2013 Df300 Losing RPMs

[Jonwalla]

2013 DF300 1050 HRS, motor seems to be lacking fuel the higher RPMS. The more RPMS the quicker the symptoms occur. Boat will run fine at 4000 all day. Above 4,500 the problem occurs and the boat will lose rPMS. When i pull it back and and start again it will run fine for a short period and then the symptoms occur again. If the fuel bulb is pumped while running the boat will run fine. So far i have run the boat off another tank, changed all fuel filters, even the small one in the vst. Changed the low pressure fuel pump and the problems continues. No alarms. Any suggestions?

Thanks
Jon

[artdf175]

this is sounding like a fuel hose blockage our tank venting plugged
your spare tank- where does it plug into engine? my boat had a built in tank that runs through the fuel/water filter and continues directly to the inline fuel filter pre the low pressure pump
is the bulb fairly flat when you pump it to get rpm’s to come back?
reason for asking is trying to eliminate some of the following things
here is a short list
fuel line breaking down internally plugging up fuel flow
fuel bulb -which brings up - is it in the correct direction for the fuel flow and when mounted is it in a vertical position
clean low pressure fuel filter
condition of water /fuel filter - easy replacement every year
checked fuel tank vent for spider type nests
Art

[Jonwalla]

So that is what i thought as well it does seem like some sort of fuel blockage that is limiting the amount of fuel to the system. The small spare tank was plugged into the system right after the raycor and the problem persisted this eliminated any tank problem, bulb problem, and the majority of the fuel line. At this point all the filters are new and the problem persisted. The vst was cleaned and the small filter changed. Low pressure pump was replaced. Still having the problem.

[artdf175]

to double check the low pressure pump - take a piece of fuel line and put it on place of the line to the high pressure pump
use a container to collect fuel
I would take the plugs out - then turn it over with the starter a few times to be sure you have good fuel pressure
and make sure you have new gaskets on the low pressure pump

maintenance question - ever checked valve clearances?

I have had s couple of circumstances with loss of power I am thinking there is a spot in my bevy josevthat is trapping fuel and not letting the tank breath /vent well

might try taking the fuel cap off next time this occurs if it were something so simple it would eliminate any bunch of other speculations
Art

[Solarman]

If the low pressure pump was bad, did they remove the needle valve seat/and reset float level Possible restriction on the back side of the seat IF the low pressure pump has pieces missing?
Also, make sure no air is getting into system/filters prior to the low pressure pump (bad seals, loose fittings, etc.).
Just some other thoughts.

Good luck.

[Jonwalla]

I have not checked the valve clearances. Could this be my problem. By running the motor of a completely different fuel tank i have elmimiated my onboard tank and 90% of the fuel line.The motor runs great under 4000 rpms. I feel like there is just not enough gas being delivered, to keep up with the need at higher rpm. The harder it is run the quicker the symptoms happen. The whole vst was cleaned when the small filter was replaced. I am wondering if its my hp fuel pump?

[artdf175]

as Solarman mentioned and I forgot check clamps on the fuel lines - hoses not clamped correctly have been a problem
might try running it with the cowling off and observe the inline fuel filter should have no air in it.
the observed problems with the high pressure pump generally been associated with the filter or water
if the pump keeps the pressure up to run up to 4,000 rpm - It’s probably not the pump

you have never had the valves checked?
Art

[Moonlighter]

Dont dismiss something simple like a spark plug breaking down.... when the engine gets hot its not unheard of for a faulty plug to make its presence known!

[Jonwalla]

So it was a collapsed fuel line. Replaced it the other day and it ran great.

Thanks for all the help.

[Moonlighter]

Thanks for reporting back. Good that you found the culprit and got it sorted.

Which fuel line was it?

So many issues reported here are boat/electrical/fuel supply issues like you have found.

BTW are you having to use Ethanol fuel in your area? Known for causing internal damage to fuel lines. Can get lines that are rated to suit it.

[LPowers]

Just to add, last year I had the same issue. Collapsed fuel line from tank to outboard(that line was rated for E-10). Used E-10 half the time with Startron additive. Since replacing all 3 fuel lines, non-E fuel with Startron and no issues.