Starving For Power

[BrianAmberjack]

No I was thinking distributor advancing issue but if it happened after the outdrive swap you may be on to something there

To my knowledge the distributer does not self-advance on this engine. I loosened the hold down bolt on both distributers in order to adjust their respective timing-at-idle to 8 DBTDC, in accordance with the manual. After that, the only timing adjustment that takes place is through the "Ignition Amplifier" Thunderbolt ignition module. As I wrote in the OP, I exchanged that entire system with the known-good-parts of the starboard engine, and tested for auto-advancement by that module, up to 2000rpm. Timing did advance all the way to 12 DBTDC, and the fault stayed with the Port engine.

 

[BrianAmberjack]

Did I miss the fuel pressure test results taken at the time the problem happens?

I did not do a fuel pressure test. I felt that the more definitive test would be a complete exchange of fuel pumps and blowing out the in and out lines. I did not have access to fuel pressure gauges, so that also influenced my choice of procedures,

As well, while running, I did set a plastic rod with increments on it, into the carb bowl through an access hole and rested on top of the float, to see if the float was keeping up with engine demand. At 2K both engine had the same amount of fuel in the bowl, even though the port throttle was already creeping ahead of the starboard throttle.

 

[BrianAmberjack]

Keeping the drive rebuild on the table as a possibility...

Let's narrow things down. Let's eliminate the fuel supply issue as a variable. This will tell you if the issue is at the engine or still at the fuel supply side (thru-hull vent, hoses, tank, etc).

-- Run the engine on a portable tank. If all is good, the issue is supply. If still an issue, then we're back to the engine (or drive). You could try swapping what tank each engine runs on, as well.

FYI, put the anti-siphon valve back on - it's an important piece for safety - and required.

At the early stages of dealing with the water ingress issue, I did exactly that (removed the line that goes from the fuel filter to the fuel pump, and submerge it in a jerry can of fresh fuel) To be honest, I wasn't really paying attention to WOT. That symptom showed up after I had the water thing solved, when tried to push the throttles to get it up on plane and noticed the throttle position difference.

Next spring, when I get it in the water and have tested the new OD positions, the possible vacuum leak, the exhaust flap condition, and the intake manifold blockage possibility, I will do a definitive fuel supply test. But I have to think that all of the things that I have done to the fuel supply system would have eliminated any faults with it.

I read in the manual that the fuel supply system may or may not have an anti-syphon valve, and the starboard system did not. And so I removed it, in order to eliminate it as a culprit. When I get this issue resolved, I will put it back into the circuit, as well as installing one on the starboard system.

 

[Yendor]

It seems odd to me that you would have a anti-siphon valve on the port tank, but not the starboard.
Dumb question maybe, but are these tanks both factory, or was one added?

Maybe you did this and I missed it, but were it me with these results, I would've switched the tank feeds on the front side to eliminate that as a variable. If the fuel feed discrepancy moved to the starboard engine, then . . . well, you know.

I am a very big proponent of using the temporary, known clean, portable tank that Lazy Daze eluded to earlier. Did you do this and attain the same results?

***EDIT***
You were addressing these questions while I was asking them, now THAT'S responsive.

 

[BrianAmberjack]

It seems odd to me that you would have a anti-siphon valve on the port tank, but not the starboard.
Dumb question maybe, but are these tanks both factory, or was one added?

Maybe you did this and I missed it, but were it me with these results, I would've switched the tank feeds on the front side to eliminate that as a variable. If the fuel feed discrepancy moved to the starboard engine, then . . . well, you know.

I am a very big proponent of using the temporary, known clean, portable tank that Lazy Daze eluded to earlier. Did you do this and attain the same results?

***EDIT***
You were addressing these questions while I was asking them, now THAT'S responsive.

Not having an anti-syphon valve on both engines does not surprise me. This is a 34 year old boat, and has had at least three previous owners. Based on the condition of the electronic/electrical/engine systems when I took possession, I do not have any confidence in the technical abilities of those owners.

I have put a lot of work and money into this boat, in order to bring it up to a standard that I am used to, given my tech background. Not complaining though, I have had a blast reworking everything, and have gained a ton of knowledge and experience. I love the boating life; Bring Out Another Thousand!

 

[Lazy Daze]

I think you probably would have noticed an issue with the drive before you reinstalled it - most likely you spun the driveshaft by hand - if for nothing else than for fun And you really can't reinstall it wrong. Unless something grenaded inside... but then problems would be worse. Oh well, next season will answer that one.

