Surging engine

[Korourke]

I posted last week about my Johnson 175 hp 2002 was surging under load all fuel hoses have been replaced and I hooked up a portable gas tank and the engine ran with no problem so I was certain it was the fuel pickup tube I pulled it out this weekend about 31/2 feet long with a spring inside the tube and 2 inches of screen everything was clear ran the boat still surging opened the gas cap no help then when it started to surge I pumped the fuel bulb and the surging stopped looks like the fuel pump is have difficult picking up fuel the bulb goes soft and the fuel empties out could I need a stronger fuel pump it was replaced 2 months ago and siphon valve taken out the VRO was disconnected so I mix my fuel this reall has be stumped,any help would be appreciated I had this boat 4 years now and this year it started

[dbiscayne]

sounds like it could be sucking air into the fuel line somewhere. Did you run it under load with the portable tank? I've never heard of a pump only being strong enough to pull from a tank closer to the engine/shorter fuel line but theres a first for everything.

[Korourke]

I ran the portable tank for about 20 minutes under load with no issues I hooked back to boat tank surging started that’s why I felt positive it was the fuel pickup but when I got it out it was clean ,all fuel hoses replaced , this is one for the books

[dbiscayne]

any chance theres old fuel in the main tank. Try getting some of that fuel into a clear container and let it sit a few hours, see if it separates from any water.
Also do you have a regular marine screw on filter? If so was the portable tank running thru it? If not, change that filter, and also check for any obstructions that might have got caught in those fittings.
Finally, if the portable tank wasn't running thru the filter, try going through that exercise again running the portable tank to the filter housing then to the engine.

[Korourke]

After one year problem solved engine was surging when I approached 4,000 rpm’s I replaced the fuel hoses, thermostats, pickup tube hooked up portable tank and the boat ran fine so I figured the problem was forward of the engine , not so the VRO pump had a hole in the diaphragm that was the issue works in conjunction with the fuel pump even though I mix my fuel and oil together