prop height

[dshen56]

I just bought a jon boat (14 foot) it came with a long shaft motor 9.9 mercury force.I have to modify the transom to get the proper height for the motor to sit on. My question is ,how far should the prop be under the bottom of the boat to get the best perfomance? That will let me know how high to modify the transom.
Thanks rick

 

[Silvertip]

Re: prop height

Start with the antiventilation plate (the flat plate just above the prop) even with the bottom of the boat.

 

[Silvertip]

Re: prop height

Another way to do this: Standard motors measure 15 inches from the AV plate to the transom bracket. Long shaft measures 20 inches. With that in mind a 5 inch riser on the transom should put you in the ballpark.