F225 gone mad!

[Seafari1967]

I have a problem with a F225. It was running well then just lost power, stalled and would not run. When starting (have to use revs to get it to run) there's a lot of "carbon" (black smoke) and then it stalls. A mechanic has done compression test and al cylinders check out fine. Swapped over computer with good engine (twin set up) but no luck. Any ideas?

[99yam40]

black smoke = too much fuel.
check fuel pumps

Might monitor rail fuel pressure to make sure in spec
Could be stuck open injector also

Posting model # may help others know exactly which motor it is

[TownsendsFJR1300]

Besides the above, pull the spark plugs and check for any excesive black (wet/rich) on each one to narrow down if its a single injector or....

[rodbolt17]

two things.
1, have your mechanic swap EVERYTHING one part at a time.
2, find a real mechanic.
use the Yamaha dealer locator function, find a shop with a master tech.

in the time it took your mechanic to swap ECU's I could have diagnosed the problem.

in the time it took your mechanic to run a compression test I could have done a leakdown test,two cigarettes and a cup of coffee.

use that dealer locator.

[Seafari1967]

two things.
1, have your mechanic swap EVERYTHING one part at a time.
2, find a real mechanic.
use the Yamaha dealer locator function, find a shop with a master tech.

in the time it took your mechanic to swap ECU's I could have diagnosed the problem.

in the time it took your mechanic to run a compression test I could have done a leakdown test,two cigarettes and a cup of coffee.

use that dealer locator.

Thanks for the advice. After the authorised Yamaha mechanic did compression tests and checking timing belt etc, the he put it down to electrical (probably faulty MAP sensor) so he started swapping out parts. Luckily with a twin fit out this was possible. Otherwise it would have been near impossible to diagnose through a process of elimination. The last thing was the wiring harness and that was it, a faulty harness, who would have thought? Motor runs like a dream. Now to see if we can find what is wrong with the old harness or order a new one (69J-82590-60-00 YAMAHA WIRE HARNESS ASSY $799.44)

[boscoe99]

What year F225?

Does it have optional water pressure and/or speed sensors installed?

[Seafari1967]

It's 2005 model, no extra sensors other than LH rotation factory fit.

[rodbolt17]

faulty MAP would be seen at key on engine off with the lap top.
please find a real mechanic.

compression test is a waste of time, similar to teats on a boar hog.