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Jason, Marine Mechanic
Category: Boat
Satisfied Customers: 15919
Experience:  Degree in Marine Technology. Gas and diesel marine mechanic.
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Engines Yamaha 300 HPDI Z300 TXRD 6DO X. 1002187 N Z300TXRC

Customer Question

Engines Yamaha 300 HPDI
6DO X.(###) ###-####N
6DO X(###) ###-####P
6DO U (###) ###-####N
Start engines temp bars start flashing and stay flashing all the time
Starboard engine will not exceed 1900-2000 rpm when powered up on it's own
It will rev up in neutral or under power with other engines
Hooked up analyzer no codes shown Done
Boat ran good at 3600 rpm…ran it up to 4600 and it ran good….ran at wot and the stb engine started cutting out and goes into guardian
Let sit for 10 minutes ran fine
Tested boat again and both stb and port engines went into guardian mode at wot
flushing the engine and cleaning the poppet valve
water jacket gaskets and head gaskets Done
flush the lower unit Done
Fuel cleaned Done
Replaced spark plugs and water filters Done
Submitted: 10 months ago.
Category: Boat
Expert:  Jason replied 10 months ago.

Hi Gordon, my name is Jason.

Are you working on the engine yourself or is somebody working on this for you and relaying the information to you? Which analyzer is being used specifically?

Customer: replied 10 months ago.
The boat is at Marine Max in Sarasota, they have a certified Yamaha tech, I did not ask what analyzer they used, I assumed it is a Yamaha unit.
Expert:  Jason replied 10 months ago.

If you are not working on this yourself what kinds of questions did you have for me? How is it I can help you?

Customer: replied 10 months ago.
Marine max is suggesting pulling the engines apart which does not make sense to me. The engine that does not rev up unless in neutral or with assistance of other engines does not to me require engine rebuild, the flash temp bard is not engine rebuild, the port and stb engines both going into safe mode does not to me need engine rebuild. To me their is an issue that someone must have had before. I am looking for someone that knows these engines and can think through the problem and suggest a fix
Customer: replied 10 months ago.
Also pleasure to meet you via this comm
Expert:  Jason replied 10 months ago.

I agree, this is an electrical or fuel problem, not a mechanical problem. Here is the 1000 dollar question. The temperature light is flashing/going off. If the scan tool/analyzer is hooked up to the engine. What does the temperature say according to the scan tool? Does the scan tool say the engine is hot, or does it say the engine is running a normal temperature (160F or so)

Customer: replied 10 months ago.
My understanding is that it says the engine is running normal
Expert:  Jason replied 10 months ago.

Is that normal according to the scan tool or according to something else?

Customer: replied 10 months ago.
They used an temp gun to look at the engine temp when it was running and they all ran within the temperature limits
Expert:  Jason replied 10 months ago.

The engine has a temperature sensor and that sensor tells the engines computer what the engine temp is. In turn, the engines computer tells the gauge what it should be showing for a measurement. So what's important here is what the engines computer "thinks" the temperature is. The way that's done is by hooking up the scan tool to it and seeing what that temperature is reading in the scan tool. Whatever the scan tool says for a temperature is what the engines computer thinks the temperature is. This needs to be done when the temp light is actually flashing, and not when it's behaving properly. If the engines temp sensor is bad, or if there is a short in the wiring between the temp sensor and the engines computer that can make the engines computer "think" it's hot when it's really not. Does that all make sense.

Expert:  Jason replied 10 months ago.

Do you have any further questions for me on the issue?

Customer: replied 10 months ago.
That does make sense, it does not make sense that all three gauges are flashing unless there is one central controller
Customer: replied 10 months ago.
the starboard engine not rev up question
Customer: replied 10 months ago.
Why would everything be ok until the motors are run at wide open, the engines do not go into safe mode when run at lower rpm

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