Fouling plugs - 225 txrr

[erniefish]

my neighbor just acquired this motor , low hours , ran good for the first few hours , now fouls plugs , change plugs , runs fine , previous owner said he had a problem . ( gave the motor to him . Motor will sputter , and if patient , after multiple attempts get past 2000rpms , motor is fine . He thinks carbs , I doubt that , that motor has enrichment feature , could that be dumping extra fuel at low rpm ? I did notice that carbs have been into multiple times , manual kinda lists this motor as a "special " monster , whereas settings on this motor are different from any other similar motor . Any thoughts or ideas would be appreciated , thanks

[pstephens46]

Carbs? Always carbs....why fight it?

[rodbolt17]

whuuut????
whut kinda manual ya got that says that?
and here again, this is why model numbers matter.
the enrichment system can be turned off for testing.
just fix the fuel system and go play.\

[bigdummy]

Hello all- new to this site, Thanks for having me onboard.
I am the owner of the motor that is having problems. Erniefish was kind enough to post the problem to try to help me resolve this problem.

This is my first Yamaha outboard motor. Plate on bracket lists the following 225 TXRR
6K7 UL 752652

I have the Factory Service manual (online version,printed version due in this week).

The motor fouls plugs easily and excessively at low speeds. Any speed under 2000 rpm the motor sounds as if it is only running on 4 cylinders (labored when going through no-wake zones, doesn't have a clean, crisp idle in neutral, shaking/vibrating). Above 2000 motor seems to run fine, however it takes patience to get throttled up after just a few minutes of idle time.

I made an attempt at cleaning/adjusting the carbs without success so I am looking for advice, suggestions and guidance.

The manual gives float height, I'm guessing this reading is done with the rubber gasket in place? Also, I had two floats that seemed out of adjustment, but I switched them around and got completely different readings- is everything a matched "set" that needs to go back to the same location each time or can the needle, float, and seat be interchanged at will?

The needle valve tips looked ok to me (under a magnifying glass), but should the needle valves be replaced as a normal carb rebuild?

Regarding the enrichment valve- when I engage the switch on the dash with the engine running, I don't hear the normal "bogging" associated with choking a running engine making me wonder if the vale is somehow stuck open causing a rich running situation.

Thanks again to everyone for the help, insight and knowledge

[99yam40]

does this motor have a choke or an enrichment system
parts breakdown is too fuzzy to see much

Free motor with problems can get expensive

easy enough to look to see if anything is happening to the choke on the carbs if it has a choke, when you hit the switch.

also looking at the choke butterflies to see if they are stuck closed

[bigdummy]

Enrichment system. Took hoses off to see if it was pumping fuel. Pumped fuel until motor started then stopped pumping. I'm guessing this is normal.

Today did a quick check/clean of floats and put boat back in water and ran fine at all speeds for hour, even at idle, then while in no wake zone I could hear it start to load up (sounds like it not running on all cylinders. Now it will only turn 4900-5000, had 5700 before.

Interestingly and probably coincidental, but I had ring free in the tank, got gas at the beginning of the no wake zone but did not add ring free and problem started at the end of the no wake zone (approximately one mile)

[rodbolt17]

did you test the fuel pumps?
did you test the A&B enrichment valves?
and if you clean the carbs at breakfast, get trash in them again at lunch.
guess what is for dinner?

[bigdummy]

Rodbolt,
I have rebuilt both fuel pumps. have not checked enrichment system as it was checked and "re-built" by mechanic just before I received the motor (obviously he didn't get engine fixed so who knows)

I have motor idling "pretty" well but doesn't sound sharp and crisp to me- almost like it labors. Runs fine, doesn't quit or stall, just doesn't sound like it idles "free and easy". I did bump the rpm up to close to 800 in neutral but didn't seem to make a difference. Laboring sound/feeling goes away once I bump up to about 1800 ( I can hear a significant difference)

I have completed following which have had positive effects

replaced top left coil (#1 cylinder?)- motor felt as if it would occasionally lose a cylinder, finally did and found bad coil. Ohm'd all as shown in manual, all checked to spec however I guess this one would die under load. Opposite coil also seems weak (when I pull plug wire at idle I don't notice a big difference). Do these coils typically go bad in pairs?

Checked recirculating check valves- all were bad. Replaced all and low speed/idle smoking is greatly reduced and fouling seems to have subsided. New plugs installed (again) when recirc valves were replaced

Another quick question, where are the carbs normally fouled? Fuel system is new (tank, hoses, filter, primer ) and I've only bought ethanol free gas from reputable locations (not that means anything), Racor has remained clear and free of debris in the ten hours its been used

Any insight or thoughts would be greatly appreciated.

Thanks

[bigdummy]

Realize this is getting to be an old thread, but I can't seem to figure out how to start a new one.
Same motor, replaced a second col which seems to have corrected the occasional loss of a cylinder (at least what I perceived as a loss of a cylinder)

As stated before, motor runs fine at upper rpm, still sounds like it "labors' at lower rpm. What I have noticed is once the motor reaches 4000 rpm it immediately jumps to life . When running 3500 and easing throttle up it seems to struggle to gain rpm, once it reaches 4000 complete sound of motor changes and it is much more responsive throughout the range from 4000 to 5700, back off to under 4000 and motor isn't nearly as responsive.

Today's question- does Yamaha's electrical system have different winding/etc at the rpm ranges or does this still sound fuel related? As I've said before this is my first Yamaha outboard. I've owned several Mercury v-200 and these symptoms were usually electrical problems (stator frequently).

Thanks again to everyone for your help and patience.

[rodbolt17]

yes your system uses a high and low speed charge coil.
no yo0u can hit the choke all you wish and nothing happens.
it is all automatic.
you should have 3 fuel pumps, two supply fuel to the carbs the other takes fuel from the top bowl and feeds the enrichment system.
if the coolent temp does not come up the enrichment stays on.
it also has a crank position sensor, lose that and you lose 2 cylinders.

[bigdummy]

Coolant temp comes up ( I have aftermarket Sierra gauges with temp sender plumbed into the right bank-when viewed from back of boat) to "normal" range -middle of gauge range- so assuming enrichment valve isn't staying on

Where is third fuel pump located? The two I rebuilt are located above oil pump- is the third a similar style diaphragm and location?

Would crank position sensor only cause problem at lower rpm?

Do high speed coils energize at 4000 rpm? Today I was trying to pinpoint fluctuation- I noticed at 4000 (by aftermarket Sierra tach) a 50 rpm difference up or down would make a noticeable difference in the motor responsiveness (3900-3950 and it would slowly respond to throttle position, at 4050 and it would immediately respond to small throttle adjustments). Maybe I'm overthinking this.

All the help and insight is truly appreciated