V/P osxi-G 5.7 lack or power and 1 beep every 5-7 seconds

[2009 stingray]

hey all, i got a bugger hear, took over this job after the owner felt their mechanic was just throwing parts at this problem, . no scanners, no fuel pressure gauges just flying by the seat of their pants.
anyways, after replacing the impeller, then the entire raw waterpump assy, then the manifolds/risers the alarm kept sounding. then it stopped running all together, so they sold the client on a new fuel pump, again, no gauges, new fuel pump in and now no fuel getting to the pump, mechanic says possible blockage in the fuel delivery, the mechanic hooks up a seperate tank and the boat runs fine, mechanic says fuel supply tube or anti siphon valve, which is strange cause the boat has twin engines and the other engine runs fine.

enter me, i back trace the fuel lines and i get to a fuel manifold with 2 3 way valves, one for each engine, i disconnect the lines and find that the valve for the trouble engine is blocked, the only way for fuel to flow is to turn the valve partially in between 2 options, so handle facing right feeds from right tank, handle facing left feed from left tank, handle facing down feeds from both tanks, on this valve, you have to put the handle in between down and right to get flow.
i took the valve apart and found the internals not lining up properly. i reassembled the valve and it worked fine.
engine ran fine although a bit of a miss, nothing significant but i felt it, i did a cylinder balance test and all cylinders were responding. i plan to go back and do a full compression test but for now i replaced the cap/rotor due to corrosion but it did little to help the rough idle.

anyways the customer was out on the boat tonight and the engine in question started acting up. sluggish and no power and the beep, ah yes the beep.
1 beep every 5-7 seconds. all gauges on dash read ok, nothing out of the ordinary. they limped the boat back to the dock and here she sits. .

i'm thinking it may be the sensors on the risers but when i ran the boat, no beeps, no codes, so ill be back to check further but id like to have something to go with.

 

[alldodge]

One or more of the sensors is not reading correctly. You will most likely need a scanner to get close. Can take a voltmeter and measure the 5V supply on the MAP or TPS to see if it's exactly 5V

 

[2009 stingray]

update: took the boat out with the intentions of verifying the false alert then replacing the riser sensors on the fly, verifying repair, well, that didnt play out like expected. since this is a larger boat with no access to the engines while underway, the prior mechanic never verified the 1st issue/repair of the overheat and bad raw waterpump. so while out on the water, the alarm went off, i verified on my scanner the ect reading 190 degrees, we stopped the boat and opened the engine bay, i noticed it was rather wet, i thought maybe the water was getting in from the hatch port hole i had my scanner wire coming through. so i installed the new riser sensors and was skeptical cause the starboard riser was in fact quite hot ( i had forgotten to bring my rf temp gun with me ) then i told the captain to start the engine and give it some throttle, and holy crap, water spraying all over the belt, fuel pumps, generator etc. further deep dive found the water hose from pump to thermostat housing was sliced and leaking under load.
i believe this was the problem if not from get go, definitely some point between needing an entire raw waterpump to circulator pump and manifold/riser replacement.
so we limped back to the dock and i pulled the hose, sure enough, 2 gouges in the hose, looks like it was rubbing on a sharp edge of the engine block, just below the head. also found that the support leg for the raw waterpump was not put back in place and one bolt was missing that goes into the block. wich then allowed the pump to sit freely and the only thing holding it in position was the 2 hoses.
i watched as the engine was started and the pump & hose bounces/shifted/rubbed against the block,

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moral of the story, ALWAYS VERIFY ALL YOUR REPAIRS BEFORE MOVING ONTO THE NEXT PHASE OF WORK.
instead of throwing parts at a problem, verify all the obvious. take the time to really look over the area.
is it wet?
is it really overheating?
is the engine running better or worse than the scanner is telling you?