Suzuki DF90 Stalls then Surges

[bkellyphoto]

I have a 2007 Suzuki DF90 with an intermittent stalling issue. At high rpms the motor will stall and slow down then it surges back to speed. It doesn't stall completely, it loses power like its starving for fuel. Never any issues at idle. Some days I can run 10-15 miles before it acts up. Other days I may only go a couple miles before this happens. Once it starts acting up it may run properly for a 1/2 mile to a mile before its happens again. No alarms or codes. I have completely bypassed the fuel tank and water separator, installed brand new fuel line and ball to run off a 5 gallon can and still have the same issue. Have also replaced old thin lines inside the motor. Have taken out VST tank and cleaned and found no sediment or debris in tank or in high pressure fuel pump screen. Has anyone else had this issue? Any suggestions before I start throwing money at fuel pumps hoping that will fix the issue?

 

[99yam40]

why not monitor fuel pressures to see if they have problems when the surging happens

 

[bkellyphoto]

How do I go about monitoring fuel pressure, and if I find fuel pressure issues what does that tell me?

 

[bryanzzz]

I understand how you feel, I'm having same problem with 2014 F90 Yamaha. Mine shut down with me twice last year, motor new, I just pumped primer bulb and all OK, changed fuel water separator just in case. But, week ago motor died 6 times, changed primer bulb and next trip died and could not get restart. Drained VST, pumped bulb no go, after 1 hour called a buddy for a tow, tried cranking one more time, fired and ran all the way in at 5000 rpm. Bought a 3 gallon portable tank, ran fuel straight to bulb and ran for 1.5 hours with no problem. Does your boat have the new EPA required carbon vapor canister, with fuel limit vent valve? Yesterday I blew compressed air into fuel pick up, shortened my fuel line from tank to primer bulb adding an extra hose clamp and primer bulb hanging vertical. Will try another run this week but also will have my spare 3 gal tank with me. Sounds like we have same symptoms but I feel mine is fuel delivery, but I'm not an expert. When mine has died the motor had been running greater than 30 minutes? I probably have less than 30 hrs on my rig. Dealer said intermittent problems hard to track down, keep us informed on what you figure out, good luck.