hum noise at 20mph to 21 Mph

[ddickens]

I test drove a Tige today and found that the boat had a hum at 20 mph to 21 mph. It did not matter how you approached that speed. I am new to boating and wonder if this is common at certain rpm's and is caused by harmonic vibration or if it is an issue of the boat. The boat is great and I want to move forward but not if there is an issue. Any feed back would be helpful.

Thanks,

David

[Flying Tiger]

It either the sound system is outta range of the radio station,,
or the bildge pump is on manual.

[Tige M.D.]

alot of the older tige's had a hum to them. i remember sitting on the beach and with my eyes closed and you could tell when a tige was coming. alot of it had to do with the harmonics of the underwater gear. mainley the prop. the old 3 blade s/s prop was pretty load.

is the noise more like a high pitch whin or a low pitch growl?
does it change in turns?
will it make the noise in neutral at the same rpm?
is the motor black or grey?
efi or carb?

[ddickens]

It is more like a high pitched hum. The engine is black and does have a carb. The noise does go away if I turn. I will try to see if it makes the same noise in neutral. It is almost like it is caused by water going over the underside of the hull?

[GIZMO]

It may be caused by the tracking fins, if they are perfectly lined up the center fin can vibrate. Bend it out a little with a rubber mallet, just slightly dont get crazy on it. If the noise changes go a little more until its gone.

GIZMO