Vintage Mercury set up

[BobbyZ28]

I am restoring a 15' Allison Craft built in 1965. New transom is installed. I have a 1976 model 1500xs to power it. The lower unit is the typical size unit not a speedmaster. My question is how high should the engine be mounted on the transom. This is a FLAT BOTTOM Allison boat. Not a V bottom. I have been told the bottom of the boat should be in line with the cavitation plate and also been told that the bottom of the boat should be in line with the prop shaft. I am open for comments and suggestions. Thanks!!
Bobby

[OnPad]

You want your cavitation plate above the bottom of the boat. You don't want in in the water while on plane.
If looking for top speed. Raise it as much as possible, till you start losing water pressure. Then drop it down a bit. You won't be able to get prop shaft even with the bottom of boat with a stock lower, unless you use a low water pickup. Prop shaft 3" to 4" down with stock lower.
The higher you mount it, the more prop you'll have to use.
Steering also becomes problematic.

[OnPad]

Be sure to wear a life jacket and kill switch. That is going to be a wild ride.

[BobbyZ28]

It has a standard size lower unit with the low water pickup.

[SCT]

What’s the estimate blow out speed of a standard early 70s I6 lower unit?

And do these older Mercury water pick ups work good on I6 lowers?

https://www.amazon.com/Mercury-Mercr.../dp/B00N9HK0HO

[OnPad]

Idk I never tried going that fast with one. Sounds about right. Unless you put t. tamer on or increase skeg size.
I think I read on here where someone was running one on a drag boat with a v6.