rattling noise

[Joker2]

Spoke to my mechanic, told him I have a rattling noise only between 3,000 - 4,000 RPM's he told me to add oil to my gas 50:1 just to see if the rattling noise goes away ( in case VRO isn't working ), then check to see if there is water in the lower unit oil. If not then he will look at it. ( I have to borrow a trailer just to bring it in. It is on a mooring at a remote location -- Pain in the but ) Motor ran fine (up to 5,500 RPM )with extra oil, noise still there, have to pull it to check lower unit oil. Oil was changed last fall for winter, as I do every season, old oil was fine when I changed it. I also found a missing cowling bolt, I installed a new one after this extra oil trial run. Trying to do one thing at a time. I might run it one more time with the new bolt just to see, but I don't think that is the problem. Any thoughts

[RidgeRunner]

Any way it could be the latches on the cowl? My Johnny will cause the latches to buzz at a certain rpm. The solid mounts on the Merc buzz the entire boat, LOL. Someone on the board recently had a tilt pin that was rattling. If you could have someone drive the boat while you are back at the engine checking on things, it might help. Best of luck.