99 F50 AET fuel problem

[macca_dylan]

Hi,

I still have a fuel problem with my F50.

So far carbys been cleaned 5 times, 3 times by different yamaha outboard mechanics, 1 time by myself with full carby kit through it, once by a carby cleaner spe******t who soaked over night and sonic bathed.

Motor is idling fine for awhile then will start to run bit rough and then you can smell fuel. Give it few more revs and it settles down again and will idle for 5 mins or so and then do the same again.

When accelatering it will miss around 1500 to 2500 rpm then will pick and run at high speed fine.

When you turn it off then go to start it again it wont start not even fire. I have to open the throttle up half way in neutral to start it, but it will slowly pick up till it revs and takes about 30 secs or more, then have to run it about 900rpm for 2 mins before I can put it into idle to put into gear. All this time you can smell lots of fuel like it is flooding or running very rich.

All mechanics have sworn to me the carbys are clean, synced right, tuned to prefection. Last guy even put it in a tank and showed me it running.

First question I ask is it the fuel I am using? I am running 98 octane fuel in it as recommended by a mechanic.

All mechanics have used their own fuel tanks to service it as they say it workshop policy.

My tank is brand new, new fuel lines, new water seperator filter, new fuel filter just before carbys.

Is there something else they are missing?

I have been told fuel pump is fine no leaks. It has been pulled apart and cleaned.

Please help as so far $1200 has been spent on these carbys and I ready to drop a match in the fuel tank as very pissed off.

Thank you in advance for you help.

[rodbolt17]

for whatever reason, your describing an excessivly rich air to fuel ratio.
to much fuel.
not familiar with non US market engines.
a picture of the carbs would help.

[99yam40]

If this motor has the prime start enrichment system instead of a choke, then you need to be inspecting and testing the system for torn diaphragm and proper operation of heater unit.

[rodbolt17]

again, not being familiar with international market designations the F50 used 2 versions of auto enrichment.
a complicated mechanical version and a version with 2 electrothermal valves.
dont know which you have.

[macca_dylan]

Hi,
Thanks for your quick responses.

F50 AET is the same as F50 TLRX well that is what I have told and have been going by when ordering parts for it. In manual every thing is the same I have both manuals and they match part for part even part numbers so far that I have found.

Would the fuel Im running make it run richer because of higher octane than tuned too?

Dylan

[99yam40]

Check enrichment system like we said before.

Yamaha says regular 87
higher octane burns slower but I do not think it would cause this type problem. Just my opinion

Just looked at parts beakdown of the F50TLRX carbs and it does not show the electrothermal valves, or an electric choke solenoid

Does this thing have a choke or is it what Rodbolt17 was calling the complicated mechanical version of enrichment system?

[rodbolt17]

the X model uses a mechanical setup with an auto half choke.
check that both are working.
carefully inspect the accelerator pump setup.