What's inside a Fountain Fuel Tank?
 

My Starboard engine runs out of fuel around 4500. When the rpms fall back down to 3000 rpm the fuel catches up to engine. I have new fuel pump and everything was running fine. Went to check anti siphon valves and found none on top of the tank. Trying to get the 90* elbows off the tank to see what is on the end of the fuel tank pickup. Scared im going to twist off the threaded stub welded to the tank. Kinda wanted reassurance that it is imperative to get to the fuel pickup to check for blockage and that risking twisting the elbows loose was needed? and what is inside a fountain fuel tank? Please give me your thoughts.

Have you tried swapping port and starboard hose to see if it is really a pickup issue?

If you have the mechanical fuel pump ran by your impeller pulley, how is the condition of the cam that runs the pump?

if you think the inlet screen is clogged on the pickup tune you can try blowing some compressed air back though it...just make sure you have the fill port open and dont go crazy with the air...just some short bursts...you dont want to pressurize the tank too much and cause it to crack/burst

I agree with swapping lines to see if the problem switches to the other motor 1st, and blowing air thru it. I believe that may either dislodge any buildup, or blow the filter off the end of the pickup tube. I'd assume any crud then picked up will get trapped in the fuel sep???
Have you put a press. gauge inline to see for sure?

I have used a small shop vac in blow mode to blow air through the tank. Kinda prevents the blowing up the tank concern

Swapping port and starboard idea is good, but so much trouble to get to lake to see if the one side is the problem. With the boat 14 years old and I want to clean everything up in the fuel system. I have all new everything on these new (rebuilt) motors. Fuel pressure gauge is on the fuel log below the carb and shows a solid 8 psi when at idle. I can't read fuel pressure when hatch is down underway. However, I have fuel flow senders upstream of the fuel pumps. The problemed engine is only getting about 10 gph vs the 25 gph versus the good engine at 4500 rpm. Looked everywhere in town today for 1-1/8" crows foot wrench to take the 90* fittings off and no luck. Fabbing up a piece of steel with a nut on it to get into the access port. If i can't get the fittings off, I am going to resort to the compressed air and take the gas cap off while blowing. Good ides from you all and I will post up my progress tomorrow. Thx Brian

All right this is what my fuel pick up looks like!
 

Took some doing with piece of welded up tubing to make a tool to get the 90* fittings off. You can see the fuel pick up has no screen. Went to the filters next (yeah, probably should have replaced the simplest item first). Look at the trash (aluminum shavings, bugs, etc) that came out of just one filter that was emptied into a five gallon bucket. The trash you see is just from pouring the fuel out. Betting the filter has even more debris lodged in the pleats. I am hoping this was my fuel starvation problem. Will post up after trying a run this afternoon.

if thats not it check your fuel line from tank to pump.

Do you have the mechanical or electric fuel pump?

On the electrical ones there is a small inline screen, if you have that much junk in the separator you might also want to check at the pump.