60 hp 2 stroke feto (1999 I think)

[stevecarol]

Got this motor on a 15 foot sporty, been nothing but trouble and a money pit,
Has been serviced 2 times with different guys(no one seems to know what there doing here (Turkey) Carbs have been done,one plug lead was found to be faulty that has been changed, Plugs changed, thought it was going to be ok after that issue so took it out and then had a major starter problem, that has now been replaced.
Starts with no problems and runs very well but will not get to full throttle, pretty sure this is just a linkage issue, so can deal with that, when running at around 3/4 power(no rev counter) it will run for around 5 mins and sounds great, it then starts to hunt and cough before what seems like dropping down to just 1 cylinder, Thought it may be a oil tank sensor so messed with that, didnt find anything, put back together and she started and ran great, again for the same amount of time, have done this now a few times and each time after fiddling with the oil tank all was well for a few minutes, I have checked the oil sensor and that seems ok and there is no crap in the oil tank, the engine temp is not getting hot and the water is flowing thru engine ok and is not hot. can I disconnect the sensor and if so can anyone tell me what wires I disconnect and connect, or any other ideas as to what the problem could be.Thanks Steve

[madharchod]

replace the oil sensor in the tank

[99yam40]

you need to be testing things not just messing with this and that.
Does this motor have the alarm system on it and does it work?
Is the buzzer sound when problem happens?

Sounds like a fuel problem, but hard to tell from what you posted if loosing spark, timing is retarding, or you are loosing fuel to one or more cylinders

[stevecarol]

No buzzer sounding, no fuel loss that I can see,near on impossible to get any spares here in Turkey and would have to bring parts over from the UK,
Can the oil sensor be disconnected to bypass it.
What would your sequence be to try and find the problem with the fuel

[boscoe99]

Remove the air intake system. Move the throttle to the wide open position. It is easy to see if the throttle valve(s) are being moved to the wide open position or not.

The other problem sounds like it might be a fuel starvation issue. Plumb the motor to a small portable fuel tank. See if the problem goes away or stays. If someone pumps the primer ball continuously while the motor is being run wide open does it continue to run normally? Perhaps the fuel pump is worn and is not up to the demands of supplying the fuel needed at WOT.

Does the alarm system work? If so, you should get an alarm if there is a low oil quantity or an over temperature event. Sounds as if you have ruled both of these out. Why the continued focus on the oil system? If you had the appropriate Yamaha tachometer it would have told you what the issue is (oil or over temperature).

[richie66]

my 30 horse was having the same problem took the fuel pump apart on diaphragm looked like a saggy tit and the other had a tiny tear in it replaced and all was well might want to check that maybe you will get lucky like I did.

[stevecarol]

Thanks to all that replied with help, just to let you know all is running great now, cleaned out oil and fuel tanks,replaced bulb and fuel line, installed an inline fuel filter(there was not one fitted before) still a very small issue with filter emptying at WOT(but not affecting performance yet) so will change pump seals and diapham later when I get back to UK as a nightmare trying to get the parts here in Turkey.
Cheers Steve

[rodbolt17]

its normal for the engine filter,or any filter on the suction side, to be about half full when running.