Hull Speed

[RGrew176]

I have a 1981 3007 Aft Cabin powered by twin 270 Crusaders (5.7's) I have a trip coming up next week. It is just under a 40 mile run. I am contemplating trying to make the crossing at hull speed. On this boat I am not sure what speed that would be. What I am thinking of is powering up to 2000 RPM which should give me a rough speed of 9 MPH or so. Is this setting to high. Should I use a lower setting say 1500 or 1600.

If any other 1981 or 1982 3007 owners have done this give me your input as to what settings worked out best for you.

[g36]

here is a link to see your hull speed, you'll see your 9mph is too fast.

https://www.easycalculation.com/physics ... ulator.php

[RGrew176]

Using the link above I put in 30' for my boats waterline length. Boat is 29' 11" according to my owners manual. The speed that came up when I put in the information was 7.3395 knots. That calculates out to 8.446 MPH. So, 9 is to fast but 8.4 MPH should work out OK. If conditions allow on Monday when I head out I will give the 8.4 MPH a try.

[bud37]

The waterline length of any boat is considerably less than the LOA or the centreline length....my guess for a 30' boat would be closer to 26'.It is measured from the bow waterline to the transom waterline.Some are longer and some shorter depending on the hull design........our old 32' hull speed was about 7 knots max then you were pushing water.

[g36]

Yes x2 length at waterline not loa

[RGrew176]

Qr Bbpost Yes x2 length at waterline not loa

Got it.

[RGrew176]

Qr Bbpost The waterline length of any boat is considerably less than the LOA or the centreline length....my guess for a 30' boat would be closer to 26'.It is measured from the bow waterline to the transom waterline.Some are longer and some shorter depending on the hull design........our old 32' hull speed was about 7 knots max then you were pushing water.

Using this formula, and I will check it when I go to the boat again I should be somewhere between 26' and 27'. Appreciate all the information provided.

[RGrew176]

Using 26' as a start point I get a speed of 6.8327 knots or 7.8629 MPH.

Using 27' as a start point I get a speed of 6.9628 knots or 8.0126 MPH.

My first destination on Monday is about 35 miles away so I am looking at a 4+ hour cruise if I decide to try the hull speed thing.

[g36]

also check this website. its pretty accurate from what i have seen. i have referred it to others that have reported it pretty accurate also. just select your engine manufacturer and then select your hp. it shows fuel burn at various rpms. might help you get a estimate on your trip

http://www.boat-fuel-economy.com/fuel-c ... calculator

[RGrew176]

I just want to experiment with various throttle settings so I can get a feel for fuel consumption. My last boat I had down pat. This boat I am still learning.