I have a 454 mercruiser in a 24' Bayliner with a 280 VP outdrive. In nuetral it runs just fine. I can bring up the rmps to redline if I wanted but I wouldn't. However, under load I can only throttle up to 3600 rpms which is just above half throttle. If I try to push it more it wants to cut out, stall and not take any more gas so I have to back off of the throttle. Could someone please shed some light on this or give me a few things to look for?