You could remove the stainless line between low pump and VST and make one with barbed fittings for testing. Get a pressure gauge to check fuel pressure (4-7 psi). IMO, a vacuum gauge would be good for idle to check for a leak.

Ok. Next step...validating proper low pressure fuel to vst tank. The low pressure pump has 100 hrs on it. I know that doesn't mean much, but I did replace it when I purchased the boat.

I believe you answered your question.

Recheck fuel psi at WOT, it should be damn close to what it is at idle with vac removed from regulator.

And yes, with the ret line blocked off you sould see much more psi than with it not blocked. This tests to see what the pump can push against.

I will recheck fuel psi at wot, and all other scenarios. Helps to write all this down and re-read.

Thanks again.

If it is a lean condition you may of hurt the engine last year, I think you need to be closer to 40psi on the rail

As stated, verify your fuel pressure.at WOT. If it checks out good, then do a leak down. My guess is if it is not fuel related you are due for a valve job.

Just had a thought. last season, the loss of power was accompanied by undesired sounds at Higher rpm (not mechanical, but almost sounded like detonation). At the end of the season, once hauled, I found the rotor was cracked at the stem where it sits on the distributed shaft. I replaced the cap and rotor and put the boat to bed for the winter. Of course it seemed to run great on land and with no engine load. Could the ecu possibly have relearned an ignition curve and now needs to be re-calibrated? I don't mean to get off the fuel delivery topic, but this timing senerio just occurred to me. I know there could be possible engine damage, Gotta rule out the other stuff first.

no, ecu isnt self learning, mefi is pretty primitive

Key on engine off primes to 25,settles to 15 starts quickly

idle with vac ref 35psi
idle with no ref 40

cruise, 33-34psi w ref
cruise 33-34psi no ref

wot 31 w ref
wot 31-32 no ref.

I obviously have a leakdown senerio occurring. Just have to figure out where.

You have low pressure and needs to be increased, should be at 37 psi, IMO your running out of gas and its lean. Even cruise your low