My last post refers to this. Sorry for posting again but I really need some info on this.<br /><br />My boat has just been re-engined with a new, out of the crate Yamaha F-40 4 -stroke. When run in gear on the muffs & hose there is a rattle from the gear box. The sound comes and goes. The Yamaha dealer initially thought it was a faulty gear box. He was going to order a new lower unit until he started a Yam F100 4-stroke with 10 hrs on it. It made the same noise on the muffs. A 10 hr F115 was significantly quieter but the noise was still there. The noise is there at idle revs and higher revs, up to 2.5 k was tried. It doesn't get any louder as the revs increase and follows the same pattern of stoping and starting. <br /><br />Is this to be expected, when in gear, out of the water, as there is no load on the prop, or should the gears be silent as they are in bearing races and bathed in oil?<br /><br />It would be great if an experienced Yamaha tech could answer this. <br /><br />Thanks to those who have already replied.
