1993 Yamaha 225 rough running

[<gradyscaper>]

My 93 225 Carb model had been running rough at idle and slight vibration(miss?) as I accel to plane (approx 2K-2.5K). Also occasionally would die out other times just vary in power and "catch" then accel. I had changed seperator and also found that 1 of 2 Fuel Pumps was leaking slightly so changed both. Also changed Priming Bulb. That seemed to help with idle and lessened vibration on accel. and eliminated the dying out on accel.

After about 1 month, accel vibration began again
then had overall less power and vibration (miss?) through speed range. I checked compression on all cylinders (range from 106-118 , I assume that is OK). I also checked spark w/ spark gap tester and it seemed OK on all 6. Plugs looked slightly carboned and slightly wet (fuel / not water). I Changed Plugs. I also checked the Throttle Position Sensor and it was off slghtly at CLosed(5.7V vs. 4.9-5.1 Reccomended in CLymer)so I reset.
After that it ran beteer with good acceleration, but there is still a vibration sound at all speeds (almost sounds mechanical, but not sure how to diagnose?). I assume compression test would show something very wrong with rings /pistons /cyl. wall, but not thing else?

ANy insight on where to go next would be appreciated. I am anovice at this and looking for advice.

Thanks

[<jb123>]

does it vibrate in and out of the water? as in on the trailer with muffs? if you spin the prop shaft does it turn normally ...look for a wobble,could be a prop too.
as far as fuel delivery make sure there are as little breaks in the lines as possible,junctions. have you cleaned the carbs....does the motor run up to at least 5600 rpm`s under load/in the water?

[<gradyscaper>]

Thanks for reply jb123.

I have in water, so didn't run on trailer. I guess I should clarify the vibration as a higher pitched sound as opposed to a stronger vibration like from a damaged prop blade while running. The sound / vibration is present during running out of gear as well as in gear under load.

. I removed drain plugs from bottom of carbs with only clean fuel coming out (ie no gunk). I also think I'll connect a portable tank directly to eliminate lines separator and tank selector valve.
I have not cleaned carbs, but wonder about ideas how to clean in place without complete dissasembly.

Any help is appreciated.

THanks

[<jb123>]

dont be afraid to tear them down and do tear them down as far as possible. myself,i would use one can of cleaner for each carb but they really should soak overnight in a good solution. you may need to replace aluminum washers as they corrode and be careful with the brass jets,screws as they can be brittle. the motor is 11 yrs old....have you ever checked the fuel pumps,good idea to rebuild or replace.i would test them by assuring air flow only one direction by blowing into both sides,one way will flow the other should not allow any passage.
you might also want to check the spark "jump" to ensure your coils are putting out what they should.

[<gradyscaper>]

jb123

I guess I'll take a crack at tearing down the carbs. wish me luck.

I did change both fuel pumps (1 was leaking slightly) and that made an improvement for a while.

I used a spark jump tester I got from autozone & looked like a decent jump (I set for about .050) my normal spark plug gap spec is .040. It was bright daylight so hard to tell other than it was sparking?

Thanks for feedback

[<jb123>]

i didnt mean the plug gap,i would definatley keep that at factory,but there is a tool the you plug in the coil leads to and turn motor over.it will make the spark jump at least a quarter inch. your problem sounds to me more like a carb issue tho.

[<gradyscaper>]

The spark tester I used was the type you connect to one plug wre and ground with a screw adjustment for gap. T had minimal directions and the only calibration scale it has is for normal and electronic ignition. You mentioned I should be able to get a 1/4 inch jump, I adjusted for .050, I'm not sure I would have got a spark to jump 1/4". I'll try again to see . If I cannot get that much do you think that is a problem?

Also I removed and cleaned jets and they were in good shape. O Rings good, no varnish.

[<jb123>]

1 more check for you... run the motor at night,try to expose all coils,etc on the back and look for errant spark bleeding.

[<gradyscaper>]

I'll give that a try.
What about the spark jump on the tester, how far should I get it to jup? You said a 1/4". Is that how far I should set the gap on the tester?

I also was wondering about going to a hotter plug since I have seen slightly wet and carboned plugs on all cylinders equally (not enough carbon to bridge , but they are black and somewhat moist with fuel/oil). The spec calls for a 9 and I was thinking of trying an 8 ?

[<gradyscaper>]

I also had a quastion on timing adjustment. The Clymer book I have isn't clear to me on setting timing. It talks about only a static setting with a Dial Indicator checking Stroke of Piston against the X Deg BTDC, but can't see what to adjust. I see the "Pointer" that points to the scale on the flywheel, but it doesn't look like moving that would do anything. I also identified the Crank position sensor, but it looks like that is fixed and wouldn, effect the pointers position relative to the flywheel. Any insight?

Thanks

[<jb123>]

i myself would not change to a hotter plug but a tech might tell you different, i would never want to chance a powerhead failure. i have been running different yamahas for the last 15 yrs and have never had to adjust timing, not saying that it might be out tho,hopefully one of the more experienced people here will help you out.

[<jb123>]

check the manual here :

www.yamaha-motor.com