2004 fountain twin 496's at 3000 to 4000 rpms = then wot one motor 5200 the other the other 4800 rpm.130 hours any ideas?

well.... first thing i would do is switch the tach signal on the back of both tachs and see if that 400 rpm follows the tach or stays with the motor. fixing the tach is easy if thats all it is. second is just as simple... make sure you actually HAVE full throttle on that side...

once those two things confirmed you can go from there.

ok swicthed tachs samething used a snapon external tack samething.checked the throttle linkage no problem.what am I missing?

so the tachs are ok ( i don't understand your answer) if so and motor really down 400 revs then i guess the next thing is to have the plugs out and compression test and leak it down... maybe simple like a broken valve spring... after that valve covers off and see if you wore a lobe off the cam... maybe have the injectors out and pulse them and see if one has stopped working...

a couple of threads here already about people killing pistons for that suspected cause.

my answer is I still have the same problem.before I started this thread I did to compression check and changed the plugs.How ever I did not do a leak down test due to the compressionwas right on the money.help

Stop driving in circles
Sorry, couldn't resist

My guess is prop differences. I've got one set of props that are always off a couple 100 rpm's in the 3500 rpm range but perfectly even at wot. I've got another set that is perfect at 3500 but off by about 150 at wot. Then I have another set that are perfect throughout the range. Of course, these are the ones I spent the most money on.

thats a good idea. my oringinal bravo 24s were a couple or 300 revs better than the new ones. turned out prev owner had dinged them and had them repaired and turned them into
23 1/2 's so that could easily be the answer...

all ready did that and now running labbed.I am almost ready to give up.help

If you haven't already, switch props to the opposite sides and see if the rpm follows the props (unequal labbing)

Also, check the magnet in the bravo drive port to see if something is going on inside... I had upper gears going, and it wasn't noticable until higher rpms... lot's more drag on that side.
Carder