02 Yamaha 4 stroke 115 idling issues please help.

ShawnN

Cadet
Joined
Aug 30, 2009
Messages
15
I have an 02 four stroke 115 Yamaha. I have replaced the shift position sensor. Spark plugs and had the injectors flushed and new baskets and seals installed. Boat sometimes stumbles then stalls at idle. If I rev it up quick and back off it will do it. If I rev it up and back off slow it will idle fine. Any suggestions? Problem is intermittent and sometimes it will run 5200 rpm sometimes 54-5600. The fuel does have some water in it. I have to drain the seperator frequently. I just bought the boat and I'm unsure of the time it may have sat. Any input would be greatly appreciated.
 

ShawnN

Cadet
Joined
Aug 30, 2009
Messages
15
Also. It has a new fuel water seperator. Primer bulb. It's an 02 key west 1900cc. Tank is under the cc. Kinda hard to get at so I haven't checked pick up tube etc....
 

99yam40

Fleet Admiral
Joined
Sep 7, 2008
Messages
8,851
get rid of the old fuel and water in tank.
clean the tank and then put fresh fuel into it.
flush out the lines and clean the VST and change all filters
 

ShawnN

Cadet
Joined
Aug 30, 2009
Messages
15
Ugh. I was afraid someone would mention flushing the tank and vst lol. I guess getting rid of old fuel should have been a no brainer. I will update my results. If anyone else has had a similar issue please post your results. Thanks!
 

schematic

Lieutenant Junior Grade
Joined
Jan 12, 2008
Messages
1,102
test the TPS for linear voltage while slowly increasing throttle.
as 99yam says, be sure you have clean fuel. use a external tank for testing.
 

ShawnN

Cadet
Joined
Aug 30, 2009
Messages
15
Update. It appears to be fixed. Vst filter rebuilt injectors and a good flushing of the fuel lines. And fresh fuel. Still had a hiccup or two at first but ran it for a few hours today and was able to get 5800 rpm and it idled perfect.
 
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