How high to hang F115

[SthurmanFW]

Hope all the Florida folks on this forum are safe, especially Keys folks. Not expecting much response to this question in the short term as many don't have power or cell service but here goes.

Does anyone have any advice about how high to hang a 2004 Yamaha F115 on a 2004 HPX-18, I've read on here that most people don't think jack plates work well on these hulls(more weight, farther back, no tunnel etc). I have noticed mine really struggling to run as shallow as I think it should. It's currently on the lowest hole so I could potentially raise it up a few inches if I went to the last hole down. 

Anyone have any experience either positive or negative with moving the motor up some, I've heard that it might even correct some of the porpoising which seems counterintuitive but I'm willing to try it. Plus hoping it might run just a shade shallower and we all know it's a matter of inches sometimes whether you are stuck or not.

Thanks everyone

[Jscann]

I did some trial and error with mine to squeeze all the speed I could . And found my motor like it two holes up. So the motors mid section lip is like 2" over top transom. Or pop a level on the bottom of boat and set it to the cavitation plate

[fishmanjj]

If you mount it too high, it will " blow out" when you go into curves....you will instantly hear it cavitating and see an increase in rpm and no increase in speed. You will have no doubt that the motor is mounted too high. Personally; with my F150 on my 2200, ( no jackplate ) I started very high and just kept lowering it until it performed well and would go into curves at almost full throttle with no slipping. 

Of course, the prop you choose will also play into the equation of performance. 

 

 

[SthurmanFW]

Thanks guys, is there a direction I should go in choosing the right prop when moving the motor up, I'm totally naïve when it comes to props. So ignorant in fact I don't even know what's on the engine right now except that its a four blade and seems to have a decent hole shot but not in shallow water.

 

[BLawson]

20 hours ago, Jscann said:

I did some trial and error with mine to squeeze all the speed I could . And found my motor like it two holes up. So the motors mid section lip is like 2" over top transom. Or pop a level on the bottom of boat and set it to the cavitation plate

Do you have any pictures of the prop level and the bottom of the Boat?

[SthurmanFW]

Going to check all that tonight

Have done some exhaustive(zzzz, nap inducing) research on youtube today while I should have been working

Ill try to get some pics if I can tonight also try to figure out what pitch prop I have and get back with you guys

thanks for helping me with this, I know its truly impossible without water trials with each adjustment but just needed a starting point

[SthurmanFW]

Dont know if this helps or not, from the actual bottom of the transom it looks way too low, there is that cut out section in front of the true keel that the drain holes are in, not sure which truly represents the "bottom" as far as measuring the cavitation plate height, thanks again!