engine sputters at high speed/ rpm

[mccdvm]

I have a 2005 2120 with F150 OB 350 hours which sputters when it goes high speed/rpm. Was only able to crawl my way back to the marina at around 5-7 knots. Any idea on what is wrong? Thanks.

 

[Megabyte]

...or possibly a collapsed fuel bulb?

 

[Speedbump]

You should check your fuel line. What I've seen lately is the line get all swollen from the inside inn and potentialy cause by ethanol deposit and therefore leave a small flow of fuel when you're trolling but when you try to go faster not enough fuel get's to the injectors and sputters.

Sorry if I didn't explain it well enough

But to described what the lines looked like, they looked like a snake after he eating a bunch of small eggs !!!

When I remove the line, I blew air thru it to see what was blocking it and the inside liner came out in hundreds of pieces at the other end.

I seen that on Merc and Yamaha hose line

Good luck

 

[mccdvm]

Thanks for the suggestions. Will check the lines this weekend. I was also wondering does the octane rating of the gas have anything to do with the clogged fuel line or makes any difference to the performance of the OB motor? Thanks.

 

[DaleH]

I was also wondering does the octane rating of the gas have anything to do with the clogged fuel line or makes any difference to the performance of the OB motor?

Absotunely ZIP to the fuel line or clogging thereof.

Only if running a motor like the Yam F250 (that was designed for higher octance fuel) would you at least be getting close or better than the rated colwing horsepower.

Otherwise, IMHO higher octane fuel is a complete wa$te of $$ in this day and age of ethanol crap fuel, thanks to the corn lobby :roll:

 

[mccdvm]

Problem still not solved inspite of bringing it to a certified Yamaha service shop. Screen on the fuel pump and fuel filter were replaced, but still same problem. I noticed that when I was filling the gas tank that it would start leaking gas thru the vent even though the gas tank was half empty. I had to put the gas in really slow in order to get more gas into the tank. I was wondering if this is the sign of clogged fuel vent? If so, how do I check the vent and/or correct the problem?
Thanks!

 

[TimC2520]

Have you tried running this motor at the problem RPM with the fuel fill cap off? I think that would rule out a vent problem. Just don't do it in slop or you'll fill the tank with sea water. The fact that she's burping during fill up points toward a clogged or partially clogged vent which could be the problem.

 

[Harpoon]

Typical boat mechanic. They simply guess.

Try an auxillary tank.

 

[cahuna]

I had a similar issue once, the rpm's would drop when running at higher speeds, then pick up again. Funny thing is, I could trim the boat to one side and it ran fine. Not safe under some conditions though
I think there is another filter under the hood, maybe a VST filter?

Had it replaced, no problem since.

 

[mccdvm]

I appreciate all your suggestions on this matter.
However, I am still not sure how does the venting system works in boats. Is this like the venting system in sewer drains wherein you need to vent outside? If so, how does it prevent the gas from evaporating?
Lastly, how do I access the venting system? How do I replace the vent hole on the 2120? Does it need to be ordered from Parker?
Thanks again.

 

[mccdvm]

The VST filter was replaced by the technician but still the same result. The motor would run great at high RPM only for about 5-10 minutes then starts to sputter then I would slow down it would be okay, but then I'll try again at high RPM it will be fine again for another 5-10 minutes then sputter again.

 

[DaleH]

I had a similar issue once, the rpm's would drop when running at higher speeds, then pick up again. Funny thing is, I could trim the boat to one side and it ran fine. Not safe under some conditions though.

That sounds like a clot of "fuzz" at the tank fuel pickup screen or elbow.

 

[TimC2520]

That engine should store codes I think, did the mechanic hook it up
to a laptop and check?

 

[jschmid]

I had the same problem and went through all the same guesswork re venting etc. The fuel bulb was sucked flat!

I just posted on another thread that we found a screen in the tank pickup tube that was clogged. Removed the screen and tossed it in the trash.

Ran fine after that.