'08 250 HPDI Series II Trouble

This weekend my 2008 VMAX HPDI Series II didn't run right. I'm on my way to the dealership now but wanted to see what yall thought the problem might be. Motor runs PERFECT up to about 5700-5800 RPM. Once you get above there it's like it is getting starved for fuel. Sort of on off, on off. It's almost as if you were getting on and off the throttle. I figured my fuel bulb wasn't pumped hard so I pumped it a few times and tried again. It did it again. Each time it would stop and run perfect if I just backed off the throttle a little. Any ideas? TIA

Sounds to me your hitting the rev limiter and the tach may be off a bit.

Sounds very similar to the problem I had earlier this year with the High Pressure Pump Strainers being clogged.
Started fine and rang good up to about 3800-4000 then she would start bucking on me. Easy to clean/replace the strainers since Yamaha won't touch them.

But it sounds like a fuel problem for sure.

I'm with Legend on the limiter since it runs fine up to 5700. Sounds to me like he is actually over 6k and bumping the limiter. Have you lost top speed?

Plugs. Mine did the exact same thing at 5900-6000 rpm. Changed the plugs and ran perfect

How many hours on it? My bet is you have a fuel filter just beginning to clog up. And I would bet on it being the strainer between the VST and high pressure pump.

200 ish

At 200 hrs it's going to be a fuel filter problem most likely. If you brought it to a dealer, and they say it's something other than a filter problem, come back here. If you haven't brought it in yet you can fix it fairly easy if you have some mechanical skill. Read the posts pinned up top and the post on this page about high pressure fuel pump - vst
And if you've never had a tune-up, it's time.

How much should I expect to pay for a tune up?

I've been out of the biz for a while and couldn't give you an accurate answer. Just call any dealer and they'll tell you real quick. From other peoples posts on here, changing out ALL the filters can run from 375-500, it's different depending on what part of the country you are in.

"Sounds very similar to the problem I had earlier this year with the High Pressure Pump Strainers being clogged.
Started fine and rang good up to about 3800-4000 then she would start bucking on me. Easy to clean/replace the strainers since Yamaha won't touch them.
But it sounds like a fuel problem for sure."

The exact same thing happend to me and this is what it was.

Filters first, then plugs if you have not done since you've had the motor.My guess is the high pressure filter on top the motor,it's also the most expensive...go figure.. http://www.bassboatcentral.com/smileys/doh.gif be sure to post your results..

The strainer filter for me! 75.00 bucks! http://www.bassboatcentral.com/smileys/smile.gif

Update, filter and screens have been changed/cleaned. Test drive and motor still losing fuel presure at high speeds. VST "pump" is next area to look at. At least now it's warranty work going on although I'm sure my bill for the other stuff will not make me smile very much. Worst part is that the boat is currently for sale and this isn't helping!!!!!!!!!!!

I would seriously take a look at the little strainers in the High Pressure Pump

Got a new VST coming in from Japan

fuel filter

New VST? http://www.bassboatcentral.com/smileys/doh.gif I'll give you these 4 little screens for the old VST http://www.bassboatcentral.com/smileys/Laugh.gif

http://www.bbcboards.net/zerothread?id=630903