Fellow Captains, the explanation I've seen for this problem is that it is likely a clogged fuel filter, yet I've changed both the Racor water separator filter and the main fuel filter on the engine (separate topic discusses the mysterious 'third filter' that I so far have been unable to find on my 1991 M-35 unless it is inside the pump assembly and can only be accessed by removing it) and the problem persists. Starts fine (as far as I can tell as it has always started the same way since I bought her 3 years ago -- needs a little extra fuel to get going, then idles with a pulsing rev up and down a little at about 8,000 rpm) and runs well for anywhere from an hour to 8 hours, then chokes and shuts down as though the fuel has run out.
First time this happened I knew I had sufficient fuel, but added 5 gallons and it started and ran fine for another hour until we arrived in home port. Next time it happened after about 5 hours and I instead bled the Racor filter and it started fine, then conked out again in 20 minutes and continued starting, running for awhile, then choking out.
I changed the filters, opened the tank and checked for debris (clean as a whistle), yet this season it is choking out after only an hour or so. I now realized I don't have to bleed the water separator or the fuel line, just restart her and hope for the best -- and she has run well for another hour or two without issue. I will attempt to dismantle the fuel pump assembly below the injectors today, but there is no obvious 'cup' or in-line filter anywhere on the engine. (See photos.)
Has anyone run into this intermittent problem and found it was something other than clogged fuel filters? Could it be air working it's way into the system somehow? A bit of water making its way into the system?
Many thanks for any advice.
'91 C-36 Mk. "1.5" Tall Rig, Fin Keel, Hull #1120, Universal M-35 original (not "A" or "B")
CBYC, Scarborough, Lake Ontario, Canada