Vmax 150 idle

[104460RSo]

Motor is a 2006 Yamaha V150TLR. Motor starts up and runs great, idle is 700rpm and *****ingspeed 550-600. After some time running, idle drops and some time stalls. This only happens after som time running. If I turn the idle up a bit it will run, but then next startup on cold motor the idle is to high.
Had an issue with water in fuel last year, got that sorted.
Done so far:
Compression is good on all 6
New fuel pumps
New spark plugs
Rebuild carbs, removed, inspected and cleaned all jets. New gaskets
Fuel filter and water seperator
Tank is clean, fresh fuel
Synk/link as in manual
Idle mix screws are set, port 1 1/16 Starboard 1 9/16
New check valves
Cooling is ok, have water pressure gauge

Motor do not smoke, running nice and sounds good. Only issue is idle when motor is warm after som time on the water.
Suggestions for other things to look for?

[99yam40]

looking at a part break down of the carbs it seems this motor has a manual choke, nothing automatic.
is this correct?

If so how long of run time before it idles too low?

not sure that the 550-600 was representing in you post since they knocked out some of the wording.

have you checked the timing at idle when it is running well and when it is not to see if that has changed?

how about checking spark on all cylinders when problem shows up?

[104460RSo]

Choke is on the key ( push key)
In idle it can run smooth forever, but after motor been in higher rpms the idle gets low.....sometimes after just 15min.
550-600 is rpm in gear
I have not checked my timing with a light, it's just done as my manual says to do the sync and link
I have checked that the magneto control lever returns to the stop screw when throttle is nøytral.
Have also adjusted the idle mix screws a little without any better result

[99yam40]

Have you made sure the timing lever returns back where it should when the ruff idle shows up?

A timing light would be easy to see what the timing is doing, and if you move the pick up to the different plug wires it might show if spark is not happening.

but then a spark tester would be better for that

[104460RSo]

Yes, I am sure the timing lever returns back.
Will try a timing light next time I am in the boat.

Does it sound like a timing problem I got, and not a fuel problem?

[rejesterd]

After some time running, idle drops and some time stalls. This only happens after som time running. If I turn the idle up a bit it will run, but then next startup on cold motor the idle is to high.

500-600 sounds too low. The service manual should give you the spec for expected idle speed. At cold startup, the idle should be high, and then eventually drop down to 750-800 rpm (for most engines). Why not just turn it back up a little bit? If the motor sounds/feels great when it's running, I wouldn't suspect a timing issue.

[99yam40]

timing can change RPM easily,
just something easy to check.

spark to each spark plug is also easy to check with a spark tester.

loss of spark a cylinder of two can drop RPM also

rule out what is easy to do and then chase fuel problems

[104460RSo]

500-600 sounds too low. The service manual should give you the spec for expected idle speed. At cold startup, the idle should be high, and then eventually drop down to 750-800 rpm (for most engines). Why not just turn it back up a little bit? If the motor sounds/feels great when it's running, I wouldn't suspect a timing issue.

Manual say 700+/-25 rpm. When the idle gets low and rough I need to turn the idle up a lot to keep it running, then on next cold startup idle is then way to high....like 1300-1400 rpm

[104460RSo]

timing can change RPM easily,
just something easy to check.

spark to each spark plug is also easy to check with a spark tester.

loss of spark a cylinder of two can drop RPM also

rule out what is easy to do and then chase fuel problems

Did check today with a spark tester, spark on all 6 leads, also when idle gets low and rough. Also checked again that the timing lever returns to idle posision.
Guess the next thing to do is have timing checked with a timing light

[nunleyville]

Anything further on this? I have a 2008 with a very similar issue. Mine seems to do it more so when it's cold but sounds to be very similar.

[104460RSo]

Still the same. Not a big problem for me , just irritating. At first startup, it will idle forever...sounds good. After some time at higher rpm, then the idle get rough and low.