Fuel issue port side motor -- changed fuel pump / fuel pressure regulator still cannot get to 43 psi -- 40 psi only when throttling to 1500 / 200 rpm's pressure goes to 35 psi -- Starboard motor checked and fuel pressure is steady @ 43 psi -- note parts that were replace on port motor were not OEM Mercruiser -- any ideas would be greatly appreciated thanks Rich

Check for restriction in fuel line between the tank and pump.

Fuel/water separator new for the season?

Could also be the pick ups in the tank. I had some issues on my 6.2 boat and turned out the pickups were sucking air in the tank. Depending on the boat's age you might want to run new fuel lines between the tank and the cool fuel units as well. I think it cost me like $50 for new lines, well worth ruling out cheap easy stuff.

Thank you Captain ... we will be looking at the pick ups next and also replacing the fuel lines as well ... will keep all posted on root cause and repair thanks again

Yes sir new Fuel/water separator ... when replaced no evidence of water in fuel thanks for the info though

Captain also when idling @ 900 rpms if I remove vacuum line from fuel regulator PSI goes to 43 psi on gauge ... put the vacuum line back on regulator 40 psi or less ???

Look similar to this?

https://www.youtube.com/watch?v=QEa6kp5kOQg

If so, the fix was new pickups, fuel line and I needed a new fuel pressure regulator. I'd do the first two, then if having issues still, swap regulators.

Worth noting these were my 6.2s punched out to 383s and they were tuned to that fuel pressure. So it's lower than what you should expect. But still, same fuel system for the most part.

Hello again Captain ... yes looks very familiar ... so I am searching where and how on this boat to gain access to the pickup tubes in the fuel tank ... headed out to the garage and take another look ... any help or knowledge would be greatly appreciated thanks Rich

I've never looked on a Fountain but mine was under my back seat floor on the Sunsation I had. I suspect yours may be the same.