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HELP! What is happening with my new motor?


Bayfisher34

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My new 140 Suzuki has about 8-10 hours on it and I have been following the break in process strictly. Whenever I got to the point where you can go full throttle for up to 5 minutes I noticed a problem. Anytime I am at full throttle it's almost like the motors power is going on and off on and off really quick and rapidly and the whole boat shutters too????? I can go pretty close to full throttle and still have normal operation, it only happens when I'm at full throttle.

Can anybody tell me what might be wrong?

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4 hours ago, Santiago said:

What kind of gas did you put in? If you mixed no ethanol with ethanol gas you could get the problem you are describing

The boat came with about a half tank of gas and then I filled the tank up with ethanol fuel. The previous owner might have had no-ethanol fuel in the tank. After putting a new motor on I burned through half of what was then a full tank (possibly half ethanol half no-ethanol) when someone recommended harshly to use ethanol free. So then I topped it off with ethanol free the last 2 times I've gone out burning about a quarter tank or more each time. So that might have been the problem.

If it was, will everything be ok when I burn through the small amount of ethanol fuel left in the mixture?????

There couldn't have been very much of a mixture at all my last time out and it was still occurring the same as before.

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Check the Suzuki owners manual for the engine's maximum RPM rating. (I'd guess it's between 6000 and 6300) If your engine is exceeding that max rated rpm (over-rev)as you near full throttle, the engine will begin to stop firing on all cylinders in order to drop the RPM into an acceptable range in order to prevent engine damage. This will feel like a misfire and will correct itself as you reduce throttle into an acceptable range. If this over-rev is the problem, you will need to put a different prop with a higher pitch or bigger diameter on the engine in order to obtain near maximum RPM (without exceeding it) at full throttle.

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2 hours ago, FLDXT said:

I agree, Rev limiter or fuel restriction when the engine is asking for more fuel. We need to know what your rpms look like when it happens.

I think it was around 5800, but I'm not really sure so I'll check in a couple days when I go back out on it.

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Bayfisher34. Two things occur to me: If you are near the Suzuki dealer, call and ask them if they can plug their diagnostic computer into your motor to determine if an over-rev(s) has been recorded. Also, most tachometers are made to work with different types of engines. There are normally small switches on the back of the tachometer which are used to "tune" the tachometer to the specific type of engine being monitored. If the switches are not properly set, the tachometer may not be giving an accurate RPM reading.

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On 3/27/2018 at 9:08 AM, Santiago said:

What kind of gas did you put in? If you mixed no ethanol with ethanol gas you could get the problem you are describing

That won't cause an issue at all. Just like mixing different octane rated gas won't cause an issue (unless the engine requires high octane only). Every person I know will mix ethanol/non ethanol at some point. 

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5 hours ago, BradM said:

Almost sounds like a fuel deliver issue. Pumps, pick ups, filters good to go? No cracked or broken fuel lines allowing air in? Primer bulb in good shape?

Yes, sounds like you could have an issue with the Anti-siphon valve on the tank...was this replaced...is the ball going flat at the higher RPM's?

 

dc

 

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