I'm having issues with a boat/motor (2009 Skeeter 20i / 250 HPDI Series 2) and struggling to find answers. My boat will hop on pad and run great until about 3500-3800 RPM's. At that point it starts to choke and cough and stall. It stays on pad but struggles until I lower the RPM's. All fuel pumps have been replaced (including the high pressure). All fuel filters and diaphrams have been replaced. Compression is perfect. Lower end unit is great. New spark plugs. New bulb.

I've also had some electrical issues with my touch pad on the dash. I don't think it's related, but who knows.

Your filters replaced included the VST screen? Sounds like a clogged one

Yep. That's what I thought it was too. Those were also changed.

Have you ever changed fuel lines? They could be breaking down and plugging up the fuel flow. 6 years could very well be enough time for the ethanol to eat them up. It doesn't take much resistance or blockage to drop fuel volume down even though you have good pressure and volume at lower RPM's. Also make sure you are getting full spark advance.

I am thinking if it was lean fuel you would have already blown the motor because it sounds like this has been going on for a while. Watch the tack to see if it starts fluctuating. Check the spark at the problem rpms.

Thanks for the advice! The motor was tested with an external tank and ran like a top. The problem seems to be coming from the boat. Hopefully we can get it figured out.