• Rubbish in the carb?
• Faulty magneto or LT leads?
• Faulty HT lead?
• Faulty spark plug or gap too wide or electrodes oily?
• Spark plug not screwed in properly?

The spark plug is seated properly, the gap is too wide, and it is clean. I think the HT lead is ok, but have not had time to check. I will check the carb when I can, but am a bit run off my feet at the moment.

"the gap is too wide" The gap is not too wide*

I would say the low speed jets are plugged up a bit. either remove and clean the carburetor or run some carb cleaner with the fuel. These engines need to be run fast, the 2 cycle engines do not run well at low speed.

Also, check the fuel and see that it is fairly new, old fuel will gum up fuel lines, carburetor jets, and other items that are meant to be cleaned.

Al

I'll go with rubbish in the carb/s. For us Yanks, what's a RIB?

"Rigid Inflatable Boat"

The hull has a solid bottom with inflatable sides

What'll they think of next? Isn't that (Rigid Inflatable Boat) an oxymoron?

Sometimes referred to as a RHIB. Rigid Hull Inflatable Boat but it's pronounced 'rib'.

http://www.zodiaccz7.com/

Cheers!

The US military uses a lot of RIB's. They are almost unsinkable and can be stored in little space when deflated.

Are you using fresh fuel ?

Gas Mix Fuel setting on a boat for a long time is like desiel fuel takes a hot spark to burn it or a very warm motor.

Yes, the fuel is fresh, and yesterday after driving it for about 10 minutes, as I was driving in towards the jetty, and minimum rpm in forwards, it cut out again.

Oil mixed in with the gas or oil injection? Too Much oil???

Oil mixed with the petrol. There isn't too much oil, the other 4 2stroke engines are working perfectly. They are 2 25hp, 15hp, 10hp.

Different engines sometimes need different mix percentages.....I think that was what was implied.....

Oh ok. Thanks.

Check the vent on the fuel tank - might be blocked

The vent is ok on the fuel tank; there are 2 fuel tanks for it, and the problem occurs with both. Also, the problem is not in the fuel line.

Is the ignition timing adjustable?
Del

Next time it happens, quick like a bunny rabit pull a spark plug and tell us exactly how it looks. Is it wet? Black? Brown? white and chalky? Do this the instant it dies not after you have cussed it, restarted it, and then blown the carbon out of it. OK, you can cuss it first but don't restart it.

I had a similar problem with an older 9.9 Yamaha engine. Only at slow idle. I put the fuel tank up on the seat and the engine ran better at slow speed. I think it the suction the engine imparts on the incoming fuel line is insufficent. Maybe a pin hole leak in the line or a clamp not tight enough.

Good luck

That one might also indicate a partially-blocked fuel filter, making it run lean at low revolutions. It's worth checking, anyway, and renewing it is a simple thing to do.

Besides the carburetor there is a little lever attached to a linkage on the throttle, it selects between fixed speed (i.e. for a lawn mower) or adjustable throttle (for a go-kart).

Hopefully you just switched it unadvertently. Otherwise try cleaning your carb.

Yahlasit

I had a thought, what if I turned the idle speed up, so if it is going slightly faster, it may not stall.

On the Mercs I've worked on the ignition components move as the throttle is pushed until the max advance stop is reached. Check for frayed wires or wires broken under the insulation. -- JHF

And always remember 2 strokes are not happy unless you are wailing the snotskies out of them. They are not lazy 4 strokes that get cranky when you beat on them with the rpm stick.

If you have the older style mercury 40 hp 2 cylinder replace the stator if you have the newer 3 cylinder replace the CDI box

Knowing is half the battle