Mounting height for new motor?

I bought a new 50hp yamaha 2stk tiller handle for my 2001 Nova Ultra Jon Pro Weld MVJ. The problem is at high speed the bow wants to start going up and down. My ques. is do I have it mounted to low, the fin just above the prop is maybe 1/4 below bottom of the boat, ohh yea I am a pretty big guy 6'5" 330lbs. Any sugg. or links to sites that offer tips or tricks will be greatly appr. Thanks, Grant :?:

The problem is more than likely not the height you have it mounted, but instead the trim. You probably need to trim (tilt) it down a hole or two, if you have manual trim, or tilt down to almost the bottom if you have power trim.

I should have mentioned it has power trim/tilt. It porposies at high speed when the motor is trimed all the way down as it is when I come out of the hole, it improves as I trim it out but is not completely eliminated. It gets to a point were it does not do it at a certain trim level but it is at about 2/3 throttle, and everbody wants to be able to run at WOT. Would a Hydrofoil help my problem, I havent read very many good things about them here but I do have an SE 300 on another motorthat I could put on to my new motor. Also does the prop have anything to do with it, (pitch/diameter). Thanks guys

I hydrofoil will cure it but it may lose top end and will catch vegetation.

Props will affect it as well but it is more of a cup issue than diameter/pitch. My boat wants to porpoise now at lower speeds since I changed props. It never did that with the original.

Try moving some weight forward. You can also put some hook into your hull and solve the problem without the hydrofoil.

Quackrstackr said:

Try moving some weight forward.

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I would try this first also!...It's the cheapest test.

My boat does the same thing, with one person in the back i cant break 25 without it getting out of control. i have the problem because i have 3 times the max engine on the boat, way to much weight in the back. when i have someone sit up front it isn't a problem. so i would say try to move some weight up front, if your battery isn't already up front try moving it. i made some trim tabs on my boat, but i haven't tried em yet, i will let you know how that works out after tomorrow night.