Yamaha OX66 200 H.P........Help!!!!!!!!

[DCampbell]

I have a Yamaha OX66 200 H.P. outboard. It is either a 99 or 2000, i'm not sure but it's on a 2000 Century boat. lately i've been having problems with the motor surging at higher rpm's, or under load. I can run the boat in flat water up to about 3800 rpm's with no problems, but when i increase throttle up to over 4000 rpms the boat surges like it's not getting enough fuel or something. It drops power then comes back, drops power then comes back. Also i can't get top end speed out of it. I've have cleaned the 02 sensor and changed all the filters (fuel/water separator etc.) and the problem still persists. If you guys could give me some ideas of what the problem may be i would greatly appreciate it. I've called several dealers and everybody's back up for weeks. Any thoughts or ideas would be greatly appreciated.

[bquick]

Could be the injector pump going out....fairly common on those.....

[DCampbell]

is there anyway to test the injector pump??????? how much $$$ would that run me???????

[Shin-Dig]

If you haven't replaced the low pressure fuel pumps start there. One of my engines had a similar problem and I replaced them Problem solved for $100 worth of part. It is ana easy do it yourself project.

[DCampbell]

What about the VST filter can i check and replace that myself?????? could it possibly cause the symptoms?????

[DCampbell]

will i see anything noticable on the low pressure fuel pumps??????? or is this something that just stops working over time??????

[parrott]

I'm pretty sure they have rubber diaphrams in them and they will get small holes in them. If it's a 2000 and they have never been changed, it's more than likely the problem.

[DCampbell]

when i replace my low pressure pumps should i check out the VST filter??????? Should I clean it or replace it???????

[Snowmon]

You can check the low pressure pumps with a mighty vac. usually don't last longer than 2 years and if you're dealing with e10 maybe less. i had to change out after 1 year with e10. i would just replace as posted earlier and an easy job. i'd also check the filter on the high pressure pump inside the vst. probably a combination of both. I assume you have a remote filter water seperator that checks out ok.

[John_Madison CT]

Another candidate for a vst filter replacement.

[gmanoffshore]

Don't forget to check the simple things. I have had 2 different motors do the same thing and it was a small pin hole or loose clamp in the fuel line near the primer bulb letting air in the system at higher RPM,s. It will not leak fuel but will let just enough air in to surge under load and at high RPM.

[loyed]

I have no idea what the cause might be but my 2001 200hp ox66 had similay problems right before it blew. I now have a hole in the block and some VERY costly repairs. My .02