Dont I know it, kind of knew what I was letting myself in for, wasnt expecting so many p!!s takers in the marine industry but you live and learn the hard way sometimes.

Currently at 50psi engine off, equates to very high 40s when under load, confirmed as the right way to go when the current mechanic actually bothered to contact Raylar for advice instead of just saying they couldnt get hold of them like the last place.

Did you take off all the cool fuel or just install a fuel pump and regulator?
What program is on the ECU? Raylar or Whipple?

Eventually, you will have to get a seasoned pro to read the plugs (the correct plugs) or get an O2 meter. Once you run a separate fuel pump and regulator I believe the correct fuel pressure is in the 44-45 "range" and that is still conservative on my engine.

Cool fuel is gone. Installed a larger Racor filter in line with tank then Fuelab pump and filter down in the bilge then up to Fuelab elecronic regulator on engine which feeds fuel rail and bypasses back to tank, no issues with priming or keeping up the fuel pressure now.

New ECU was sourced in US by Whipple and flashed by them and arrived here last week. Seemed to solve all remaining performance issues.

Was looking at finding a way of installing O2 sensors or testing with a temporary tube type system that pokes into the exhaust as I saw on here a while ago but then the noise became the priority to work on.

What exhaust do you have?

CMI Etube. They have the temperature sensor ports but no ports to fit O2 sensors. Saw somewhere on here that people holesaw the exhaust, dimple the two layers together with a pall pein hammer, weld the layers together, pressure test then weld the ports in as needed, could go that route.

https://www.offshoreonly.com/forums/...sor-bungs.html

I will call Larry one of these days. There has to be a reason for the 50PSI thing. Myself, SD Fever and Rage all spoke on this in detail in PM's dozens of times. We were all in the 43-44 range. Heck, SD Fever was up over 540 cu in with the dry cam and was still only at 46 or something like that....

A simple plug reading done correctly can get you closer than just setting it at 50PSI. I mean at these pressures you are leaving 75 or maybe even more horsepower on the table.

Id be interested to hear the results of your call. Last thing I want is to waste power.

Currently engine is out of the boat, the source of the noise couldnt be found under the valve covers so they're looking in flywheel housing and then onto the sump. Haven't got a good feeling about this.

The 50psi is for a HO525 kit that is using stock Merc 496HO pcm. The 7psi bump in base fuel pressure brings the A/F ratios back into a safe range.

John, Do you have any info on the Whipple pcm? What calibration/tune? I would hope it had a base tune for your setup and not just an 496HO tune?

02 bungs in the exhaust, log data, custom Whipple tune for your setup is the safe way to go. Hopefully your current problem is an easy fix. Good luck.

No info on the ECM sorry, but it is 100% the correct tune for this Raylar engine and not a stock 496.

Thanks for the good luck but Ive just been down to the workshop and based on finding a lot of fine metal in the 25 min old oil which was changed before a short test at the start of the week and a broken oil pickup, the engine will now be completely stripped and checked. The size of the metal looks like hopefully it was caught in time. Cause of the noise still hasnt been found in the upper or lower end but the investigation may have prevented the engine eating itself completely from the inside. Compression now low on two cylinders and white deposits found on two spark plugs in other cylinders, looks like oil burning, also signs of moisture inside engine, head gaskets? Mechanic seems confident the engine is still salvageable worth rebuilding so far so will keep working with it.

May now be some time before Im worrying about fuel pressure but its something I will come back to, if theres performance there to be had Im interested.