Low Fuel Pressure, High Idle

brandonmayberry

Maybe someone here has an idea. I have a 2000 Mercruiser Mag MPI 350. Eng # 0L662694. Was having issue of only being able to reach 3000 RPM and would not plane out. Hooked up a fuel pressure gauge and it would kick to 30 when key was turned and then idle at about 25PSI. Wide Open Throttle would give me about 32PSI but remember WOT was only going to 3000RPM. Also after running and getting up to operating temperature i would turn the boat off and if i tried to restart it after sitting for about an hour or so it would run for about a minute and then die. At this point the fuel pressure was reading 0 and it would not start until it cooled off completely.
I thought maybe it was fuel pump or fuel pressure regulator so i replaced both. Still will not get over 3000RPM and fuel pressure is now reading about 15-20 so its lower than before. Also i have a LOUD vacuum sucking noise that comes from the throttlebody where the hose for the PCV valve is. I tried replacing the IAC and still did no fix it. The boat is idleing over 2000 rpm Im beating my head on a wall and tired of throwing parts. My local marina doesnt have a mercruiser computer and the closest one is a good drive from me. Any help would be greatly appreciated!!

212rowboat

You got a vacuum leak... 

Figure out where that sucking sound is coming from.  Plug it.   Your likely right to swap regulator and or pump... Itshould hold steady pressure no matter rpm, or load.  If it wasn't a consistent and steady pressure at a pretty precise range, the pcm wouldn't have a clue how to trim fuel. 

brandonmayberry

The sucking is coming from the back of the throttle body where there is a hole that then leads to a hose which goes over to the starboard side of the engine valve cover and hooks onto the PCV valve. I plug up the hole on the throttle body and it kills the engine or if i unplug the hose from it leading to the PCV it kills the engine.

brandonmayberry

I also think i may be missing the IAC muffler. I think that the "hole" in the back of the throttle body is where the IAC muffler would go but i dont think that missing that tiny piece would cause this bad of a running issue.