boatmike
Well-known member
This should be fairly simple but isn't easy to find...
I have a 4 cylinder Vetus engine in a central location above the WL on a Snowgoose Cat driving a Sillette outdrive leg via a flexible coupling (no intermediate shaft)
I have a cyclic noise that sounds like resonance but is not in time with engine revs or prop revs. The best I can describe it is like "hunting" which you sometimes get with twin engines at about 1-2 second intervals. Rumph-rumph-rumph--- If you see what I mean!
I thought it might be an out of balance prop, but have just fitted a new one with slightly courser pitch.... still the same! I cant see anything out of line, the engine does not appear to move on its mounts, the leg itself is on a good mounting and not loose... Where the hell is it coming from? It doesn't seem to do any harm but is driving me bananas! I once had a boat where the cooker would resonate in a similar fashion at one RPM but changing the speed would stop it. This comes in at about 2500 RPM and just gets louder up to max throttle. Anyone got any ideas? /forums/images/graemlins/confused.gif /forums/images/graemlins/confused.gif /forums/images/graemlins/confused.gif /forums/images/graemlins/confused.gif
I have a 4 cylinder Vetus engine in a central location above the WL on a Snowgoose Cat driving a Sillette outdrive leg via a flexible coupling (no intermediate shaft)
I have a cyclic noise that sounds like resonance but is not in time with engine revs or prop revs. The best I can describe it is like "hunting" which you sometimes get with twin engines at about 1-2 second intervals. Rumph-rumph-rumph--- If you see what I mean!
I thought it might be an out of balance prop, but have just fitted a new one with slightly courser pitch.... still the same! I cant see anything out of line, the engine does not appear to move on its mounts, the leg itself is on a good mounting and not loose... Where the hell is it coming from? It doesn't seem to do any harm but is driving me bananas! I once had a boat where the cooker would resonate in a similar fashion at one RPM but changing the speed would stop it. This comes in at about 2500 RPM and just gets louder up to max throttle. Anyone got any ideas? /forums/images/graemlins/confused.gif /forums/images/graemlins/confused.gif /forums/images/graemlins/confused.gif /forums/images/graemlins/confused.gif