I have recently upgaded a 16ft Flightcraft Bowrider(australian shallow vee fibreglass) Hull froma 100Hp Merc to a 135Hp. <br /><br />I had problems after switching motors when the 135 wouldnt idle & had bad problems taking off, especially when towing skiers. It finally turned out, after much frustration & expense that the increase in motor weight was causing the stern to sit lower and meant that the exhaust reliefs at the top of the column were sitting under water at idle & take off causing back pressure. The problem was much better with someone sitting up the front.<br /><br />First step was to fit another relief higher up on the column exiting through the fixed panel on the back of the cowl bracket via a new model's flexible rubber tube. This gave a bit more relief higher up and out of the water. Still not happy we added 6okg of sandbags in the Anchor Well which has heped even more.<br /><br />We now have a boat that idles, pops up onto the plane effortlessly and punches through chop with more confidence.<br /><br />This could be a problem many others are experiencing with no diagnosis. <br />I would also like to hear frommanyone with more advise or suggestions about this problem.
