Yamaha SX250TXRA losing RPM

[tbwadsworthjr]

I can finally solve a problem first posted here about 2 years ago. The starboard engine of a new pair of Y. 250txra's would drop 3 or 400 rpm as it neared top end; around 4700 to 4800 rpm it would drop back to 43 or 4400. A new ignition switch, new wiring harnesses, fuel hoses, filters etcetc and many many hours (and$)of diagnosing later, the problem is solved - an oxygen sensor. This was a problem from the fresh out of the box starting position. Engines have about 10 or so hours running and about 4 or 5 times that testing and trouble shooting; runs like a top now. 56, 57, 5800 just fine. Boat is a Mako 28, 1990 model 285.<br />I would think that two dealers and Yamaha Atlanta could solve a simple problem like this fairly easily. Not so. Oh, a five year warranty on them also.<br />Any guidance on how to value a 'split' boat like this would be appreciated - 1990 boat, 2003 / new motors. Time to get out.<br />If you have a mysterious problem that sounds like fuel or electrical, try an oxygen sensor.

 

[rodbolt]

Re: Yamaha SX250TXRA losing RPM

coulda tole ya that and a lot more to check. problem is we are runninng low on technicians that can actually trouble shoot.<br /> I just did an F225, complaint was stbd 5100 port 5300. other than low RPM no issues.<br /> previous techs had done all the laptop testing. took me 15 min to find a bad spark plug in #5 cyl .,<br /> computer diagnostics are great. however all it usually tells me is whats not broke. same using the winky blinky on your 250. would have told ya real quick what was not wrong.<br />one of the first indications of a bad O2 sensors is sluggish or no RPM musch past 4K. push it and youll replace #1 piston as well.<br /> seems the ECU is not smart enough to know its lean and makes it even leaner.<br /> the 8.1 volvo two weeks ago had been in two shops, I found the #8 plug wire off.<br />idled fine except a bit of noise from the jackshaft, that was my first clue.<br />same as the F225, it had a clucth chatter noise at a dead idle in gear.<br />as a tech ya not only have to use your test equipmentand brain but your eyes and ears and even your nose sometimes.

 

[Ray Neudecker]

Re: Yamaha SX250TXRA losing RPM

Exactly why sometimes it is hard to give the instant answers some people seem to expect over the internet. So many times a visual inspection or listening to the engine run can be so important in diagnosing. I don't know how many times I have fixed bad CDI's with a battery charger when I first heard the motor turn over. They had already been diagnosed and condemned by other techs.