Engine dies at WOT

Tom465 · 10 August 2012, 20:27

Hi,

Went out yesterday and to start off with, I drove over some submerged netting and wrapped up and stalled the engine.

Managed to cut it free and thought id anchor up stop for some lunch.

When I came to set off agiain the engine was fine, but then when I went to WOT the engine would start like chugging and slowly the revs would drop and it would stall.

It would also stall if it accelerated hard. It works fine if I slowly accelerate to 3/4 throttle.

Im thinking its fuel related ? Any help would be great... Thanks

Jamesg514 · 10 August 2012, 20:48

I had this on my e-Tec it turned.out to be the fuel tank pickup

Bigmuz7 · 10 August 2012, 21:03

Or the dreaded air vent on the top of the tank .. was it open ?

John Kennett · 10 August 2012, 21:21

A dodgy primer bulb is another potential culprit

jambo · 10 August 2012, 22:38

Could also be a dodgy diaphragm or blocked jet. Dirty fuel maybe.

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lockieboi · 11 August 2012, 08:03

Quote:

Originally Posted by Bigmuz7

Or the dreaded air vent on the top of the tank .. was it open ?

I'm guilty of this

Trevor G · 11 August 2012, 11:30

Quote:

Originally Posted by Tom465

It would also stall if it accelerated hard. It works fine if I slowly accelerate to 3/4 throttle.

Im thinking its fuel related ? Any help would be great... Thanks

We had same problem a few weeks ago on our Suzuki DT75 - turned out to be the gear linkage squashing the fuel line in the engine housing (fuel line not in it's proper clips).
Only happened at WOT as this pushed the linkage just a little bit harder against the fuel line.

Tom465 · 11 August 2012, 15:16

thanks for all the suggestions

Spent the morning following up all your comments.

Pick up pipe was good and unblocked
Yes the air vent was open
Bulb was working good
All fuel lines are fee and not cough up or blocked
Fuel Filter is clean
Plugs are also good.

My engine is a 30hp Yamaha auto lube.

I did use some old fuel the time before I went out. It was 200:1 oil mix so I thought it would be ok ?

This time I went out it was clean fresh fuel.

When it is idling it would now missfire and stall.

jyasaki · 11 August 2012, 17:09

200:1 sounds pretty lean for a 2-stroke. What's your spec say -100:1? 50:1? Not enough oil is a recipe for disaster.

Dump the suspect fuel, fill with fresh (and correctly mixed) fuel, and see what happens.

If you suspect a fuel pump, try pumping the primer bulb while running. If it corrects the misfire, then it's definitely a fuel delivery problem. Fuel filter, fuel pump, or clogged line, most likely.

jky

Davie · 11 August 2012, 17:37

Sounds like fuel but as the problem started when you got fanned up I would check your bush has not slipped further up the propshaft and your propeller is not eating your gearcase.

Hightower · 13 August 2012, 00:32

I though Yam 2 strokes are 50:1 (someone will be along to confirm I expect), I hope you haven't got piston pickup though lack of lube. I thought that early signs of this is for thinks to start seizing up when running hard (Hot) the piston expands and gets tight in the bore.

Short of that, the Primer bulb is prime (no pun intended) candidate, even if it appears to work normally by hand I would start by swapping this out for a new one.

Hightower · 13 August 2012, 00:40

Ok, I've just seen your video. Fuel starvation is the first place I would look, you could try pumping the primer by hand whilst this is happening and see if that makes a difference.

Still would check the mixing ratio of your 2 stroke.

m chappelow · 13 August 2012, 05:19

Without having a proper look mechanical wise a quick one for starts
you say the plugs are fine ! have you Put a new set in ,, I had a similar same problem with a just about brand new engine
It would start and run fine up to about half throttle then would go on one cylinder and loose power and run rough until I eased the throttle back and it then ran on all cylinders and power resumed ,, checked plugs ,, good strong spark , but same symptoms happened again ,,
Put it the spare set and it ran fine ,

On closer inspection at home noticed that the very small ceramic insulator tip on one of the plugs was loose and was sliding up and down the electrode with vibration then shorting out the spark until the engine went on slower revs and it vibrated back Ito it's correct position and sparked correctly .

jezza2011 · 13 August 2012, 09:06

I had a similar issue on my mariner 75 2st.
turned out to be the stator coil breaking down under load.
ran fine up to 1/4 throttle. Then dropped and ran very very badly like yours is.

but go through the the usuall checks.

Tom465 · 13 August 2012, 09:55

Morning,

Sorry I don't think I was very clear. I have a auto lube so the oil is in a separate container. What I meant is that I had a fuel tank with a oil mix of 200:1 which I used.
So more oil not less, didnt think it would make a difference with such a low ratio...

Yes I have pumped the primer and make no difference

I guess I will start with the simple and swap out the plugs and swap to another primer..

If that doesnt work I guess im going to have to take to a mechanic

Peter_C · 13 August 2012, 20:33

Quote:

Originally Posted by jezza2011

I had a similar issue on my mariner 75 2st.
turned out to be the stator coil breaking down under load.
ran fine up to 1/4 throttle. Then dropped and ran very very badly like yours is.

but go through the the usuall checks.

My 40HP Evinrude played a nasty game on me. Ran great at idle and anything past about 1/3 throttle it would start missing and cutting out horribly. Back to idle and it ran like a champ. Sure acted like a fuel cut, but after testing everything I possibly could I made an educated decision and replaced the black box, aka the ignition control module. Problem solved!

If it is a fuel problem propane for a couple of seconds down the carb intake should tell you if it is lean or not. Don't run it off the propane very long though as it is not being lubed properly.

If the propane doesn't make a difference it is going to be electrical. Start testing the stator, checking wiring, etc. until you find the problem or can make an educated guess as to what part needs to be replaced.

lockieboi · 19 August 2012, 11:49

I'm experiencing this as we speak.

Engine is fine until full throttle then after a while at full throttle it dies.

I've noticed that the fuel primer doesn't stay firm.

Should it and could this be the answer?
Thanks

Tom465 · 19 August 2012, 13:13

Well I guess that could be your problem.

For mine it turned out to be low oil. My oil tank had about 1/3 left in it which is enough for about 5 more trips out for me and looked fine.

Turned out when I was cruising along the engine was level and then when I went WOT the boat rises up and would think that I had low oil. It would lower the limiter and would then decrease the lower the oil is.

Jizm made a comment about the "get you home mode" so I thought id just fill up the tank to see if it made a difference. Went out and she was fine !

Note to self, have more than 1/3 oil in the tank

Big thanks to Jizm or I would still be trying to fignure out what it could be....

Peter_C · 19 August 2012, 16:38

Quote:

Originally Posted by lockieboi

Engine is fine until full throttle then after a while at full throttle it dies.

How does it die? A slow smooth death, or a fast cut? Or does it start miss firing badly then die? Is it a complete stall, or does the motor return to idle?

Quote:

Originally Posted by lockieboi

I've noticed that the fuel primer doesn't stay firm.

Should it and could this be the answer?
Thanks

Have you tried pumping it and then seeing how the motor runs?

lockieboi · 19 August 2012, 17:14

It's as if I've throttled back and then it just stops.
It doesn't miss fire or chug and splurt.

I did try squeezing the primmer bulb whilst at WOT and it still cut out.

I wonder if it's just something simple like the carbs need cleaning.