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Ask Dominick Your Own Question
Dominick, Marine Mechanic
Category: Boat
Satisfied Customers: 1009
Experience:  25 Years Experience as Mechanic, 20 Yrs Boat Yard Owner/Mechanic, Factory Certified
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LF250TUR looses rpm at times but other motor is fine. already

Customer Question

LF250TUR looses rpm at times but other motor is fine. already replaced fuel lines from tank to water separator to engine,pulled pick ups out tank and inspected. also replaced both fuel pumps and filters. swaped ecu and ignition coils with other motor. check fuel pressures and had Yamaha tech put scanner on and river tested but no codes even when problem occurs. only way to affect problem when it happens is to cycle key off and back on,then put in gear and accelerate. it will do this 4 to 12 times. then it would run at 4700 for 2 hours with no glitch. is there another module on the engine that would reset itself when key on power?
Submitted: 2 years ago.
Category: Boat
Expert:  Jason replied 2 years ago.
Hello my name is ***** ***** I will be helping you today. When this happens, have you checked for spark to see if it is dropping spark on any of the cylinders? Have you tried running the engine off of another fuel source?
Customer: replied 2 years ago.
Not for loss of spark but on fuel yes. Even had 6 gallon tank and bypassed filter to see if it made a difference but no change. turning engine off and restart makes only change.
Expert:  Jason replied 2 years ago.
Where there any old stored codes in the ECM at all? Every time there is an alarm the ECM will store it, indefinitely, is there any history on it? When did this problem start?
Customer: replied 2 years ago.
idk I will have to get rescanned to get history codes. problem started about 50 hrs ago.
Expert:  Jason replied 2 years ago.
Do you boat in salt or freshwater?
Customer: replied 2 years ago.
Customer: replied 2 years ago.
is there any other module on the engine besides the ecm?
Expert:  Jason replied 2 years ago.
No there isn't. The ECM is the only module on the engine. There are so many different things that can cause that issue. Anything from small amounts of water in the fuel, loose battery cable connection, to a short in the harness that likes to act up every once in a while. I hate to say it but it sounds like the engine is going to have to come of the boat and get run in a test tank just to duplicate the problem Does that make sense?
Customer: replied 2 years ago.
why would turning off the engine then restart put up on plane then one engine starts loosing rpm, and do this process 3 to 7 times then run at 4700 rpm for 2 hours with no problem? no way this is a fuel problem. I think it is electrical.
Expert:  Jason replied 2 years ago.
I'm going to opt out. There isn't any answers for you with this one.
Customer: replied 2 years ago.

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