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Thread: Optimal RPM range for Yamaha 30 HP 2 stroke

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    Default Optimal RPM range for Yamaha 30 HP 2 stroke

    I recently purchased a used Yamaha 30 HP and after a number of boat mods and adding a Tiny Tach finally got it on the water to see what kind of RPM's I'm getting. This thing is running around 9000 RPM at WOT. What is the ideal range for this motor? I don't have the manual. Am I under-propped?

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    What rpm are you seeing at idle? More than likely your setting is not correct on the tiny tach. I have tried 2 different brands of them, now they are sitting in my tool box. If you have a 2 cylinder you MIGHT get it to work but if you have a 3 cylinder do yourself a favor and buy you a marine tach either analog or digital. I did the same thing and now I own a yamaha digital and saved myself a lot of headache and it works perfect.

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    Hadn't really considered that it might be the tach. I'll run it on the hose tomorrow and get back to you on the idle RPM's.

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    What yamaha digital?

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    The one I bought was Pt # 6Y5-8350T-83-00. There are others that will work but this is the one I have.

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    Somethings not right. Most smaller 2 strokes should be around 5500-6000 rpm at WOT .
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    I have the same motor and was wondering the same. Yamaha claims that it makes it's 30hp @ 5000 rpm. I was planning on using 40hp carbs, but now I'm going to bore out the factory set. It should be fun trying to get the jetting dialed in.

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    Tiny Tachs are notorious for giving incorrect readings, mostly because the tach is not set up correctly. Check and see if yours has settings for 2-4 stroke, number of cylinders, etc, before giving up.

    Not to say there is not something wrong with the tach, as there are many complaints about them on this and other forums, but any tach unless set up for a specific engine needs to be set correctly so as to work correctly. I have heard also that how you run the PU wire can affect them as well as how it is placed around the plug wire and how close to the plug.

    You might also Google "Tiny Tach Problems" and see if anyone else if having the same problems you are.

    Good Luck

    ADD:

    9000 RPM sounds like about 2 times what the motor should be turning so it is another tip the tach is set up wrong for the motor and 2-4 stroke.

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    Sorry for the delay. So, it appears that the TT was on the wrong setting as my idle RPM's were running about 2050. Problem now is I'm not sure what setting is the correct one. The TT has settings for SP ARK PER REVOLUTION. If it's a 3-cylinder motor, do I need to have it on 3P1r or 3 sparks per revolution? Or is it based on 2-stroke and therefore 2P1r? If someone knows what the idle RPM's should be, that would help me as well.

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    [QUOTE=Mallards Only;146947]Sorry for the delay. So, it appears that the TT was on the wrong setting as my idle RPM's were running about 2050. Problem now is I'm not sure what setting is the correct one. The TT has settings for SP ARK PER REVOLUTION. If it's a 3-cylinder motor, do I need to have it on 3P1r or 3 sparks per revolution? Or is it based on 2-stroke and therefore 2P1r? If someone knows what the idle RPM's should be, that would help me as well.[/Q


    Mallard:

    A two stroke motor fires ONCE each RPM (revolution per minute) for each cylinder. Three cylinders, one firing impulse each revolution per cylinder = 3 firing impulses per revolution for this motor.

    Hope this helps. When you get it (the TT) adjusted correctly you should read 5000-6000 RPM at WOT depending on prop pitch.

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