Yamaha 2004 50HP 2 Stroke - Engine die down when shift throttle to forward position.

[Seaforce]

Hi All

The engine had just been services by marine technician 2 weeks ago, with new spark and oil.
Took the boat out first time after service, the engine start fine and run great,
BUT after 1hr of fishing later, when I try to re-start the engine, the engine will start but will die down straight away when I shift throttle forward,
I need to repeat this process around 5 to 10 times ( start-die down) before the engine will run again.

The engine start/ idle fine, not hard to start,
can anyone direct me to the right direction , what may cause this problem . and perhaps how can this be fix also.

Regards,

[99yam40]

check compression and spark on all cylinders when problem shows up, or is it all of the time now?
if all 3 cylinders are good with those,
check with a timing light to make sure timing stays in spec .

check the fuel pump to make sure it is not leaking into #3 crankcase
change the spark plugs

if all those are good then carb problems ( most likely),
or something else that could affect the fuel to air ratio,( like air leaks , crank seals,crankcase recirculation valves,or reeds)

[Seaforce]

Thanks 99yam40, yeah all compression were check 2 weeks ago 120psi in all cylinder.
With new spark plug.

Thanks

[zenoahphobic]

These situations always beg the question what really did the marine technician actually do when he serviced the engine.
Spark plugs plus oil, but that is a two stroke so the oil would have been in the gear case at the end of the leg?

Prima facea it would seem he may have made some adjustment(s) to how it was before. My guess the simplest would be the idle mixture, he may have lowered the idle setting, or altered the synchronisation between the carburettors.

Sorry I have this scepticism as where I am, there are many who don’t really know what they are doing (including owners), and tend to touch things on perfectly working engines in an attempt “to fix what ain’t broke”.

[99yam40]

Thanks 99yam40, yeah all compression were check 2 weeks ago 120psi in all cylinder.
With new spark plug.

Thanks

If compression was good 2 weeks ago and the motor ran well after that ,
but then something changed after running for awhile,
and it is not running well now,
it is time to see what changed
start with compression,
then spark on each plug wire( actually the timing light will tell you that is you move it to each plug wire)
make sure the light shows the proper timing while on #1

you still did not answer my question on if it still runs well for a period of time and then does not,
or it runs bad all of the time

[panasonic]

So I am reading that the engine will start/run from a dead cold condition fine. Only after the engine has been run up to operating temperature, left for a short while, then it will require 5-10 attempts to get it running in gear....is this correct?

Are you sure that the shop did not touch anything else on the engone while in for service?

Did you try and pump the primer bulb while the engine is acting up?

[Seaforce]

So I am reading that the engine will start/run from a dead cold condition fine. Only after the engine has been run up to operating temperature, left for a short while, then it will require 5-10 attempts to get it running in gear....is this correct?

Are you sure that the shop did not touch anything else on the engone while in for service?

Did you try and pump the primer bulb while the engine is acting up?

Hi Panasonic

yeah the engin seem to running fine from cold. Only happen when stop and re-start

i am not 100% sure if the shop touch anything else.

I checked on he primer bulb its hard, when acting up.

Thanks