2008 Honda 75HP EFI outboard challenge

[Alphawater]

My son recently bought a 2008 Hewescraft packaged with 2008 75hp and 8hp Honda EFI outboards from original owner. Son put fuel stabilizer in tank upon purchase when filling tank. Main has about 150 hours on it. Main works great at up to 4000+rpm for about 15 minutes then starts to sputter and lose power - sometimes quits. When put in neutral, the motor works fine using the choke lever at raised rpms. Then we engage the 8hp kicker and it works great ongoing. After main sits for a while, will again run fine for a few minutes. Son took boat to professional marine mechanic shop to check out - they suspected injector problems - found the motor in great clean condition with no corrosion and 230+ compression in all cylinders. Did general service including replacing fuel filters which were in clean condition prior to replacement. Could not get problem to replicate when they placed in test tank and gave it clean bill of health. Took the boat out yesterday afternoon and the same problem occurred. We disconnected the gas line from the kicker per mechanic suggestion to eliminate small possibility of air bubble in line - same problem happened - motor still runs fine when in neutral and we use the choke lever to increase rpms. Help would be appreciated. Thanks.

 

[MattFL]

Try running it off of a small portable tank with a short gas line. If that works fine then start checking the main line for leaks, or maybe the in-tank screen is clogged, etc..