I have twin 200 HPDIs on my 252. In the last 5 months, I've only run the boat at low rpms on a hose (live in FL). The last time I had the boat out, the engines did fine. This past weekend, engines ran fine at idle and low rpms. When I tried to get on plane, one engine stopped responding to throttle advance above 2500 rpm, i.e., going to WOT did not result in an increase above about 2500 rpm. The engine did not choke, die, sputter, or may any unusual noise, just no high rpms. I took the engine out of gear and the rpms increased with throttle increase just fine - above 4600 rpm. I did not want to chance it going higher since I didn't know what the problem was. Did this several times. Got the boat on plane - mostly with the good engine- and ran for a few minutes. Moved the throttle back and forth, but the problem engine never got above 2500 rpm. No alarms. I use non-alcohol gas and ring-free. The fuel filters are clean, new fuel hoses and tanks. The engines were bought used. I did not change out the low or high speed pumps, internal screens, & so forth. I will probably have a mechanic look at it next week. But would like to hear if anyone else has had similar issues. Thanks.