Mounting a motor on a boat

[Old Crow]

I bought a used 2004 Lund aluminum fish boat with a 2004 Yamaha F115 on the back.
How do you determine the height of the motor when mounting to the boat?
The motor looks like it sits too high, the anti cavitation plate is above the keel of the boat.
The motor will start to cavitate if I have the motor trimmed up and start a not so sharp high speed turn

 

[86 century]

Re: Mounting a motor on a boat

The method most use is to start with the cav plate even with the keel. Test and tweak from there.

 

[Old Crow]

Re: Mounting a motor on a boat

If I trim the motor so the cavatation plate is parallel to the keel, the plate sits almost 3/4 of an inch above the keel.
You can see that the motor was mounted lower at one point in time.

What can I expect if I lower the motor?

 

[AGENT 37]

Re: Mounting a motor on a boat

More spray behind the boat if lowering it places the anti-ventilation plate below the keel, possibly a little less speed at WOT, better prop bite and less ventilation during your turn, and likely improved hole shot. General rule is that for every 12" the prop is behind the transom it can be raised 1" above the keel...... this applies more to off shore bracket applications though.