Why won’t my outboard start ?

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FairMaid

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My Mariner 3.5 4 stroke outboard won’t start - It’s just a couple of years old and has been working fine - OK it has been in the garage all winter and normally needs more than a couple of pulls for its first start of the season (in a water filled dustbin) - it has fuel, had spark plug out and cleaned and kill cord attached (OK not true - I left it on the boat - but bungy cord wound round keeps the kill button far enough out - and this has worked OK in the past). It turns over but is not firing at all. What should I try ?
 
FairMaid said:
My Mariner 3.5 4 stroke outboard won’t start - It’s just a couple of years old and has been working fine - OK it has been in the garage all winter and normally needs more than a couple of pulls for its first start of the season (in a water filled dustbin) - it has fuel, had spark plug out and cleaned and kill cord attached (OK not true - I left it on the boat - but bungy cord wound round keeps the kill button far enough out - and this has worked OK in the past). It turns over but is not firing at all. What should I try ?
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  • Check spark. It should be possible to get a good powerful spark which will jump good 10mm.
  • Fresh fuel if not already fresh.
  • Check fuel flow to carb
  • Check compression
  • Try Easy Start
  • Clean carb
 
After attempting to start it, take the plug out and examine it. If it is dry, then fuel is probably not getting through. If wet, then the spark is not good enough. My guess would be that the carb jets are bunged up with fuel deposits.
 
Fuel goes off rather quickly, especially premixed. Sniff the tank. Smells foul? Found your problem. If the tank was dry you might try cleaning carb (needle drys out and sticks) and fuel filter and check fuel is flowing. All good? Can only be the spark or compression.

/luck ... mines a seagull so I feel your pain!
 
I'm not suggesting that you would be so silly, but my Honda refused to start after I filled it up with diesel. :shame:
 
Thanks for the replies - it’s fuel (spark OK but dry) - have taken fuel tank off to look at carb - but I’m worried about taking carb off and dismantling - the user manual doesn’t cover the carb and online YouTube video I found doesn’t get me enthusiastic about tackling it - will I need new seals/gaskets if I dismantle ? - my only experience is of 2 stroke motor bike a very long time ago and lawn mowers - is it a job for the marina workshop or should I just not be a wimp and press on ?
 
Small Honda carbs are pretty bomb proof in terms of taking them to bits and reassembling them. If you’re worried about it, remove the carb and clean the outside then do the dismantling slowly and photograph each stage so you can see which bit goes where. I use a tea tray with a lint free cloth on it to do the job on and lay out the bits with screws next to the it they retain and so on. You shouldn’t need to replace any seals or gaskets as you go, just take it slowly and gently prize things apart rather than brute force if you encounter any resistance.
Search on line for a workshop manual or look for an exploded parts diagram so you can see what goes where before you take it apart.
 
I learned the hard way, but if you turn off the fuel and allow the engine to stop by running out of fuel. When you go to use it again after a period of time it starts first time. The trick is to empty the carburettor when you are going to not use the engine for a while. This is every important with two strokes.
 
Seven Spades said:
I learned the hard way, but if you turn off the fuel and allow the engine to stop by running out of fuel. When you go to use it again after a period of time it starts first time. The trick is to empty the carburettor when you are going to not use the engine for a while. This is every important with two strokes.
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+1 to that, though my Tohatsu 3.5 needs a dozen pulls to start the first time, possibly because I don't wait long enough for the fuel to find its way from the tank to the carburettor.

IIRC, a Mariner 3.5 is a badge engineered Tohatsu. The service manual including exhaustive (and exhausting) detail on the fuel system can be downloaded here as a PDF you can print out
 
Dan Tribe said:
I'm not suggesting that you would be so silly, but my Honda refused to start after I filled it up with diesel. :shame:
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I managed that too but didnt determine problem. Then took my spare outboard down to boat and it ran fine so I topped it up from same can with of course the same result. Fortunately when service engineer identified to problem on one I flushed out the second. I now have can of petrol diesel mix hidden behind shed for starting bonfires:eek:
 
Problem solved - by the boar yard - I had left fuel in the carb and it had turned into a jelly sludge - I know I should have drained it but hadn’t had that problem before
 
There is a game to be played here in which the price of failure can be quite high.

Outboards will run for quite a while after the fuel line has been disconnected so are you brave enough to cut the fuel some time before you get to your berth/mooring/pontoon and glide in just as the motor dies?

Hugely satisfying when you get it right.
 
wombat88 said:
There is a game to be played here in which the price of failure can be quite high.

Outboards will run for quite a while after the fuel line has been disconnected so are you brave enough to cut the fuel some time before you get to your berth/mooring/pontoon and glide in just as the motor dies?

Hugely satisfying when you get it right.
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Hugely embarrassing when you don't. :D
 
wombat88 said:
There is a game to be played here in which the price of failure can be quite high.

Outboards will run for quite a while after the fuel line has been disconnected so are you brave enough to cut the fuel some time before you get to your berth/mooring/pontoon and glide in just as the motor dies?

Hugely satisfying when you get it right.
Click to expand...

It was standard practice with a Seagull; One quickly got the 'knack';
 
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