You may very well be right that the fuel system supply is fine - I just like definitive tests.

Did you happen to try running with the fuel cap off? You mentioned "determined all fuel/air paths to be unobstructed and free of debris", so that probably means you verified the vent fitting was clear and that the fuel vent line was good. I know you said you "inspected" the vent line... but depending on how thoroughly you did that, there's a possibility that the hose is failing internally, creating a check valve. Running with the cap off eliminates the vent system. Just some food for thought.

AS valve... yup, on a 3 decade-plus old boat with who knows how many owners... you're smack dab in the midst of the "Previous Owner Syndrome"

If no part of the fuel system (hoses, pumps, etc) are below the level of the tank (and are adequetly prevented from falling below), then (if memory serves) you technically don't need the AS valve. But the last thing you want is something failing/rupturing and emptying your fuel tank into the bilge.

 

[BrianAmberjack]

I think you probably would have noticed an issue with the drive before you reinstalled it - most likely you spun the driveshaft by hand - if for nothing else than for fun And you really can't reinstall it wrong. Unless something grenaded inside... but then problems would be worse. Oh well, next season will answer that one.

You may very well be right that the fuel system supply is fine - I just like definitive tests.

Did you happen to try running with the fuel cap off? You mentioned "determined all fuel/air paths to be unobstructed and free of debris", so that probably means you verified the vent fitting was clear and that the fuel vent line was good. I know you said you "inspected" the vent line... but depending on how thoroughly you did that, there's a possibility that the hose is failing internally, creating a check valve. Running with the cap off eliminates the vent system. Just some food for thought.

AS valve... yup, on a 3 decade-plus old boat with who knows how many owners... you're smack dab in the midst of the "Previous Owner Syndrome"

If no part of the fuel system (hoses, pumps, etc) are below the level of the tank (and are adequetly prevented from falling below), then (if memory serves) you technically don't need the AS valve. But the last thing you want is something failing/rupturing and emptying your fuel tank into the bilge.

Will put that suggestion on my list: run with the cap loose enough to allow air into the tank. Thx.

 

[techmitch]

I know you said that you didn't have a gauge, the pressure drop would show up if the vent was clogged.

 

[Bumpo64]

Good Day Club Sea Ray Skippers. As the title of this thread indicates, I am having a problem with one of my engines. I apologize for long thread intro, and I will try to use point form as much as I can to mitigate that. I have been searching through as many forums as I can in order to resolve the engine problem, and only now, after an entire season of troubleshooting and testing, have I come to the point of having to ask for help directly from the Club Sea Ray community.

Please read the entirety of what I have already done, before making suggestions.

The Boat: 1989 Sea Ray 270 Amberjack, twin 4.3LX mercruiser engines(according to the purple aluminum tag on the carbs), Thunderbolt Ignition, Rochester 4 barrel carbs, water separating fuel-filters, anti-syphon valve on port supply line, separate fuel tanks, only ever seen fresh water in Lake Ontario. Props in great shape.

My History:
Avionic Tech from Canadian Armed Forces,
have rebuilt auto engines, replaced auto engines,
rebuilt/installed Volvo-Penta MD2B diesel system in home-built C&C 36R sail boat hull, still running great
usually do all of my own vehicle maintenance/repairs, am a newb to out-drives and marine gas engines

Operational History:

May 2021 - purchased boat, ran perfectly all season

June 2022 - ran fine but Port Outdrive impellor failed,
drained and pulled lower section,
replaced impellor,
replaced outdrive lube oil, incorrect procedure, did not put enough oil in drive
was under the impression that the out-drive had an oil pump,
assumed that the oil would be circulated through-out the drive sections, not all settling to lower unit
Stupid-Stupid-Stupid, at the end of the season (had a great season moving the Boat along the North Shore of Lake Ontario, then up the Trent Severn Waterway to Lake Simcoe Ontario) while at 4200rpm and on plane, the port outdrive began to seize, the engine slowed, I shut it down, a single back-fire, done

Sept/Oct 2022 - Broke down port outdrive, flushed lower unit clean, located/purchased/installed used matching (gear ratio) upper unit, new gasket kit, reinstalled to boat. Winterized both engines

May 2023 - flushed winterizing anti-freeze out of engines while running on trailer with muffs, engines warmed up/idled/revved well, launched at dock in Lake Simcoe and headed out, 5 min out Port engine stalls, continued on starboard engine to new marina.

