Dropped RPMS

" I was under the impression that the aft tank feeds the starboard engine and the forward tank feeds the generator and the port engine."

The forward tank feeds the port engine and the aft tank feeds the stbd engine and the generator"

Yes, the 93 - 46' is set up the same way. Is it possible someone ran the racks and set the fuel modulators ( if equipped) incorrectly? They can starve the engines for fuel if they aren't adjusted correctly. It's easy to move the control arm completely out of position to bypass the modulators if you want to remove that possibility from the equation.

Sounds like your fuel vents may be clogged. That or you have a turbo issue. you could try running the boat with the fuel fill caps open. On the 50' Post yes, the cockpit tank was drawn down by starboard engine and port engine drew down forward tank 2001. Fuel should NOT syphon to the forward tank unless if your fuel transfer pump has a bad impeller, but I'd keep the easier valve to get to closed unless using it.

The rack is controlled by boost pressure.
I was thinking by-pass blower issue but Skippy J may have a good thought on the turbos.
Still not enough boost, rack controller (modulator) may still not open up all the way AND NO black smoke as usual turbo issues.
Getting into more extreme theory, one engine may be holding down the other.
That supper boost (for lack of anything else to call it) does not come up till the last 4-500 RPM.
All of these can be checked with charged air pressure gauges.
I can't find my air pressure gauge installation pictures. One gauge per turbo and and air-box gauge.
Helped me figure witch turbo failed on us last year.


Skippy J has another good point about blocked fuel tank vents. In storage, bugs or storage tape over the vents needs to be looked at.

The rack is controlled by the governor. The modulator keeps the rack from going to full fuel until boost pressure is adequate to burn the fuel without smoke.I would completely disable the modulators and do a test run. I can't imagine both turbochargers failing at the same time. I also still wonder how clean the underwater gear actually is.

Maybe I should of typed the rack is limited my the modulator instead of the rack controlled by boost pressure.
That may read better.
However it's typed, it's not making HP till there is lots of air pressure in the air box, then fuel flows.

Hummm
My props should be ready at TCP this week. Maybe I can visit?