Engine cutting out- throttle?

n428 · 04 April 2009, 11:50

Yam 50 4stroke- serviced about 30 hours ago.

A couple of times in the last outing the engine cut out as I went from low displacement speed and tried to accelerate (by pushing throttle). Engine cuts out quietly- no obvious noise. Fuel related issue? Plenty of fuel in tank and fuel bulb remains fairly firm?

Any ideas? Many thanks

Poly · 04 April 2009, 13:32

cuts out as in stalls (and needs the key to restart) or cuts out as in the revs drop away but it keeps running ?

neil.mccrirrick · 04 April 2009, 14:18

Timing problem, is the engine flooding, too much fuel?

n428 · 04 April 2009, 15:39

Sorry for confusion.

Cuts out totally. Need to use key to restart the engine.

Thanks for advice so far

Poly · 04 April 2009, 15:42

Quote:

Originally Posted by n428

Sorry for confusion.

Cuts out totally. Need to use key to restart the engine.

Thanks for advice so far

mmm.... thats what I thought you meant - I'm out then!

sam12345 · 04 April 2009, 16:26

Sounds like what i call a flat spot, but the engine cutting out completely is the weird thing.
The most common problems of throttle/power related problems are:
Fuel... stale, not getting through.
Carbs... gaskets gone, not syncd.
Coils gone

Does the engine literally just die, or does it pick up revs then die, or bubble a bit and die.

n428 · 04 April 2009, 16:45

Engine just dies. Doesnt happen every time I accelerate to get the boat on the plane- just intermitently.

biffer · 04 April 2009, 17:43

sounds like electric's' if it was fuel it would die more slowly, have a look at kill cord or wiring loom for anything loose

Nos4r2 · 04 April 2009, 18:18

Quote:

Originally Posted by biffer

sounds like electric's' if it was fuel it would die more slowly, have a look at kill cord or wiring loom for anything loose

I agree. Exactly which bit of electrics is a bit harder.

Either that or the end of your killcord is worn. I've had that happen-engine cuts out because it doesn't pull the killswitch out far enough.

alystra · 05 April 2009, 22:35

Isn't this just a case of flooding by opening the throttle too quickly from slow speed?

If I slam the throttle wide open from just above tickover in gear, my engine stops, instantly - but if I quickly ease the lever back it picks up again or the spinning prop starts it and we carry on. If I'm not quick I have to use the key. After 2000 RPM the problem goes away.

This behaviour is exactly similar to that of my first few cars. Basically the throttle pumps extra fuel into the engine and puts out the fire. Push the accelerator down gradually to get maximum acceleration. That's what we were taught, and it worked. Stamp on the thing and the engine coughed and spluttered. That was with just two carbs. My Merc has four.

Of course, if your engine is a modern fuel injected, computerised one then you may have to pay someone a fortune to plug in a lap top and come to the same conclusion.

9D280 · 06 April 2009, 10:23

Alternatively if your idle mix is a touch on the lean side, it just doesn't have enough fuel to get you over the hump, so to speak.

Easy test for that - as you open up, prod the choke. If it roars into life, it's too lean. If it coughs & dies, you may be too rich as Alystra says. A simple minute turn of an adjuster screw(s) on the carb(s) will cure it.

outboardtech · 06 April 2009, 16:16

Guys , firstly before you start going for it and adjusting mixture screws and timing etc etc you NEED TO KNOW if this is a FUEL problem OR an IGNITION problem . I agree a fuel problem the engine will slowly gradually surge and loose RPM and then cut out , by the sounds of things here this OUTBOARD is cutting out immediatly as someone has pulled the kill cord . You really need to get it into someone who can hook up the computer to it ( i can do that ) and simply do a ignition drop test on each cylinder and diagnose the problem properly before seriously causing more problems . Also its already been said it could be a fault in the stop circuit from the control box and the wiring is shorting out taking that wire to an earth cutting the ignition spark . Is this engine E.F.I or a Carb Model ? cheers Baz

biffer · 06 April 2009, 17:55

Quote:

Originally Posted by biffer

sounds like electric's' if it was fuel it would die more slowly, have a look at kill cord or wiring loom for anything loose

i'll post it again just i case you missed it, trust me!!!!

Bigmuz7 · 06 April 2009, 20:32

Quote:

Originally Posted by biffer

i'll post it again just i case you missed it, trust me!!!!

frustrating as hell sometimes .. innit bif ? Chill dude

biffer · 07 April 2009, 07:34

mmmmm!

m chappelow · 07 April 2009, 08:00

transition from slow running jet over to main jet .

n428 · 19 April 2009, 15:30

Having used the boat last week I've got more of an idea of the problem.

When accelerating hard the engine splutters slightly before cutting out- when I noticed it starting to splutter I throttled back and all was well.

Does this info help- makes me thinking its more fuel related than electric.

Thanks for all your help