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Jason, Marine Mechanic
Category: Boat
Satisfied Customers: 14165
Experience:  Degree in Marine Technology. Gas and diesel marine mechanic.
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I have a yamaha 150 xtrb 2 cycle outboard that will only run

Customer Question

i have a yamaha 150 xtrb 2 cycle outboard that will only run to 2500 rpm and intermittingly will go full throttle all filrers and fuel are clean just started yesterday
Submitted: 2 months ago.
Category: Boat
Expert:  Jason replied 2 months ago.

Hello my name is ***** ***** am I speaking with?

When it goes to full throttle, does it just sort of kick in, just like that?

Customer: replied 2 months ago.
this is terry at tsmithfive the answer to your question is yes then it will run a minute or two and falll back to 2600 hundred. you can push throttle forward but it actually slows down cause your just loading it up
Customer: replied 2 months ago.
it is carb motor
Expert:  Jason replied 2 months ago.

Hi Terry

Are you able to check for spark to see if spark is dropping on a bank when running the motor?

Customer: replied 2 months ago.
i wuould think i would have to put boat in water as not to over rev gonna need back pressure. i only live 2 blocks from boat launch. Could do it on the trailer or take it out in the lake. Should I take each plug out and ground each plug against the block on one bank or is there an easier way?
Expert:  Jason replied 2 months ago.

The easiest way to do it is to get a timing light. Pull the engine cover off, run the engine until you can duplicate the problem. Then hook up a timing light to each plug wire one at a time and see if the timing light flashes or not. If it does, there is spark, if it does not, there is no spark. Let me know what happens.

Customer: replied 2 months ago.
If I run it in the driveway the engine will rev up over 2600 with no load on it so probably only one bank. So do I do it in the driveway and just look for fire on one bank.
Expert:  Jason replied 2 months ago.

You want to put the boat in the water, running the engine over idle when on the garden hose is bad for the engine.

Expert:  Jason replied 2 months ago.

That being said you can definitely check it at idle when on the garden hose, but if it does show spark on all 6, you would want to double check it by running it in the water next.

Customer: replied 2 months ago.
ok finally got a few minutes to play with it. in driveway checked for fire upper and lower cylinder appear to have no fire. ok lets do a comp test do that its all good. start checking for fire again now all cylinders have fire wt hell. ok you tell me whats next intermittent fire i can put in water but i dont trust it for any distance. did i mention right before this happened i slammed a wake hard from passin boat. im thinking module going out. help
Customer: replied 2 months ago.
on right bank there was no fire
Expert:  Jason replied 2 months ago.

Got it Terry,

next step is to disconnect the charge coil from the CDI box. Get a volt meter and set it to AC, and measure the voltage on the red and brown wires, and then on the black/red and blue wires and let me know what you get. To measure voltage, have a helper crank the engine over while you are checking voltages at the plug. Is this something you can do?

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