Strange noise

[Captain Dave]

I have a brand new 225 Yahmaha with 50 hrs on it.It runs fine but has always made a strange rumbling sound at its lowest rpms while making way.As soon as you give her a little gas the sound is gone at all other speeds but when you back the throttle all the way back down to its lowest speed ,the sound returns(sound is intermittent-quiet for several seconds then rumbling then quiets down again several seconds later.What could this be?

[boats.net]

You didn't say what model you have but could be prop chatter or drive shaft bushing noise(on some models).

[Captain Dave]

Model

Sorry,Its an F225TUR 30".

[boats.net]

May need to remove gearcase and grease upper drive shaft(splines and oil pump seal area) and housing bushing.

[Captain Dave]

O.K.

Thanks.I'll try this and see what happens.Dave.