What cruising speed?

[John N]

Hi,

We have a twin gas engine Campion 30ft cruiser with plans to boat from Reed Point to Desolation Sound. I'm wondering what is the optimal cruising speed for this type of vessel?

1. Should we crawl at below 10 knots, without getting on plane?
2. Should we get on plane at 28 knots and continue cruising at this speed?

I'm just wondering what is optimal. This boat is still new for us. Thanks!

 

[kaelc]

What year and model? There is likely a hull speed of 6-8kn which is optimal for mpg and then a cruise speed in the 18-22kn which is optimal for comfort but also getting where you want to go without having to stop at every fuel dock.

 

[Srthomas75]

I would guess that the slower the better for mpg.
There was a website that compared motors’ gph consumption at different rpms for rough ideas.

 

[Srthomas75]

Fuel consumption calculator - MerCruiser - Volvo Penta - Crusader - Mercury - Evinrude - Honda Marine - Yamaha Marine - Suzuki Marine - Tohatsu - Johnson - Outboards | GPH MPG LPH KPL

Fuel consumption calculator - MerCruiser - Cummins MerCruiser - Crusader - Volvo Penta Diesel - Mercury - Evinrude - Honda Marine - Yamaha Marine - Suzuki Marine - Tohatsu - Johnson - Outboards | GPH MPG LPH KPL

www.boat-fuel-economy.com

 

[Aces]

Hi,

We have a twin gas engine Campion 30ft cruiser with plans to boat from Reed Point to Desolation Sound. I'm wondering what is the optimal cruising speed for this type of vessel?

1. Should we crawl at below 10 knots, without getting on plane?
2. Should we get on plane at 28 knots and continue cruising at this speed?

I'm just wondering what is optimal. This boat is still new for us. Thanks!

I would try around 12-15 knots. I always listen to where the engines sound happy. Not working hard. That’s when mine has its best miles per gallon.

Suggestions:

Start off with full fuel tank
2- You didn’t mention if it has a fuel management system. If it does you’ll figure your most efficient speed quickly

 

[John N]

2008 Campion 925LX

Twin mercruiser engines

Boat gets on plane at around 26-28 knots but I feel like for a longer trip it burns thru fuel quickly

But also not sure if going 16-17 knots (not on plane) is any better? Much more comfortable ride though

Thoughts ?

 

[Samnjoe]

I would think you would need to be on step.
Hopefully around 25 mph?

 

[Rain City]

The hull speed of a displacement or semi-displacement vessel can be estimated using the formula:

Hull Speed (knots) = 1.34 × √LWL,

where LWL is the length of the waterline in feet.

For the 2008 Campion Allante 925 LX, the length at the waterline (LWL) is approximately 8.53 meters, which converts to about 28 feet.

Applying the formula:

Hull Speed = 1.34 × √28 ≈ 1.34 × 5.29 ≈ 7.1 knots

Therefore, the theoretical hull speed is approximately 7.1 knots.

It's important to note that the Campion 925 LX is designed as a planing hull, which allows it to exceed this theoretical hull speed. In fact, it can cruise at around 19 knots and reach a maximum speed of approximately 28 knots, depending on engine configuration and load.

Anything between planing and hull speed is not where you want to be. Figure out how slow you can go before you "fall off". It takes a lot of playing with your trim and (most often) moving weight forward. You do have to be mindful of how overloaded you are because that will affect things a lot. Boats shouldn't be treated the same as loading up your truck for camping. Good luck.

 

[Aquaholic]

Here is another way to look at it. If they are V8 motors, any magazine boat test I’ve ever seen shows the optimum miles per gallon cruising speed is found at 3500 rpm. Are you still on plane at 3500 rpm?

 

[Samnjoe]

Get a fuel flow meter and tie it in to you chart plotter.
Run it well on step. That boat will definitely burn some fuel. Running to Desolation at hull speed would be painful

 

[kaelc]

If it’s heavily loaded trim tabs and different props might help getting on plane and staying on plane at low to mid 20’s. I don’t know if there is a campion forum or Facebook page? My brother runs a similar size bay liner and both helped, he usually runs in the low 20’s.

 

[John N]

I think you guys are right. We can get on plane at around 25 knots while keeping RPMS fairly low, boat doesn't seem too strained.

 

[Max123]

That's interesting that you need to be going 25knot (28.75mph) to get on plane. Is this typical for large boats? 28mph is a normal fast cruise speed for me (obviously way smaller boat), and I can take it down to low 20s if I want to really crawl on plane.

 

[Rain City]

That's interesting that you need to be going 25knot (28.75mph) to get on plane. Is this typical for large boats? 28mph is a normal fast cruise speed for me (obviously way smaller boat), and I can take it down to low 20s if I want to really crawl on plane.

My old 24 Bayliner was like that. Underpowered and butt heavy.

 

[zurk]

usually you want to cruise just on plane. thats when the boat is most efficient. too fast and youre burning fuel to move fast, too slow and youre pushing water away which is max drag on a planing hull. so get on plane, put it back one notch so it hangs just about planing speed and leave it.

i plane at 3600rpm while my WOT is 5600rpm so for me thats most efficient.

 

[easydoesit]

You can calculate optimum cruising speed for your planing hull if you have the following data for your boat: fuel consumption rate, rpm’s, speed over ground. Takes 2 people, one to drive, one to collect data. For some models of boat you can find data on line. My optimum cruising speed data matched with theoretical fwiw. Depends on conditions though, eg wave height, probability of floating objects.

For a large thirsty engine like mine exceeding optimum planing speed really increases my fuel costs.