How To Achieve Better Inboard Engine Boatspeed
August 5, 2009 by Chris Wethered
Filed under Boat Electronics And Nautical Navigation, Questions Visitors Are Asking And Answers
If your thinking about whether your inboard engine boatspeed is up to scratch, this article is written to get to the bottom of that question.
Before giving you the resource to go off and try, it's best to understand what the variables are behind finding the best from your motor.
The basics of velocity are governed by variables where one factor has an impact on another.
Ahead of you going out buying a brand new engine, why not get the most out of the one you've got at the moment? Here are some variable that need to be kept in mind:
Pitch
The theoretical distance the propeller travels in one complete revolution. This is subject to slippage, which is covered a bit later. Slippage reduces the distance traveled by the blades through the water, so lowering efficiency.
Diameter
Is the distance, doubled from the center of the propeller to the outer most point of a blade. As the number of blades varies, this method is best to calculate diameter.
Slip
We looked briefly at slippage early, here is some detail. This is the percentage lose in distance that the propeller looses as it turns through the water. Effectively slippage reduces the ability of the propeller to develop drive, forward or back. The percentage lose is in the area of between ten and thirty percent.
Inboard engine boatspeed run
Cavitation and Pitting
Cavitation is the formation of air bubbles on the blades. The bubbles are the product of interference in the aqua dynamics of the boat. Simply put, if barnacles are growing on the hull, in front of the propeller, their profile on the hull causes a disturbance in the water. Bubbles form and float back to the propeller blades. Firstly the bubbles act as a barrier to the blade getting traction in the water. This in effect is slippage.
Secondly, oxidation of the blades increases. This is the beginning of pitting. If the barnacles or the depth sounder is not removed or replaced elsewhere on the hull, the effect of the cavitation becomes profound. The oxygen rich bubbles attack the propeller blades. Causing pits to develop. If there is any previous damage on the blades then pitting will result quicker.
As you can imagine, cavitation and pitting can have a big impact on your propeller's abilty to drive your boat through the water. The degree of slip also increases, which lowers efficiency.
Blade thickness
The design of the propeller and construction material used, determine the thickness of the blades. The thinner the blades, the lower the drag.
Cupping
Is the angle at the propeller edge. Cupping is used as an adjustment to assist pitch. The angle at which the water leaves the surface of the blades is a factor in establishing distance travelled through one revolution.
Really the pitch is the most important aspect of getting the best boat speed out of your inboard engine. If the theoretical distance the blades travel through one revolution is maximized, then optimal speed is reached. If contributory factors are reducing the distance travelled through that revolution then the result is lower speed.
Keeping the hull and prop clean lessens cavitation risk
Time to get on the water!
- You will need a tachometer and speedometer
- The engine manual
- Calmish water
First off
From your engine manual, find out the range of RPM that the engine is designed to reach at full throttle
Find a piece of water, which is large and queit, so you can do test runs unhindered, in safety.
Establish a benchmark over a few runs. Note down RPM and boat speed on each run.
If your RPM exceeds the range indicated in your engine manual, then the pitch of your propeller needs to be greater - increase propeller size
If your RPM is lower than the range indicated, then the pitch of the propeller should be lowered - decrease propeller size
You should note that changing altering the size of your propeller by one inch up or down, changes the RPM by a factor of 250. So engine speed will increase by 250 RPM if you decrease the propeller size by one inch. Engine speed will decease by 250 RPM if your increase the sixe by one inch.
Once you have reached maximum RPM when you have completely opened the throttle, then you will be getting the best boat speed you can from your engine.
This method is a simplified one. If you are looking for a more complex formula that includes total boat weight etc, then click on Recreational Boat Building Industry for further information.
It's time to pour on the goodies with West Marine! That's right! When you spend over $100 you get 10% discount!
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Multifunction Navigation System
July 22, 2009 by Chris Wethered
Filed under Boat Electronics And Nautical Navigation
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Touch Screen Chartplotter
July 22, 2009 by Chris Wethered
Filed under Boat Electronics And Nautical Navigation
By packing together components, the savings are all yours. More components - more savings!
