Try replacing all rubber lines from fuel tank to pump. Being a 2007 hull manufacturer might not of used good ethanol hose. Inside will get soft and collapse under suction.

Thank you, will be looking at those today. Owners Manual actually speaks to the federally mandated Anti Siphon valve, that the fuel line connects to top of tank. That has a spring and check valve like ball in it, can get worn, corroded, etc and not be able to collapse the spring to get fuel flow.

Anyone know, is there special thread seal or other that needs to be used when replacing? There's some beige putty color thread seal on there now...

I use this on all automotive/marine pipe thread fittings, gasoline/oil/water/coolant
Available at pretty much every auto part store

https://cimg8.ibsrv.net/gimg/www.off...970bf4ad5.jpeg

So, wasn't able to get a psi reading off the rails, maybe my guage i was using wouldn't depress the shradder valve, but I had three experts yesterday all quickly come to the same conclusion that given there is fuel contamination in my mechanical fuel pumps, that those are the problem.

The high pressure pump can't draw deom the tank, so if a bad mechanical fuel pump isn't providing on the suction side, the hi pressure pump can't pull the fuel around and up to injectors.

New pumps have been ordered, along with new fuel line to be run from the tank to each pump. Even the fuel line manufacturer agreed after 14yrs, its time to replace the lines off the fuel tank.

Will post update once new pumps installed.

What do you mean by "fuel contamination?" They all get gas mixed with the oil somehow. Everyone I have talked to says it's normal for the lube to be diluted with gasoline. That's why it's so important to change the oil.

Exactly, mine has always had that contamination issue, hence the frequent gear lube change for that pump. Merc says it shouldn't have any, but we all know they did a poor design.

For the $150 each engine, new mech pump and fuel line to tank going in, with a prayer it solves my issue...

Well, I replaced the mechanical fuel pump in port engine, and still no pressure. I will say its really odd how the arm of the pump sits in the cam chamber of the sea water pump, and the slip ring is lose. When it was all in my hand, I could spin the ring around the cam shaft. I was told thats how it is. And is slightly eccentric so does its job.

Blead the system via shradder valve on rails. Also, fuel water separator has fuel, but I took it off, topped it off, turn key on, pressure builds. Was able to do this several times and got psi up from as low as 3 to 17, just with key on and off.

Boat is near San Antonio, TX. I dont have a qualified mechanic near me, so will have to find someone and make the haul....haven't changed pump yet on starboard engine.

So frustrating....

Ok, I write with wonderful news!!!! Just as I was throwing my hands up, the last thing that I could do is change the fuel line from the tank to the mechanical fuel pump. So, I did, and OMG!!!! Problem solved!!!! The line was restricted from collapsed inner liner, like a blocked artery! Even the manufacture suggested the change when I bought the OEM replacement line (Trident 3/8"). The fuel line was dry when I removed it and I couldn't blow air through. The anti siphon valve working perfectly. So, with new fuel line, new mechanical fuel pump, new filters, the ole 525 should be singing again! After the change, psi reading went from 3psi to 40psi just with key on!

Thank you ALL for all the responses, ideas, information, etc. This forum is an amazing resource for all of us!

Best,
Ian

Yay!!! Congratulations. Now go boating!:thankyouthankyou::evilb::coolcowboy::bunn ydance::drink::riding::p:party-smiley-048::cheer::circle::):boat: