I have owned this Outboard for about six years. The engine is a 2000 90ELPT 4S. I purchased it used and the first time I took the boat out it bogged at throttle. Calling the boat shop they said it was probably the old gas. I replaced the gas and it seemed to run OK for 3-4 trips then I had the same issue, it would start up and idle fine, get up on plane, run a while then start to cut in and out not running at 5500 RPM closer to 4500. I changed the fuel filters and the gas again but still had the same problems. A year later I finally took it in to a repair shop they said compression was good the fuel pressure was good and diagnosed the problem as a bad thermostat never letting the engine get up to optimum temperature. The boat ran good for maybe 1-2 trips then went back to it same old problem of loosing power at full throttle cutting in and out and never reaching full RPM. I changed all the plugs, new fuel filer on engine, changed the fuel hose and fuel siphon pump. Took it out last week same problem. Any thoughts?