Lowe Stinger 18 HP low rpms with little trim.

[Tomtom3975]

I've recently bought a 2014 Lowe stinger 18 HP 115 Mercury pro xs has 15 hrs. Motor was mounted in the very top hole from factory has 12.5 x 19p aluminum prop. Top speed was 43 mph at 5200 rpms factory tach and gps loaded with little trim before it starts pporpoising. Done some research and found alot of owners and Lowe themselves was using a laser ii 22p prop on the 115. So purchased the prop brand new. Installed and got 40 mph at 4800 rpms. Decided motor needed to come up moved to the middle hole so up 2 holes tried and got 43 mph at 5200 rpms. Put the original prop on and got 44 mph at 5500 rpms. My trim gauge shows 3/4 mark as Soon as the tail of the motor touches the top of the water planned out on the very bottom mark can't trim no farther then the porpoising starts. Read on a forum of Lowe adding wedges, trim tab, or some type of bead. So question is what do I need to do to get this motor to redline to get the speed everyone else is getting. Thanks.

[Rip Bass]

All of those wedges,tabs and beads are to control porpoising at slow plane speed,not what you have. Your high end porpoising is caused by the prop not having enough bite to keep the bow up. It tries to lift,loses bite,bow falls and starts all over again. You can go to a lower pitch prop and have some cup added( because you will lose rpm if you add cup to what you have) or install a 6” jack plate. Setting the engine farther back will add leverage to allow the prop to keep the bow up and you can raise the engine if needed. I would go with a jack plate,personally. Check out Vance Manufacturing for one of their plates,fairly cheap and it’s a good plate.