Engine noise

[Glenn Abuelhaj]

Yamaha Pro V 150 running a 23-M2 Yamaha Pro prop. Everything is stock. I can get to full speed but when I slow down to ~3100RPM's, and cruise at ~3500 RPM's, I hear what seems like a baseball card running through spokes from the engine area or something slapping in the wind. But, when I punch it, the noise goes away. Also goes away below the 2700 or 2600 RPM's too. I verified that the fuel pumps are tightened (thought maybe sound was coming through vascuum holes for the diaphrams). Also check plugs. They are normal. Motor starts and runs fine, hasn't lost any power or punch, and idles really well. I'm thinking check valves in the priper bulb? Or the prop spinning too fast for the speed, or a Lower Unit problem? I have a 25M prop that I'm going to try and will check LU oil for metal parts. Also, could the reeds makes this type of noise?

Any ideas or experiences?

Thanks!

Glenn

[jb123]

on your pro i THINK you have spring loaded butterfiles which cause that sound and is normal. careful to NEVER choke while rpms are above, say 1500 as your intake will suck/shear them right in.

[Glenn Abuelhaj]

hmmmm. Never thought of that one. Is there anyway to make corrections ie. replacing only the springs? I'll take a look at them this week end and see what's there.

Thanks for the tip on the choking. I don't think I ever done that!

Thanks for your time!

Glenn

[jb123]

they are designed to work like that.
after shearing mine off , i bought a set of used carbs and used the full/solid butterflies.