Yamaha 90 runs rough
 

Got a Yamaha 90hp 97 mod used a few years ago. It runs rough at low end
through mid range. Last two seasons I have taken it to a shop where the
mechanic soaks the carburators. Guy says that it is a mystery to him that it
keeps doing it and says he has never had one act quite like this before. He
has been out on a water test and says it sounds like it is dropping one of
the cylinders. I see on the Yamaha home site that there are carburator
repair kits available. Are there any Yamaha mechanics on here that think a
repair kit for each of the three carburators is going to accomplish any more
than soaking the carbs? Thanks for any advise. NV

I'm not a mechanic but I had a similar problem with the motor on my bass boat.
It turned out to be the carbs but they initially thought it was the stator.
Evidently there are low and high speed windings. I hope this isn't the case
since they are big bucks to replace!

Dan


Nick VanderWal wrote:

Got a Yamaha 90hp 97 mod used a few years ago. It runs rough at low end
through mid range. Last two seasons I have taken it to a shop where the
mechanic soaks the carburators. Guy says that it is a mystery to him that it
keeps doing it and says he has never had one act quite like this before. He
has been out on a water test and says it sounds like it is dropping one of
the cylinders. I see on the Yamaha home site that there are carburator
repair kits available. Are there any Yamaha mechanics on here that think a
repair kit for each of the three carburators is going to accomplish any more
than soaking the carbs? Thanks for any advise. NV

Did it fix the problem when he first soaks the carbs? If so, your problem
is fuel gumming them up. A repair kit is nothing more than gaskets, float,
needle, and maybe seat.

If the soak fixed the problem then chances are you are getting poor gas
and/or letting it sit for too long w/out fuel stabilizer. Try using a
different gas station (name brand) and personally I use 93 octane in my boat
and have never had a problem. No more gas than you burn the 20 cents a
gallon is cheap compared to the agrivation and repair costs.


--
Tony
my boats and cars at http://t.thomas.home.mchsi.com
"Nick VanderWal" wrote in message
...
Got a Yamaha 90hp 97 mod used a few years ago. It runs rough at low end
through mid range. Last two seasons I have taken it to a shop where the
mechanic soaks the carburators. Guy says that it is a mystery to him that
it keeps doing it and says he has never had one act quite like this
before. He has been out on a water test and says it sounds like it is
dropping one of the cylinders. I see on the Yamaha home site that there
are carburator repair kits available. Are there any Yamaha mechanics on
here that think a repair kit for each of the three carburators is going to
accomplish any more than soaking the carbs? Thanks for any advise. NV

Thanks very much for replies. Will get to work on it. NV

"Nick VanderWal" wrote in message
...
Got a Yamaha 90hp 97 mod used a few years ago. It runs rough at low end
through mid range. Last two seasons I have taken it to a shop where the
mechanic soaks the carburators. Guy says that it is a mystery to him that
it keeps doing it and says he has never had one act quite like this
before. He has been out on a water test and says it sounds like it is
dropping one of the cylinders. I see on the Yamaha home site that there
are carburator repair kits available. Are there any Yamaha mechanics on
here that think a repair kit for each of the three carburators is going to
accomplish any more than soaking the carbs? Thanks for any advise. NV

On Mon, 21 Feb 2005 20:03:27 GMT, "Nick VanderWal"
wrote:

Got a Yamaha 90hp 97 mod used a few years ago. It runs rough at low end
through mid range. Last two seasons I have taken it to a shop where the
mechanic soaks the carburators. Guy says that it is a mystery to him that it
keeps doing it and says he has never had one act quite like this before. He
has been out on a water test and says it sounds like it is dropping one of
the cylinders. I see on the Yamaha home site that there are carburator
repair kits available. Are there any Yamaha mechanics on here that think a
repair kit for each of the three carburators is going to accomplish any more
than soaking the carbs? Thanks for any advise. NV

I had three of these hanging off a 19' Baja. A blast to drive out in
the open sea.

What specific tests did the tech perform on this powerhead?

There is a diagnostic procedure for most engines I have worked on and
they usually pinpoint the cause of the problem. This starts with a
basic visual inspection, then moves on down the line to a simple spark,
compression, fuel and other simple tests. If any problems are detected,
then often a teardown of certain parts of the powerhead is required in
order to have a closer inspection.

It almost sounds like this tech didn't do his basic checks. I would
recommend getting a service manual for that powerhead and having a
closer look at other possible causes. And maybe find a new tech. Just
my opinion.