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adunn

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"Have twin 1997 454 EFI engine

"Have twin 1997 454 EFI engines,after 30 to 40 min running the starboard engine start to have RPM fluxuation between 3300 to 1800 and all area in between,like its not getting enouh fuel,it will stall if you dont cut the throttle back, after this engine cool down will run good for the same amount of time. we have change the fuel pumps, both low and high pressure,fuel cooler,anti syphon valves, fuel water seperators,clean fuel and tanks.check ignition,plugs,dist,cap and rotor.we are at or wits end Can anyone help."
 
"When it starts to cut out, sh

"When it starts to cut out, shut it off and remove the fuel filter. I bet it's not full! Mercruiser has a problem with these engines, but there is a fix available. After raising hell with them for two months, they admitted the rpoblem and installed an electric pump ahead of the fuel filter. Since then, no problem."
 
"Tom: Thank you for this infor

"Tom: Thank you for this information,but I do have a low pressure pump on the left side of the engine mounted on the deck in line with the gas lines. My mechanic stated that due to vapor lock on these engines that why they install the additional pump
I have check yhe fuel water seperator on more than one occasion and we did have a full cup."
 
Run a fuel pressure test. Tha

Run a fuel pressure test. That's the easiest way to tell if it is supply related. Are there any DTCs stored?
 
"Rick: Thank you for your sugg

"Rick: Thank you for your suggestion will have the mechanic do so, DTC's None on the computor."
 
It sounds like you have covere

It sounds like you have covered all the mechanical issues. It sounds like you have a heat related problem with the engines ECM. This black box controls all issues with the engine. If its getting to hot it could scramble its little electronic brain. I would next look at the ECM
 
"IIRC, your raw water pumps ar

"IIRC, your raw water pumps are belt driven, right? I would take a look anyway. I would also look at the oil cooler inlet side- maybe that's clogged.

Also, since it hasn't been mentioned yet, check the boat plug for that motor and the point on the block where the ground wires meet. Do a wiggle test with the key ON and see if you hear any clicks or buzzes. I have seen boats with loose wires, terminals, retaining nuts, ring terminals that were never slid onto the stud- you name it.

Which ignition system do you have? The IC module may be having problems, it could be the ECM as Art said, the tach lead may be pinched and shorting to ground, there could be a loose plug to the IC module, etc."
 
"Capt Myers: thank you for you

"Capt Myers: thank you for your suggestion thats the first thing we check when we hook up the computor,but we could of miss a connection. I hope. By the way My mechanic call and mercruiser suggest to swap out the ECM module and see if the problem goes to the port engine.If so then we will replace the module thank you so much for your help.
Jim Thank you I will look at the oil Cooler,I was going to change the impeller this week end,but if it was the raw water cooling eystem,
it would over heat when the engine warm up, ihave check the engine temp with a digital heat gun and the temp on both engine are around 170 to 175.Thank you for your suggestion."
 
"Capt W Myers: Switch ECM from

"Capt W Myers: Switch ECM from the Starboard to the Port and Port to Starboard the boat runs good so far have not had good weather to run for 40min, but will let you know the outcome when I do. Thanks again"
 
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