The Symptoms: Fairly quickly discovered that the fuel filters both contained water, drained them both, cleaned the water out of the port carb bowl, she started right up (after the expected turn-over time to get the fuel into the carb), replaced both fuel filters with glass bowl type for easier and more frequent inspection (newb mistake, not flushing them out and regularly inspecting for water. Never had this issue with the sail boat diesel system), during sea trial she started perfectly, ran smoothly, idled out of marina as expected, pushed the throttles up, rpm/power increased, noticed prt throttle getting ahead of strbd throttle, port rpm/power topped out at 2800rpm, strbd was able to go up past 4k. and that is how it was all season

The Repair: Following the advice of many people, an auto-mechanic buddy, and forums, this is what I have done, not necessarily in this order

Fuel System -
completely drained the port fuel tank (there was a lot of water present),
inspected riser tube,
inspected vent hose,
inspected fuel input hose,
ran vacuum into fuel inlet hose,
determined all fuel/air paths to be unobstructed and free of debris,
filled tank with new fuel,
removed anti-syphon valve from prt fuel feed line,
replaced fuel filter/cannister,
disconnected and blew out fuel to fuel-pump line, no obstructions
removed and inspected prt fuel-pump, found no fault,
exchanged prt and strbd fuel-pumps,
disconnected and blew out steel high-pressure fuel-pump to carb line, no obstructions
broke down carb,
replaced screen filter, accelerator pump, valve bearing, all gaskets (in other words a carb rebuild), but found no issues other than corrosion resulting from the water in the bowl chambers
exchanged prt and strbd carbs

Air System -
inspected, cleaned, then exchanged both flame arrestors
attempted a vacuum leak test using an unignited propane torch (no flame, just gas) around all of the air intake carb and manifold gasket joints, yielded no results, but when I tried dumping directly into the carb had no resulting increase in rpm either, so this may be something worth retrying with some ether/starting spray. as the symptom still seems like loss of vacuum to me

Control System -
measured throttle arm displacement and throttle butterfly movement of both engines. When the throttles are pushed forward to 50%, the throttle valves open to exactly the same positions

Ignition System -
replaced spark plugs, gapped to .035", old ones showed evidence of extreme lean fuel,
replaced ignition wires,
inspected rotor, a bit old but comparable to strbd rotor,
exchanged prt and strbd rotors,
exchanged prt and strbd distributer caps,
exchanged prt and strbd rotor position sensors,
exchanged prt and strbd "ignition amplifiers", although I think that what this actually does is replace the points, and control ignition timing and advance the timing as rpm increases,
checked ignition timing, port was 14 DBTDC, strbd was at 10 DBTDC, plenty of spark produced by coil,
adjusted both to 8 DBTDC according to the shop manual, both engines running very 'smoothly",
checked for ignition timing advance with rpm increase, timing advances to 12DBTDC at 2k rpm (if I recall correctly)
exchanged prt and strbd ignition coils,

Engine System -
checked compression on both engines, cold
Strbd cylinders were all 148-150 psi, no leak down test conducted
Prt cylinders were all 148-149 psi, no leak down test conducted
the manual says that the compression pressure of the 4.3l LX engine cylinders should be 180 psi, since both engines are comparable I moved on
Oil level of both engines was between the max and min lines on the dip stick, and had been changed every year

After each addition/change/adjustment, the boat was taken out and no change was observed, other than they both ran a bit smoother (probably the ignition timing adjustment). Starboard still awesome, port still starving for power.

She is out of the water and winterized now. Next spring my plan is to exchange the outdrives. They have been removed and the lube oil changed. Oil was free of filings, water, or any other contaminants. I shoved a borescope up the exhaust path to inspect for flapper obstruction. No obstruction was observed. Still a chance that the flapper/s are obstructing but not disconnected. May have to remove the engine side exhaust from manifold.

I have a couple more ideas, then I'm out. Any help would be appreciated

I have an 88 270 Amberjack with twin 5.7's. I had this exact issue with my starboard engine. Turned out to be the O-ring on the fuel filler cap letting water into the fuel tank. I did many of the same things that you have done. The problem would clear up only to reappear. I chased this issue for two seasons. I did learn that Heet and other water removing fuel additives are not to be used on an openly vented fuel system, such as we have in our boats. I wish you luck and hope that your issue turns out to be as simple as was mine.