vintage chromoly

iTrader: (3)

hello all. i've been doing some research on the desired x dimension on an old 1977 pantera. the consensus seems to be 17 inches.

my question is this....do i measure from the center of the flat spot at the bottom of the transom where the v flattens out or do i hold a straightedge on the keel further up where it's a true "v" and carry that plane back to the transom and measure up form there?

i'm changing over from a volvo 280. i'm going to be running a bbc with a bravo 1. most likely a 4 blade prop.

thanks, rob.

onesickpantera

iTrader: (1)

I measure from the small pad since that is what is riding in the water. If it were me I would do 18".

IRONMAN

+1 on measure from the pad. 18" will require you to use an external water pickup or a dual water or low water pickup lower.
What displacement and HP are you planning on running?

vintage chromoly

iTrader: (3)

i'm looking to run in the mid 70's. i'm thinking 500" and 500 hp/550ft.lbs. of torque. (i still have a lot of research and talking with my engine guy to do)

i want the boat to be stable at speed so i'm afraid to raise he drive too much. is it better to go higher than 17" on the x dimension?

thanks, rob.

onesickpantera

iTrader: (1)

If I remember right I am 17.25" and Jo said the US Army boat was at 18", which is why I recommended 18".

I would love to try a 1" shorty on my boat. My theory is the higher propshaft would require less trim to get the prop at the sweet spot, which would equal less positive trim and in turn less bow lift and a possibly a more stable ride. But, that is just a theory.

BTW, 500hp and 550lbs of tq will get you mid 70s.

Griff

A higher X will reduce the ability to carry the bow as well. If it doesn't carry the bow, the boat will run wetter, flatter and slower.
That being said, I don't think going 18" would create any issues that could not easily be changed with the right prop or 1/2-1" spacer.

onesickpantera

iTrader: (1)

I agree on the bow lift which is why the 24 would respond well to a higher X. IMO the 24 has too much bow lift.