strange noise?

I have a 1993 40hp 2stroke that has developed a noise in the gearbox. When we left the boat ramp it was fine , went to full throtle for a while ,then slowed to 6 knots and could hear a rattle type sound that appears to be coming from the gearbox. Motor still goes well and the sound is still there in neutral. Any ideas would be helpful...

[boats.net]

Check the gearcase oil for metal particles.

I have checked the oil and there was no metal particles anywhere. Also took the bottom leg off and checked the impellor and end of drive shaft and it all looks good . However when the motor is in reverse and i turn the propellor manually in either direction the engine turns over but when it is in forward and i turn the propellor manually the engine turns over in one direction but in the other direction the shift rod jumps up and down and the engine does not turn over is this normal ?

[boats.net]

Yes that is normal, did the oil smell burnt?

The oil did not smell burnt at all. we are at a loss we may have to take it in to a mechanic to see what they say. Thankyou for your replys mate