Prop to pad measurement with no pad

[jimlaw83]

Looking at installing a 6” HD jp this winter on the old Nitro 185 sport. Problem is, while the boat has a substantially notched transom with inset flat pad, the hull rear matches current z19 sports and has no “pad” to speak of, just a slightly reduced dead rise V between the first level of strakes. There is at least 6” of notching setback from hull rear bottom to transom, and current non-jp motor is set with prop running only about 1” below bottommost extreme of the hull V, which works out to about 5” below the transom notch level.

Question is should I honestly set prop below the hull V, or work off the transom notch/pad? From what I understand the hydrodynamics allow about 4.5” of vertical adjustment (my access to engine lift and shop equipment is limited for later changes). Any help or info would be greatly appreciated!

As a side note with the old merc 125 elpto and laser II 13x19 prop and properly zero’d trim gauge, I can trim out just under halfway up gauge (ie needle is dead just short of dead vertical) before prop venting occurs.

[pmgoffjr]

The very lowest point on the hull. That's your "pad" regardless if it's flat, v or concave. Once you install your plate, you shouldn't need anything but a wrench to adjust it.

Trim gauges suck, drive by what the boat tells you.

[Snoopy Rod]

The very lowest point on the hull. That's your "pad" regardless if it's flat, v or concave. Once you install your plate, you shouldn't need anything but a wrench to adjust it.

Trim gauges suck, drive by what the boat tells you.

+1 ^^^^^^^

[JR19]

This picture explains how to measure motor height/prop to pad height. The pad (regardless of shape) is the lowest portion near the rear...

[jimlaw83]

Appreciated much! HD 6” magnum will be put on order next Monday. Guess I will need to make the decision after install whether to send the 13x19 laser II sitting in box to MC for repitch and cup or just see if I can exchange for a 20-21”. Luckily I live near Delta prop so hopefully can test a few on Ohio River.