I own a chaparral 26ft cruiser fitted with a Mercruiser 5.7L EFI engine.<br /><br />I am experiensing a very unclear fault as follows. I take the boat out and start giving it throttle to get the revs up. The boat planes at 2800rpm and everything seems fine. I continue giving throttle until I reach a cruising speed at 3300rpm. After a few seconds the rev counter starts going down slowly for no apparent reason and the speed reduces. I give more throttle, but mothing happens and the revs keep going down. The only way I can get back to cruising speed is by pulling back on the throttle for a few seconds and applying the throttle again. This gets the revs up again but only for a very short while because this thing repeats itself indefinitely.<br /><br />I have replaced the high pressure fuel pump for nothing, I have checked the EFI system with the digital scan tool but everything seems OK. I have checked fuel lines and fuel vent but everything seems normal.<br /><br />Can anyone help me??