yamaha V150 surge

[mpd7510]

I have a 2005 seapro bayboat with a 2004 V150 2 stroke. Has allways run great has about 40 hrs it. I hav'nt run it for about 2 months (stays in enclosed building) pulled it out put in water cranked up and idled perfect, when I went to plain off as I got to 3000 rpm it started bogging down, bcked off throttle and it picked up power again run good to 3000 rpm as I gave it more throttle it started bogging down again. Changed plugs and fuel filters went out and tried again. Same thing happened, bogged down at 3000 rpm. In neutral you can run up to 4000 rpm no problem. When running boat it will bog down at around 3000 rpm, had wife pump gas line bulb while running and was able to get to 3600 rpm wife said bulb was getting soft. HELP!

[jb123]

if your motor set up for the couple months you most probably have to clean carbs.
if your ball is not staying primed then you must have a blockage behind it or ball valve is bad, open fuel tank while running to see if that helps as your tank breather/vent may be clogged.

[Ken]

mpd',
Have to agree with jb in that your carbs are probably clogged - mainly high speed jets.
I would try shock treatment with SeaFoam or RingFree first to see it that takes care of the problem. Also, if you can get to them, remove the high speed jets and squirt some Berryman's Chemtool into the orifices - that may help also.
If none of the above gets you above 3000 rpm, you will probably have to remove carbs, teardown, and clean.
With the primer bulb getting soft, it could be that there is a restriction from there on back to the fuel tank - maybe vent hose crimped somewhere.
Try what jb said - temporarily loosen the filler cap a little to see if there is a vacuum forming.
Also, if there is an anti-siphon valve on the tank fuel hose, they are known to stick and restrict fuel flow. Remove and clean or replace.
Usually if your rpms increase when you pump the primer bulb, that means you have a weak fuel pump(s) - not likely, since your motor is only two years old and 40 hours - but keep that in mind.
Hope this helps [img]smile.gif[/img] ,
Ken K

[RCL]

My year 2000 2-stroke 150 displayed similar problems and finally traced to one bad fuel pump. (It has 2 pumps.) The fuel pump diaphragm had a hole in it, but I replaced the entire pump. The bad diaphragm also allowed raw fuel to enter the crankcase resulting in raw fuel ejection at idle speed. My engine is fuel injected.

[mpd7510]

Thanks, Ken
your advice was dead on. I added the seafoam to the gas and sprayed chemtool into the carbs several times while it was running. Took it out and brought it up to about 3600 rpm before it tried to bog then I hit the choke a couple of times and it cleared up and ran fine.

[Ken]

mpd',
Well, you are headed in the right direction [img]smile.gif[/img] .
If you haven't de-carbed that 2-stroke in the last year, I would go ahead and do it with the shock treatment. Not only will that de-carb the motor, but will also clean out the fuel system.
Spraying Chemtool into the throats of the carbs does not clean them internally.
Also, if you don't already have one, you need to install a 10 micron water separating fuel filter in the fuel line ahead of the primer bulb. I just did mine - Racor, which I think is the best.
Good luck [img]smile.gif[/img] ,
Ken K