Power loss on acceleration

[Bullseye]

Hi,
I have a '99 150 Vmax that starts and idles great... runs smoothly at full power, if I accelerate slowly... but if I accelerate hard, it losses power momentarily, then regains it. It continues to lose power and regain it, until I back off the throttle.

I would think this is a fuel issue, but the power loss is pretty abrupt, almost like the ignition is being interupted. There is no alarm occuring though, and like I said, it runs well wide open when you accelerate slowly. I'm not very familiar with fuel injection, so maybe low pressure / loss would cause this? Any help is greatly appreciated!

[boats.net]

It could be just about anything, ignition problem, fuel delivery problem, throttle position sensor or O2 sensor.

[Bullseye]

Thanks. Although it's not consistent... it does seem to also cut out on occaission in rough water. Does that point more to any one cause?
Greg

[jb123]

if it hasnt been cleaned lately, i would clean your vapor tank hp filter.

[Bullseye]

Well... I just replaced both fuel pumps. That wasn't it! :-( I'd like to try cleaning the O2 sensor, but I'm not sure where it is? JB...I saw your post for the guys with the twin 200s (sounds like the same problem I have!) I'll try draining the vapor tank as well. I'm not sure where the filter is, but I'll try to find it and clean it also. Thanks for the suggestions!

BTW.. the problem is worse now. Engine won't reach top end. Surging gets worse after it's run a few minutes.
Greg

[jb123]

http://www.boatsetup.com/O2sensor.pdf

[Bullseye]

JB, Great link! Thanks! It sounds like the O2 sensor may be my problem.

Greg

[jb123]

either way , the o2 sensor AND hi pressure filter should be cleaned yearly.

[Bullseye]

Jb... you are the man! I cleaned both the O2 sensor and HP filter today and the engine runs great! You saved the rest of our vacation! ...Thanks!
Greg

[MyNameIsBrad]

Bullseye, I'm the guy with the same problem. I removed my vapor seperator tanks and they were ridiculously nasty. I've cleaned them out and plan on putting them back on tomorrow and trying them out.


I'm glad to hear that it fixed your problem. It sounds like we're having the same issue!

How hard was it to clean your O2 sensor? Did you just do what it said in that link the one guy had?

[Bullseye]

Brad,

I think my problem was mostly the HP pump screen, but cleaning the O@ sensor isn't too hard. The article is good! Make sure you take the steel probe holder (3 srcews) off the motor before trying to take the probe out. You won't need to disconnet the wiring then.

I used the propane torch a little more aggresively than they said in the article. A local Marina said to just use the torch and skip the "Ring Free". They said to heat the probe red hot (I didn't get it that hot!). I did use some carbon cleaner first and rinsed it with acetone, dried it, then heated it.

Make sure you clean the tube (a 5/16 drill bit works for this) and the housing.

Good luck!
Greg

[jb123]

IF you heat it red hot you will toast the sensor.... pass by it lightly to raise the temp slowly.