350 Mariner hull speed

[Punch'Eau]

Hi all, I own a 2000 350 Mariner since a couple of months and I still consider myself as a newbie to Carvers.
What is the hull speed and most fuel efficent speed for my boat?

[buster53]

Can't give you an exact number since I don't know your actual waterline length, but hull speed will be in the 7-7.5 knot range. Keep it at that speed or less. If you really want economy, slow it down to the 5-6 knot range.
What ever you do, DO NOT run it between hull speed and full plane. About the worst economy you can get would be in the 10-15 knot range, that is, short of balls to the wall, WOT.

[bud37]

We had a 2001 version with the stroker smallblocks......about 1600 rpm, 5 to 7 knts max. Like buster says either there or on full plane ( step). Just watch the size of the stern wave, it will be quite small if still within hull speed and not all turbulent. Just play with that visual as you push the rpms up and down.

They are surprisingly good on fuel even pushing a bit of a bow wave and digging in if ya want to get there a bit quicker.

[Punch'Eau]

QR_BBPOST Can't give you an exact number since I don't know your actual waterline length, but hull speed will be in the 7-7.5 knot range. Keep it at that speed or less. If you really want economy, slow it down to the 5-6 knot range.
What ever you do, DO NOT run it between hull speed and full plane. About the worst economy you can get would be in the 10-15 knot range, that is, short of balls to the wall, WOT.

Thank you

[Punch'Eau]

QR_BBPOST We had a 2001 version with the stroker smallblocks......about 1600 rpm, 5 to 7 knts max. Like buster says either there or on full plane ( step). Just watch the size of the stern wave, it will be quite small if still within hull speed and not all turbulent. Just play with that visual as you push the rpms up and down.

They are surprisingly good on fuel even pushing a bit of a bow wave and digging in if ya want to get there a bit quicker.

Thank you

[Alanna Mo Cree]

This is the fuel curve we put together for my 2003 360 Sport Sedan. You can see how quickly economy drops off as she approaches hull speed, which we calculated as closer to 6 knots than 7 knots based on the curve. There are essentially two sweet spots, 1000 RPM and 3800 RPM, with 1000 RPM being a LOT sweeter if time is not an issue.

chart.png

[Punch'Eau]

QR_BBPOST This is the fuel curve we put together for my 2003 360 Sport Sedan. You can see how quickly economy drops off as she approaches hull speed, which we calculated as closer to 6 knots than 7 knots based on the curve. There are essentially two sweet spots, 1000 RPM and 3800 RPM, with 1000 RPM being a LOT sweeter if time is not an issue.

chart.png

Very interesting. Thank you.

[Punch'Eau]

QR_BBPOST This is the fuel curve we put together for my 2003 360 Sport Sedan. You can see how quickly economy drops off as she approaches hull speed, which we calculated as closer to 6 knots than 7 knots based on the curve. There are essentially two sweet spots, 1000 RPM and 3800 RPM, with 1000 RPM being a LOT sweeter if time is not an issue.

chart.png

Just to be sure what are the numbers on the left??

[Alanna Mo Cree]

That is the range in nautical miles on the left (curve shown with 20% reserve). Speed is on the right. RPM at the bottom.

Don't take those numbers as absolutes though. Each boat, and I mean every boat, not just every model, is different. Every running condition is different too. The curve is more an indication of what to expect at various RPMs, but the specific range, speeds, and economy will be different on any given day even on the same boat. Generally speaking, the shape of the curve will be similar for every planing boat.

For example, we just did about a 300 mile round trip from Sanford, Florida to St. Augustine, Florida via the St. Johns River. Since we were going with the river current on the way there we burned only about 75% of the amount of gas as we did on the way back. On the way there we were also trying to go quickly due to various issues that needed to be addressed, so I was not trying to run economically at all. On the way back we were mostly taking our time.

[buster53]

QR_BBPOST This is the fuel curve we put together for my 2003 360 Sport Sedan. You can see how quickly economy drops off as she approaches hull speed, which we calculated as closer to 6 knots than 7 knots based on the curve. There are essentially two sweet spots, 1000 RPM and 3800 RPM, with 1000 RPM being a LOT sweeter if time is not an issue.

chart.png

FYI, Hull speed is a specific number based on a calculated math equation. In this case, hull speed is calculated by the square root of the boats waterline length X 1.34. To make this easy, let’s say you have a 38-40’ boat with a waterline of 36’. Square root of 36 is 6. Now multiply 6 times 1.34. Your hull speed is exactly 8.04 knots. The bigger the boat, the faster the hull speed. A yacht with a 100’ waterline would have a hull speed of 13.4 knots.
An aircraft carrier would be in the low 40 knot range.

Hull speed is defined by a calculated number based on size. It is not defined by the most efficient speed.