2017 yamaha 300hp 4stroke stalls on slow acceleration or deceleration

[busman1965]

I have a 2017 300hp Yamaha 4 stroke that runs fine when you nail it hard on acceleration or cut the throttle fast to decelerate, but always seems to cut out when you do either slowly. It seems to happen in the 2000 to 2900 rpm range. No chance of keeping it running once it starts to die. But it will restart instantly once it dies. If I slam the throttle down hard, it accelerates and runs perfectly all the way to full RPM, and will decelerate fine if you chop the throttle fast. I service the engine regularly, new oil and all filters etc. It has about 500 hours on it. Aside from the stalling issue, it runs perfectly and the fuel burn is normal. Engine runs cool and clean as well.

Cant go to a dealer as I am in the Bahamas on a remote island. Thought it was possibly a weak low pressure fuel pump or possibly a TPS? Any thoughts as to what to check? I am a mechanic by trade, but not 100% familiar with the new outboards, but have rebuilt VST systems and such.

 

[99yam40]

I am of no help, but hope someone drops in with good advice

 

[dingbat]

Moving the throttle is common to both situations.

I would check for a flakey shift switch or whatever mechanism they use today. I would also check to see if you didn’t have any loose or chafed wires in the throttle

 

[busman1965]

Ok that is a good idea, hadn't though of that! I will look it over and see.

 

[busman1965]

Ok that is a good idea, hadn't though of that! I will look it over and see.

I looked all of the throttle over underneath as well as under the cowling and dont find any chafing on the wires to the switch for Neutral....hoped it would be something that simple, but I guess not!

 

[busman1965]

I did notice today that it only dies in the 3000 to 3900 rpm range. If I accelerate to 4000+, fast, then it runs like normal. Ditto if I chop the throttle from 4000 to dead low idle, it runs fine. Its definitely in the 3000 to 3900 rpm range that is the trouble spot. Oh, and no loss in power either, it planed out a 25 Whaler loaded with 12 people easily today, just had to be fast on the accel/decel with the throttle.

 

[99yam40]

may be the TPS loosing signal in a spot but ok in others

 

[vroom ZOOM]

I have a 2017 300hp Yamaha 4 stroke that runs fine when you nail it hard on acceleration or cut the throttle fast to decelerate, but always seems to cut out when you do either slowly. It seems to happen in the 2000 to 2900 rpm range. No chance of keeping it running once it starts to die. But it will restart instantly once it dies. If I slam the throttle down hard, it accelerates and runs perfectly all the way to full RPM, and will decelerate fine if you chop the throttle fast. I service the engine regularly, new oil and all filters etc. It has about 500 hours on it. Aside from the stalling issue, it runs perfectly and the fuel burn is normal. Engine runs cool and clean as well.

Cant go to a dealer as I am in the Bahamas on a remote island. Thought it was possibly a weak low pressure fuel pump or possibly a TPS? Any thoughts as to what to check? I am a mechanic by trade, but not 100% familiar with the new outboards, but have rebuilt VST systems and such.

fly by wire or mechanical? Get the YDS software and cable on ebay for cheap, that will tell you a lot.