Fuel Flow Issue 318 CI 240 HP

"During sea trials last Decemb

"During sea trials last December, both engines ran up to approx 3800 RPM WOT, reasonable I guess. Boat was winterized and stored for the season. Boat was prepared for launch last week, both engines were hard starting initially, especially the starboard engine. Ran the boat 29 miles across the Chesapeake from Tolchester to Baltimore. Could not get the starboard engine above 2000 RPM. Appeared to be starving for fuel. Decided to change filters once docked. All filters are changed, fuel is up to the fuel pump, but not at the top can filter just before the carburetor. I obviously thought the fuel pump was bad, or marginal. Previous owner had a new one in the original carton. Replacede the fuel pump, even though the one that was installed looked relatively new ? As if to say, not painted blue like the pump on the port engine. First indication of a fuel issue methinks. Anyway, same condition exists, after changing filters, and fuel pump, there is no fuel from the pump to the carb. I'm looking for feedback as to where to begin my search for answers. Should be obvious I know, but I'm at wits end.

Thanks in Advance !"

"Try this: Remove the hose be

"Try this: Remove the hose before the fuel pump and blow into it. It should be flow clear (and before you turn red!) If not, something is blocking the line.

Jeff

PS: You might have a hung up/ plugged anti-siphon valve at the tank. This is a spring loaded valve that, besides causing lots of trouble, is supposed to prevent siphoning the tank dry if a line fails. Look for a "thing" about an inch log at the tank."

"I'm not sure this install

"I'm not sure this installation has an antisiphon valve, at least not that I can recognize. All hoses have threaded brass fittings, even at the tank. The only anti siphon valves I've ever seen are threaded on one end, with a barb on the fuel line side which is not the case on this installation. I'll still try to disconnect the hose and get some air into it somehow, there's not enough clearance at the tank for me to blow into the hose."

How do you know you have fuel

How do you know you have fuel to the pump and not coming out of it...? Just because some fuel spills out when you disconnect the line from the tank doesn't mean you have enough suction.

"Sorry for the late response,

"Sorry for the late response, the culprit was the accelerator pump in the Rochchester Quad. Had it rebuilt, reinstalled, all is well. Now I'm trying to understand why the exhaust noise level at idle is so much louder on the stbd. engine vs. the port. Very significant, but at speed with increased RPM sounds almost even with the port."

You might have an exhaust leak

You might have an exhaust leak in the intake manifold caused by someone not including those little metal plates in the gaskets like they should have.

Are you sure it's not an exhaust manifold leak?

Jeff

"Check to make sure your water

"Check to make sure your water flow from the exhaust is about the same at low speed. A failing pump may put out enough at higher R.P.M.'s, but not at slow speeds."

"Jeff, these specific engines

"Jeff, these specific engines haven't been monkey'd with since their install back in 89. With the deck hatches open in the cabin, they both run smooth and quiet, so I'm thinking no issues with the manifolds per se, unless there's a blockage somewhere in the plumbing of the stbd. engine. The manifolds are original, 22 years. I know they've got to be at or near end of life, and I'm not ready to replace them this season.

Ed, as far as the waterflow, I thought that too, but it's very difficult to compare the two at idle since the exhaust outlets are at the waterline, it's hard to determine how much volume is coming out of either pipe. Maybe I need to run the fuel out and get the boat sitting higher in the water to tell."

Then the manifolds are probabl

Then the manifolds are probably rotted out at the bottom and leaking exhaust.

You might want to speed up their replacement.

Jeff