As ever you can punch in all your regular waypoints and plan your boating accordingly. If your planning a voyage, then this GPS will be a valuable asset. Or you would like to be able to keep up to date with new technology. The software is able to do that and a lot more.
Let's start with:
- Preloaded offshore chartplotter with marine cartography of coastal US, includes Alaska, Hawaii and Bahamas
- Sounder module - to find the fish!
- Weather module - to find out the weather before it finds you!
That's all brought to you on a:
- Huge 12.1' screen!
All of that comes as standard! Want to break out the big guns?
Excellent!
You can supplement the video quality resolution screen with vision cards that bring you:
- Enhanced mapping - added detail
- 3D views - see what's going on under your keel!
- Hi res satellite images - courtesy of the global network
- Aerial photos - helping you see beyond the horizon
Look! No Buttons!
Further add ons bring:
- Detailed sonar data - GSD 22 digital tracker
- Subscription weather service - GDL 30A receiver
Interface in/outputs as follows:
- 3 built in network ports - providing information relaying
- 4 NMEA inputs - offer inter brand compatibility
- 2 NMEA outputs - offer inter brand compatibility
- 2 video inputs for onboard cameras
- 1 VGA PC monitor for video output
- 12 channel WAAS receiver
- IPX 7 submersible
Guaranteed for two years
Buying the GPSMAP is an investment in your nautical navigation. It's possible to adapt your console by bringing in new components, even inter brand. Either way, you are extending the ability of your all in one console presentation.
As your confidence grows with the original set up, you can personalize your console bringing more functionality to your finger tips - remotely if you like!
Please watch the demonstration video:
Want more for your money? West Marine are giving away 10% on orders over £100!
Related Posts
To raymarine chartplotter Need marine chartplotters? Look through marine binoculars Listen to handheld vhf radio
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Tahiti Binoculars
July 10, 2009 by Chris Wethered
Filed under Boat Electronics And Nautical Navigation
Do Your Binoculars Mist Up When Your Using Them? Here Is The Solution
The practical use, design led features of Tahiti binoculars are winning awards! Feed back from leading edge sailing has been taken in to consideration. Solutions have been put forward and behind the scenes work has been recognized.
Dependable, rugged, waterproof
The reasons become clear after reading this:
- No fogging up on the lenses - as the glasses are filled with dry nitrogen
- Center focus - means you can adjust each of your eyes individually to a certain distance, means clearer viewing
- 90% light transmission - meaning almost all the spectrum is being used to enhance your vision
- Increased ability to see at twilight and during night time
- Fully waterproof - and they float too!
- Integrated compass - quick bearings, made easy
- Variable field of view - from 350' to 1000 yards. Just adjust your eyes to the new distance using the center focus. Remember focus your right eye first then left
Leaving the dock knowing you've got these aspects covered means you can concentrate on the business of enjoying your boating!
Here is a short video presentation for you to watch:
Did you know about the 10% discount at West Marine right now?
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VHF Radio
July 2, 2009 by Chris Wethered
Filed under Boat Electronics And Nautical Navigation, Boating Safety And Marine Finance
When your out and about on the water
one of the things on your mind might be the VHF radio. If you are not able to monitor channel 16, a vessel might be in distress, within range, but you just didn't know about it. Transmission of information is at the heart of boating, always has been.
The channels are internationally recognized, providing dedicated transmission possibilities. The basic functionality of send and received, has over the years been adapted to all sea goers. The United States Coast Guard has sole access to at least four channels, commercial and non commercial share channels.
When coming into harbor or entering a new marina, for example, boaters need to contact the harbor master, in order to get a berth. As part of ones boating safety, being able to keep in contact, when in range is important.
Necessary gear at sea or inshore
The question is:
Are you looking for a reliable VHF radio?
Do you want the follow from your next purchase?:
- Durable
Tough, resistant materials are used to bring longevity
- Easy read buttons
So you can punch in the channel you need quickly
- Clear display
Identify which channel your on through the scratch resistant cover
- Waterproof
In case your handheld goes in the water, it floats too!
- Long battery life
Never worry about running out whilst on the water
- Quality sound
No distortion means lower volume
Now watch this video presentation on a leading product
Take advantage! West Marine are offering a 10% discount, when you spend over $100!
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