OX66 or not?

[bucky]

At the risk of sounding stupid...
I've got a '99 (manufactured '98) 175 Yamaha SaltWater Series II on a 21SE. I have a problem where she sneezes and wants to cut out at idle, and also an occaisional issue where the RPMs drop when running hard. This last has occurred twice, both times in a rough sea. Compression is lower (87) in one cylinder than in the others (all between 112 - 118). So I probably have several problems to resolve.

I'd like to perform more analysis and maintenence based on some of the other threads I've read on this site, but I can't come to a conclusion on one question. Do I own an OX66 or not? I'm pretty confident that it's not an HPDI. It's carbed. To begin, I will preform Dunk's decarb in the spring, but spraying directly into the carbs versus the aux tank method seems to depend on OX66 or not. I'd like to clean the VST, but I don't think I've got one.

Hate to sound dumb about it, but until I can figure out exactly what I have, I can't proceed with determining the root cause of these issues. I want to get to a point where I can make a decision to rebuild, repower, or just run her until she breaks.

Model S175TXRX.

If you know what engine type this is, can you also tell me how you know?

Thanks much.

 

[Bryan 2530]

If its carbed, clean and rebuild them.

 

[John_Madison CT]

If it's an Ox66, then there is some simple and basic maintenance to do. Most problems are fixed with these problems:

1. VST filter
2. Low Pressure Fuel Pumps
3. Clean O2 sensor.


The loss in RPM's is probably from a clogged VST filter. But it can have another source. Good luck.

John

 

[miky2884]

If its a 99 it's Most likely an ox66 motor. Look up online a diagram of the motor you can see where the 02 sensor would be on the starboard side of the motor towards the top of the block, this could also be your problem a dirty 02 sensor will cause the symptoms you are having as well.

 

[Brent]

if you need an owners manual go to
http://www.yamahaoutboards.com/owner-re ... rs-manuals

 

[Bryan 2530]

It's carbed.

= no ox66

 

[Megabyte]

Give Andy at Shipyard Island Marine (SIM) a call.
They can tell you exactly what you have, and they can probably give you some diagnosis as well.

http://www.simyamaha.com/category_s/1188.htm

 

[miky2884]

My bad I didn't read that you stated it was carbed.

 

[TimC2520]

Are you sure it's carbed?
I have an S225TXRX, manufactured in '98, model year '99. EFI

Didn't know Yam made both that year. :?:

Any pics of the cowl off?

 

[Megabyte]

There was an overlap period when Yamaha sold both carbed and EFI motors.
I have a 1997 OX66 that is EFI but I believe they also sold carbed motors that year as well.
Not sure when they went all EFI.

 

[Brent]

I dont think you have an OX66
see
http://www.maxrules.com/fixyamahamodels.html

 

[Brent]

Andy at SIM has a better one

http://www.simyamaha.com/Model_Code_Ref ... s/1798.htm

also it is attached

 

[bucky]

Thanks for all of your replies and that chart. Now I know for sure it's not OX66 or an HPDI.

The engine is carbed for sure. Fogged it just this past weekend.

I will contact Andy/SIM as suggested. Seems like a good place to start.

Regards.

 

[gw204]

OX66 fuel injection came out on the 225/250 several years before the 150/175/200. 1997 vs. 2000 if I'm not mistaken.

First thing I would do is pull the head and have a look at the piston and cylinder walls.

 

[miky2884]

Just curious why would you have him pull the head? I guess because he stated he has one cylinder down on pressure.
I would start with Carbs as mentioned most likely your problem.

 

[Megabyte]

Just curious why would you have him pull the head? I guess because he stated he has one cylinder down on pressure.

If one cylinder tests low on compression, there is definitely something going on.
Could be something as simple as a stuck ring due to carbon build-up.
Better to fix it now, than to have it self destruct later. (IMHO)

 

[bucky]

I'm assuming that I do have a cylinder problem. When I had a trolling motor installed, I had the Yamaha mechanic check out the main. He was the 1st to report the one cylinder with lower compression. He said that aluminum transfer was occurring on the cylinder wall and that once started it would continue until she blows. Said that it probably started as the result of the carb being tuned too lean. So I ran my own compression tests and it confirmed his numbers.

I plan to run a Dunk's decarb on it 1st thing in the Spring and hope for some improved compression, but that's just being hopeful. I think what I'll need to ultimately determine is if rebuilding is a viable and long term solution for this motor.

 

[gw204]

That alumimum is your piston coming apart.

If you address it now, you might be able to get away with replacing the piston, cleaning the aluminum from the cylinder walls and correcting the lean condition. If you continue to run it, it WILL come apart and you can count on that happening at the most inconvenient time.

 

[Bryan 2530]

He was the 1st to report the one cylinder with lower compression. He said that aluminum transfer was occurring on the cylinder wall and that once started it would continue until she blows.
.

Stop right there, if this is true your done.

Don't waste your time and or money on a de-carb.

Fix the real problem.

 

[bucky]

I will contact the guy that originally diagnosed it, and price the rebuild and then shop it around some (unless anyone has a recommendation on a Yamaha tech up this way - Northern NJ).

Thanks for all of your comments and suggestions.