Re: 2003 yamaha 150 v6-2stroke... rpm problem
what we are gonna do here is start with the basics.
if this motor suddenly showed up at my shop I would start with a compression and spark test.
first order of testing is to insure mechanical integrity and can the ign system generate enough secondary coil voltage to spark the plugs.
by your model number you have a 2003 150 with trim and its a 25" shaft.
this motor uses a "smart" system .
2 pulsers fire 4 cylinders and the other two are "made" by the crank position sensor.
lose a pulser and code 13 is set and ECU goes into bypass and you lose the CPS signal.
means now only 2 cylinders spark.
however this system is dead reliable and rarely fails.
do a forum search on a homemade spark tester.
most our issues revolve around fuel and todays mandated stuff made it way worse.
from here at my shop I would do a fuel system vacum test with my fuel system in a box, if that passed I would open up the carbs and replace the fuel pumps.
however you most likly dont have this.
your next step is going to be turn the key on,insure the remote oil tank is at least 1/2 full, cut the strap on the engine oil tank water drain and using needle nose pliers carefully push the tube off.
sometimes lightly heating the tube with a hair dryer softens it and aids removal.
with the key still on drain the oil into a suitable container until either the tank is empty or the alarm sounds.
if the tank empties and the alarm does NOT sound we have an issue.
if the alarm sounds replace the tube and count how many seconds it takes to refill the engine tank and the transfer pump stops.
anymore than 180 seconds and we have an issue.
what I am looking for is the alarm sounded,3 bars flashing on your tach,the engine oil tank refills and quits in less than 180 seconds.
this will tell you the alarm system and oil control circuits are working properly.
if not we fix that first.
ok, I will assume all your tests passed.
now we know the ign system is capeable, the engine mechanically can make power,the oil control and transfer can work as designed and the alarm works.
now the next test is tricky, what we want is to tee in a vacum guage at the lower lift pump intake.
now we are going to run the motor on the lake at the speed it fails, if vacume exceeds 4" HG shut it down and idle back, DO NOT keep running.
now we would know we cannot supply the pumps with fuel.
remember most tank draw tubes have a screen, fuel lines can collapse and the engine cowl connector has an oring that can swell and shut off fuel.
IF you have access to a KNOWN clean good 6 gallon tank you can try the above test hooking the fuel line from the remote tank directly to the engine mounted fuel filter bypassing the cowl connector.
if the engine turns up fix the delivery system if not its carb/fuel pump time.
dont do one without the other.
another quick test to see if a needle is stck is to remove either the carb bowl drains or the carb main jets,the former may be a 10mm hex with a slot the latter is a 12mm hex.
dont lose the metal gaskets usually thay can be reused.
any questions please post but no PM concerning technical stuff
if I was smart as DonS I would figgue out how to add that to my tag line.
