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Ask K. Kergan Your Own Question
K. Kergan
K. Kergan, Marine Mechanic
Category: Boat
Satisfied Customers: 1030
Experience:  24 yrs exp. Inboard/Outboard mechanic Mercury/ Mercruiser, Volvo Penta and OMC, Johnson/Evin.
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When engine is started, it does not idle smoothly, it speeds

Customer Question

When engine is started, it does not idle smoothly, it speeds up then slows down. Also, when going from neutral to forward gear, the engine either stalls or hesitates. The engine is a 150hp 4 cylinder 4 cycle Yamaha.
Submitted: 1 month ago.
Category: Boat
Expert:  Jason replied 1 month ago.

Hi James, my name is Jason.

I read what you wrote. What is the history on this engine, have you ever personally seen it run correctly?

Expert:  Jason replied 1 month ago.

Are you still with me?

Customer: replied 1 month ago.
Customer: replied 1 month ago.
I have seen the engine run correctly
Customer: replied 1 month ago.
I have seen the engine run correctly
Expert:  Jason replied 1 month ago.

Is there a history on the engine, when did it last run correctly? How old is the fuel itself?

Customer: replied 1 month ago.
The fuel has been purchased recently at a reliable gas station.
Expert:  Jason replied 1 month ago.

So there is no history on the engine?

Expert:  Jason replied 1 month ago.

Have you done any troubleshooting on your own yet, or spoken with anybody else about the problem? If yes, what have you done so far?

Expert:  Jason replied 1 month ago.

You paid the website to speak with me, you have not asked any kind of questions, did you have any questions for me?

Customer: replied 1 month ago.
I purchased the engine new. Had no problems until lately with the hesitation when going forward. Changed gas filters on the engine and on the boat.
Expert:  Jason replied 1 month ago.

I don't know what you have for tools or abilities. But the engine requires a compression tester, spark checking tool or timing light, fuel pressure gauge, and a scan tool to work on. Are you looking to work on this yourself or something else? You have not asked my any kinds of questions so I don't know what you are looking to do here.

Customer: replied 1 month ago.
I have the abilities and tools to do the work myself. MY original question was the engine hesitates when going forward and does not idle properly. What are the possible causes. Be specific. I never heard of a "scan tool"
Expert:  Jason replied 1 month ago.

You are not going to be able to fix this without going to the dealer. Did you want to continue knowing that, or call it quits?

Customer: replied 1 month ago.
Jason, you haven't given me any possible causes yet. What makes you think that I can not fix these problems without going to a dealer. Let's continue. The whole reason that I contacted you was not go to a dealer. If I was going to a dealer, why would I contact you in the first place.
Expert:  Jason replied 1 month ago.

What makes you think that I can not fix these problems without going to a dealer

Because a scan tool is needed to work on these engines, and you don't even know what one is. I'm going to call this quits as I don't see this working for either one of us.

Customer: replied 1 month ago.
You haven't given any possible causes. In your experience, have has caused these problems.
Expert:  K. Kergan replied 1 month ago.

Hi, my name is Kerry

These engines have a number of sensors, you would need a scan tool to determine if one is at fault.

Here is a link to a scan tool, you will also need a laptop.

http://www.ebay.ca/itm/Yamaha-Outboard-Jet-Boat-WaveRunner-YDS-Diagnostic-cable-set-Plug-play-/330918278833

You can do a couple tests without the scan tool, you can check the spark and the compression.

This could be caused by a faulty sensor, poor compression on one or more cylinders, a faulty injector or an ignition problem.

I would rule out the spark and compression first, if both are good, the scan tool is less expensive than an hour of shop labor.

Here is a link to parts diagrams.

http://www.boats.net/parts/search/Yamaha/Outboard/2004/F150TXRC/parts.html

Hope this helps.

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