[Video] 155 power doesn't change from 3/4 to full throttle.

[DualSportDad]

I have a 2003 sportster 155 with 144 hours on it. I purchased it recently and it ran poorly, I cleaned the injectors and it ran better top speed was 45 mph (gauges don't work no idea rpm). While on the first (really second time out) run testing top speed the intake tube from the air box to the throttle body collapsed and there was all kinds of debris floating around in that tube from the rusted coil that helps it keep it's shape. I have gotten the boat back on water and the boat runs great from 0-50% throttle but from 50-100% especially 75-100% the throttle doesn't respond to the change. I took the boat out today with candoo pro hooked up and the tips sees the throttle change. The other thing I can think it might be is maybe some trash got into the filter inside the actual intake manifold and it's clogged.anyone ever experience this? I should have mentioned, the rpms at full throttle are 6400.

Video link

 

[Rae]

6400 is kinda low but not unreasonable. My 2011 (155hp) topped out at 40-41 with a Solas impeller at 5000' elevation and only hit 6300 rpm at wot. It seemed to have the issue where it didnt change much from 50%-100% throttle but I believe it was because I was air limited.
Did you remove the intake tube that was collapsing or replace it? What elevation are you running in? You said cleaning the injectors helped but have you tried cleaning them again and checking the spray pattern on them make sure they are free? Also, it's possible if they needed cleaning that the fuel line and/tank could have had old gas in it and could cause future clogs or issues.
45 is not a bad speed for a 155, 50 is generally the max for a naturally aspirated 155, so you aren't too far off, especially if you are having issues.
Another thing I've learned with the 4tec rotax engines is of the oil level is too high, the crankshaft could be possibly slapping the oil as it turns which is not catastrophic, but could possibly slow down the rpm enough to effect max speed.

Sorry if I hit you with a lot, but its better than going one by one over many days/weeks.