What's going on with my Mariner???

[Jack09]

OK, so I have a Mariner 40hp pull start. It's started giving me hassle lately by taking a while to start, if at all.

Fuel is fresh, brand new spark plugs, any water drained out of system, bled fuel out of it.

Once running its fine but it's been hit and miss in starting to say the least.

It was run with some old fuel in it at the start of the year so I binned it and replaced with fresh.

I had it running this morning and let it tick over for 10 minutes. Immediately re-started it first pull. Left it for 10 mins and it doesn't even sound like starting?

Any ideas?

One idea I had was that over the winter I re-sited the kill switch from the outboard to the console. This was extended using 1.5mm auto cable, soldered and heat shrunk. It all worked but wondering whether it could be the cause?

Any advice would be very welcome!!!

[paintman]

Needs compression, fuel & a spark at the right time.
When it doesn't start what's missing?

Before you altered the wiring did it ever have this problem? If it didn't then you might be right.

[telecast]

Does the problem only happen when hot and left for a while - or is it doing it when stone cold ?

[Jack09]

Both warm and cold.

It will start first pull immediately after being turned off. Seems to struggle if left a while

[Nos4r2]

Is it the old 40hp 2 stroke twin?

It's unlikely to be the kill switch.

[Jack09]

Looks like it is a 90's model. 40ML

[TmMorris]

If it runs perfectly well when hot and starts well when hot and all the issues are trying to start it cold then if it has a carb I'd be wondering if the butterfly is jammed or some other issue with the choke mechanism?

Easy enough to revert the wiring in the kill switch to double check. It doesn't seem likely but depending on how the current flows through the engine I guess the cabling could be causing a resistance that's impacting on the spark but it's hard to think it would.

[Nos4r2]

Well, if it's 90s it could be 2 or 3 cylinder. Wasn't ML one of the ex RNLI ones?

It won't be the kill switch if it's 90s. They make the circuit to stop the engine.

[spartacus]

I doubt it's the kill-switch. To rule that out when it fails to start, pull the HT leads, then one of the plugs and get someone to pull the starter while you ground one of the spark-plugs still connected to the HT lead to the engine block. If you get a spark you can rule that out. Work your way through all cylinders just to be sure.

Butterfly choke valve is a good call too. On the Tohatsu 2-stroke electric start - I've seen a sticky valve on the top cylinder cause grief when the solenoid actuates it, or not as the case may be. On a manual start engine - check that what's happening behind the airbox.

The sparks, especially if it's been running and up to temperature then anodes should be dry.

In the fuel side, no issue with the primer bulb and it goes hard? The internal diaphragm can fail and restrict flow. Easy to spot as the rubber flexibility goes hard and you may see some cracking on the outside too. Also check all fuel connectors for dislodged 'o' rings.

Only other area will be carbs themselves. Before dismantling, drain the fuel bowl on each just to be sure the fuel isn't contaminated.