plug when struggling to restart, but when its on the back of a boat its not the easiest thing to do..
They have a sort of fuel pump on them as the remote fuel tank sits lower than the engine.

Another absolute pain in the butt is that it has the gears on the throttle handle, so impossible to start with a few rpm,s.. It can only be started on tickover..
It must be mariner/ mercury as if yamaha it would not be such a pile of cr*p ! (my less than 100 hrs mariner 90 blew up last summer)..
My ancinet yamaha before that went on and on and on and ....
 

Warrior

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If it doesn't fire on easy start then i'm assuming it must be an ignition fault, a two stroke only needs compression, a spark at the right time, and fuel if they are all in place it will at least fire and attempt to run.

Things that have caught me out in the past have been silly little things like condensation in ignition kill switches, does it have one? if it does is it positioned where it could get warm and then cool after being around water? can you bypass it and try it?

With such low hours is it still under warranty?

I've never dabbled with marine engines but have spent a lot of time on Honda and Yamaha racing two strokes.
 
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Rappey69

Rappey69

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It does have a kill switch but marine units are usually well waterproofed.
the engine is a fair few years old, just hardly ever used until i bought it...
guess im just going to have to take some tools out with me and do some checks when it refuses to restart after being left for the day..
some good advice though guys..
 

Warrior

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The next time it faults try these :-

Bypass the kill switch.
Pull the plug(s) and check the spark

If this doesn't throw up anything obvious find the coil and stator resistances/values for the ignition and check them with a multi meter, or send the entire ignition to a specialist and get them to check it over.
 
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Rappey69

Rappey69

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Used the engine saturday. Its a mercury, not a mariner :Oops:
Has the gears on the tiller, or hand throttle so as i think i mentioned, not able to add some throttle when starting..
This time i removed the engine cover, manually pushed the throttle linkage whilst pulling engine over and it fired up straight away !
What a stupid design !
 

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