2002 yamaha four stroke acceleration promblem

[JKNOEBEL69]

i have a 2002 115 Yamaha four stroke i live in fl i run the engine every mth even when not in the water this winter was colder than normal but ran it at least 20 to 30 minute a mth i did not add any gas or stabilizer it never needed before. i have always used it in the winter. first time out i added high test fuel ran great second time out the same third time lost power in the planning area could hardly plan off. i replaced fuel ball replaced water separator filter and clean fuel filter.ran better still having problems under load when i pump throttle i can feel a slight surge in power can anybody help. thank you.

 

[capt sam]

Re: 2002 yamaha four stroke acceleration promblem

are you using ethanol based fuel?

 

[JKNOEBEL69]

Re: 2002 yamaha four stroke acceleration promblem

thanks for the reply i will check today when i fill up i think 93 octane at exon

 

[rodbolt]

Re: 2002 yamaha four stroke acceleration promblem

use 87 octane,its what the motor is designed for.
93 is a waste of your money and can lead to excessive carbon deposits.
your describing a typical loss of fuel rail pressure due to a clogged filter in the VST.
check fuel rail pressure at the problem RPM.

 

[JKNOEBEL69]

Re: 2002 yamaha four stroke acceleration promblem

thank you for the reply i took the boat out again and added sea foam to 10 gallon of gas. has 10% ethanol i will look around to find ethanol free gas next time. ran better with changes still not right would plain off ,to keep at a running speed i would have to pump accelerator.i will check the pressure when i buy a gauge and when i find out what a svt valve. what is it? is it hard to change? and were is it located? is it under the manifold? i will try to find out more .thank you for your help

 

[rodbolt]

Re: 2002 yamaha four stroke acceleration promblem

just keep it fire walled and add more snake oil.
burns valves faster.
us poor techs need the money.
or purchase the yamaha service manual and any special tooling nessasary and fixit.
if its a fuel rail low pressure issue or a clogged injector and you continue trying to run it it can and will lead to burned exhaust valves and detonated pistons.
the vapor seperator filter is a routine maint item.
its behind the intake,intake has to be removed to service the VST.
takes about 1.5 hours.