2014 F150A Loses power under load

[AKDNA1984]

We were traveling for a 2 hour ride. The first part was smooth and we were cruising along at 4500 RPM. The water started to pick up about 20 minutes in and to about 2-3ft waves and we started to gradually lose power. RPMS would not increase no matter how much throttle i gave it. It got as low as 3900 at one point. Once we got out of the chop at about 1hr in, I kept it pinned. The RPMs slowly started creeping back up to 4500 and stayed there. Since we were in really calm water I slowed down to idle and then got back up on step no problem and was able to go WOT at 5600. I backed it off a bit to 4700. after about 10 minutes I started losing RPMs again and couldn't keep it above 4400 the rest of the ride.

Once we arrived I drained the VST tank and got some gunk out of the tank. It looked a little like sediment and bad fuel. Once the fuel that was draining out looked clear I tightened the drain. I also checked the Racor Water Separate and the engine mounted water separator which both looked ok I tried to clean the two filters the best I could. I took it for a spin for about ten minutes and was able to get WOT and motor ran smooth.

The way back two days later was total flat water. I was able to get WOT for a bit abut after about 20 minutes I slowly started losing RPMS and couldn't get it above 4500 for the rest of the 2 hour trip back. We cruise at about 27MPH at 4500 so we were able to stay on step the whole time.

I've put some compressed air into the VST tank at the schrader valve to try to create some back pressure but still am not getting any more gunk out of the tank. Is there any danger of rupturing anything in there?

I've ordered

[AKDNA1984]

I'm thinking that the there is still gunk trapped in the VST tank and eventually being picked up by the pump and blocking the VST filter when there is higher fuel demand. When I slow down the gunk falls off the filter and allows better fuel flow.

I've ordered a new VST filter and tank gasket. May just have to man up and pull the tank and replace the filter. From what I've been reading this is a classic symptom of clogged VST filter?

Any other suggestions on things to check? Thanks!

[TownsendsFJR1300]

Sounds like you need to address the dirty main fuel tank or you'll be doing this again.

Pumping crappy fuel back into a "cleaned" motor is just putting off the inevitable.

Besides the VST filter, there's filters at the injectors which may need cleaning /replacement.


Obviously, the bouncing about in rough water stirred up crap on the bottom of the tank and then your engine sucked it up...

Good luck and plz post back what you find...

[pstephens46]

Yes VST filter can be cleaned and reused as long as the mesh is intact. As Scott mentioned, you need to start at tank first. Use marine fuel, if available, after you get it cleaned up.

[99yam40]

you have to wonder how the filters could look OK but you end up with stuff in the VST.
the whole fuel system needs to be cleaned

[slads5874974]

I had a very similar issue last year.

http://www.yamahaoutboardparts.com/f...tank-wanna-see

I lost power under load all the time. Especially in snotty conditions. Turned out that I had to clean and replace parts from my VST and just as important, I found out I had two bad fuel pumps. I replaced them both along with the VST Pump. No more fuel issues or power loss.

Might a be good idea to check those pumps.

-k