Engine stalls at high RPMs

[dptran11]

My '99 225 hp VMAX would not run past 5200 rpms this weekend (57mph). It's always been able to max out at 6000 RPMs (70+ mph). Engine idles smoothly and runs smoothly but after running at any speed above 50 mph for more than 10-20 seconds, it stalls and comes to a complete stop, then revs up again and stalls again. Primer bulb is hard, I've changed the fuel filter and have tried new tank of gas....all without any luck. Any ideas would be greatly appreciated. Thanks.

[Stratos21]

Pat, try look at 5 or 6 post down about the o2 sensor cleaning that might help ya.

[dallasdawg]

Check and make sure the pickup lines in the tank aren't too long. I had similar symptoms with my yammy. One tank the hose was too close to the bottom of the tank and restricting flow.

[sarmst100]

Mine did this when I first bought it. It could be the high pressure fuel pump in the VST although I hope not, they are expensive. Try cleaning or replacing the screen at the bottom of the pump in the VST first. You can find it at boats.net.

Also, have you changed the fuel pump diaphams in the past 3 years? These can cause it to act a number of different ways. I found some cheap rebuild kits ($31 shipped for all three) at myoutboardparts.com. Mine are on backorder now.

Let us know what you find?

[dptran11]

The motor ran fine when I ran it wide open a month ago. I'm going to replace the bulb and lines, clean the O2 sensor, add Sea Foam and put in new plugs. If these "cheap" fixes don't work, I'll look at replacing the diaphragms. Just hoping it's not the fuel pump. Will update the post as to my results. Thanks for all the input.

[dptran11]

I looked on Boats.net but couldn't find the screen you were referring to in the VST. Could you tell me which page and part number? Thanks

[sarmst100]

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by dptran &raquo;</TD></TR><TR><TD CLASS="quote">I looked on Boats.net but couldn't find the screen you were referring to in the VST. Could you tell me which page and part number? Thanks</TD></TR></TABLE>


This is the link. I myself would try cleaning it first. It is a screen and not a paper filter.
http://www.boats.net/parts/sea....html

When closing the VST back up, be careful not to damage the rubber gasket that seals it.

[sarmst100]

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by sarmst100 &raquo;</TD></TR><TR><TD CLASS="quote">


This is the link. I myself would try cleaning it first. It is a screen and not a paper filter.
http://www.boats.net/parts/sea....html

When closing the VST back up, be careful not to damage the rubber gasket that seals it.</TD></TR></TABLE>

It is part #23.

[dptran11]

What I've tried has not worked (cleaned O2 sensor, new plugs, added Ring Free, cleaned high pressure VST screen, cleaned filter). However, found out my low pressure diaphrams are leaking so I'm going to replace those then update again. Thanks for all the advice everyone!