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TimC2520

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Location
Media, PA and Brigantine. NJ
1999 225 OX66 SWS

Hi Fellas,

May need help with this.....I generally cruise at 4200 RPM's
Coming home Fri afternoon, throttled up to 4200 and it sits there for 5-10 seconds then comes back to 36-3700 where she'll sit for 2-3 seconds...then comes back up to 4200 where it stays for 5-10 seconds....then back down to 36-3700 where she sits again for 2-3 seconds, then back up to 4200.....this process goes on and on and on...same symptons.....I should note, this only happens above 3000 rpm's and the "drop" is always the same (600+- rpms). It sounds good, no cough/sputter etc, no smoke...it's a smooth increase/decrease, almost as if someone is throttling up and down...it's also not a sharp or sudden increase/decrease. Saturday the wind blew so I checked and swapped out the plugs and water seperator filter though all looked clean...Sunday I fished again and had the same problem. I spoke to my mechanic who will HOPEFULLY get a chance to look at it Tuesday or Wednesday. I mentioned to him the possibility of it being the VST screen or a fuel pump issue and he said (again without looking at it yet) that it sounded to him like a coil problem or possibly a spark plug wire(s) being bad and that's where he'll look first. He said if it was a fuel starvation issue it probably would not be recovering so quickly. Any opinions? :?:
 
I've owned a couple of these engines and have read the internet about them for at least 5 years.

The problems line up with a usual pattern:

1. VST filter (yes this can cause all kinds of problem you can't imagine)

2. 02 sensor. (I had to replace mine once as the engine lacked power and the fuel burn went up 50%)

3. Low pressure fuel pumps (regular 3 year maintenance item)

4. TPS sensor. (definetly last but these go at times.)


From all the reading I've done on Yamaha's, coil's and electrical problems seem to be in the minority. If you haven't already, I would post the same question at www.thehulltruth.com



John
 
My 250 OX66 had a similar problem a couple of years ago and it turned out to be the O2 sensor. In my case, cleaning the sensor did not help but a new one cured the problem. If I tried to run in the higher rpm range it would do the surge thing like you are describing, if I backed off the throttle some it would smooth out and run all day that way. Fuel consumption was up also. If you know someone with the same motor that is running good, swap out the sensor and see if that cures it. Good luck.

Here's a link to parts at a good price.

http://www.yamahaoutboardparts.com/
 
John_Madison CT":23sjj2gl said:
2. 02 sensor. (I had to replace mine once as the engine lacked power and the fuel burn went up 50%)

3. Low pressure fuel pumps (regular 3 year maintenance item)
Click to expand...

I had a similar problem with my 1997 225 OX66 two years ago and the O2 sensor and low pressure fuel pumps (3 of them) were the culprits.

Hope you get yours squared away without too much expense.
 
Thanks guys,

I am looking at the shop manual now and I am far from a mechanic.
I don't want to sound sarcastic but these jobs do not look very difficult at all? Am I missing something? The fuel pumps look like nothing more than $35+- a pump X 3 plus a new gasket for each. Cut the plastic cable ties mine has holding on the hoses (in and out hoses), remove two bolts, remove pump, install new gaskets on new pumps, insert 2 screws and re-attach new pump...check for leaks? Parts #36 and #50 in the below diagram..Is that it?

FUEL PUMPS
http://www.boats.net/parts/search/Yamah ... ndex.html#



O2 Sensor looks like a wee bit more involved than replacing a spark plug?

Cut plastic clamp holding sensor wire harness on rubber boot. Pull rubber boot off. Trace sensor wire harness to the connection in the engine wire harness and remove plastic clamp at enhgine temp sensor harness. Romove 2 screws from cover and pull cover away. Remove sensor harness. Remove 3 bolts and remove mounting block and discard gasket.
This is where it gets confusing..It says to pull metal draw tube from cylinder block opening and replace if possible because the new draw tube is redesigned to increase sensor life. I do not see a draw tube in the diagram or a part number. Is the draw tube the sensor itself?
Loosen the nut, unthread the sensor, thread nut onto replacement sensor and re-assemble similar to the disassemble with a new gasket....
Part #41 (Sensor) and #46 (gasket) on diagram below...Is that it in a nut shell? I know Murphy's law will certainly show up, but is it that bad?
Also, there is not mention of nut sizes but there are torque specs....

O2 SENSOR
http://www.boats.net/parts/search/Yamah ... ndex.html#


When you guys did these on your own were you happy with the results? How long did it take roughly?


Thanks,

Tim
 
The fuel pumps were simple, but I let my dealer do the 02 sensor. :wink:
 
The O2 sensor is very simple to do. I would loosen the sensor from the mounting block before you remove the block from the engine. I cut a slot in the box end wrench that fits the sensor nut. The slot will allow you to get the sensor wires inside the box end. The plug ends would not fit through the box end.
 
O2 sensor was simple. You will probably need a vise nearby as the 02 sensor is screwed into a cast iron holder with quite a bit of torque. No big deal though, you'll get it.

VST filter, 02 sensor and low pressure pumps are relatively easy jobs.
 
I don't have access unfortunately to a vise at the marina where I keep it and my house is 90 miles away. Can I do as Capt. Bill suggested and loosen sensor from block before removing block?
Also, if anyone is somewhat local to LBI, NJ, I'll compensate you for your time and expertise... :lol: ....just a thought to anyone local who has done this job before.
 
You don't need a vice, just loosen the 22mm O2 sensor nut before you remove the casing from the engine block. You just need to loosen it, don't try to remove it until the casing is off, otherwise you will twist up the sensor wires.

The draw tube is part #49 in the parts diagram, they call it "joint".. once you remove the O2 sensor casing you will see the end of the draw tube protruding a bit from the engine block. Just use a pair of pliers (if the engine is hot) to remove it, it will come right out.

Don't sweat it, both jobs are very straightforward. All the bolts are 10mm, FYI.

Have some 'tools' ready to scrape all the carbon off the draw tube, and make sure the hole through the center is clear. If not, you can use a small drill bit (by hand) to work your way through it. Get as much carbon off the sensor itself as you can, as well as the inside of the casing. I usually take a screwdriver and scrape as much as I can off, then flush it with carb cleaner, etc.. to pick up all the loose stuff.

-- Tom
 
I soaked the draw tube in a little ringfree for a few hours, then was able to scrap the carbon of with ease.
 
If you haven't done it, I highly recommend you clean the VST filter.

Mine was gunked up after 100 hours this season - it was cleaned in the spring.

VST Filter After 100Hrs
1234669422_f5ac3caf38.jpg


Clean VST Filter
1234670654_ec6cfd99a7.jpg


-- Tom
 
How do you guys clean it, I just have been buying new ones. :x
 
Absolutely not.

I actually bought something similar and its useless - there isn't enough clearance around the bolt for that thing-a-ma-bob to fit.

I use a pair of channel-lock pliers.

-- Tom
 
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