Need help with my Yamaha stern drive

[mrdennis64]

I have a 91 Ebtide with a Yamaha 4.3 yems stern drive that my wife purchased new. We have never had any problems until now. The last time out we were cruising along about 3200 rpm when it just slowed down for no apparent reason. Temp, oil pressure ok and charging. Replaced plugs and wires and had carb rebuilt but no change. Starts great and runs up to about 2400 with no problem but above that it misses and back fires. From my research the ecu can put it in safe mode? The temp and oil pressure safety switches seem to check ok. Having trouble finding anyone to work on it since it's so old and parts are not available. Is there a way I can test the ecu or a procedure to reset it? Am I overlooking something? I considered changing to a distributor but was told that causes shifting issues?

 

[Swampmouse2]

Good luck my friend. Not many folks will even look at it. Believe me, I too have learned this the hard way. When the season slows down, Capt. Ken will probably take a look through here. I bet he can tell you.

 

[Bondo]

Starts great and runs up to about 2400 with no problem but above that it misses and back fires.

Ayuh,.... Welcome Aboard,.... Have ya checked the Contents of the fuel filter for water, 'n crud,......

Sounds like it's runnin' outa gas,.....

 

[mrdennis64]

First thing I did was change the fuel water separator filter and cleaned the screen at the carb. The fuel was fresh that day. After the carb rebuild I checked fuel pump volume and ran a line directly into my 5 gal can I use for mowing with no change. Thanks for the response.

 

[Daves70]

I'm just guessing. But I had the same problem with mine.I changed out the distributor to an EST kit. Since then I have come to learn that If your trim position sensor or your trim limit switch are acting up the ecm will think the out drive is up and limits rpm to 2500.There should be a way to test these parts or bypass them.The EST distributor kit fixed the running problem but now my gauges don't work properly as they run through the ecm.Hope this helps. Good luck.

 

[mrdennis64]

Didn't know it had one but that makes sense. I will check it as soon as I find it. Thanks!!

 

[mrdennis64]

Well it was the trim switch causing my problem. It was way out of adjustment indicating the leg was only partially down when it was actually all the way down. Pulled it out but didn't really see a cause. Switch connects to shaft via a splined plastic bushing but it looked ok. Thanks for the responses!!!