79Invader
Seaman Apprentice
- Joined
- Apr 23, 2019
- Messages
- 45
Hello. My 1990 mercruiser 5.0 throttles right up and gets on a plane just fine. Runs about 40 mph at 4600 RPM. After about 60 seconds of running wide open it starts to lose RPM’s. Once it’s down to about 4000 RPM there’s an audible “clatter/rattle” coming from the motor. Throttle down and idle for about a minute then gets right back back on a plane 40 MPH 4600 RPM then repeats. Seems to have the same issue if you’re not running wide open say 3800 RPM just takes a little longer to happen. Will idle all day no problems. What could be the issue? I’m thinking fuel delivery but does that explain the clattering? Any insight is appreciated