Houseboat Propellers - how many blades, material, for the best prop?
by Tim Conley
(Des Moines, Iowa)
Houseboat Propellers - best props for house boats?
Looking at houseboat propellers, how many blades, or what material, makes for the best prop? I was curious if anyone has dealt with this situation.
I have a 40' Crest pontoon houseboat with a single 90 h.p. outboard. When I reverse out of a slip, it takes a country mile to make any degree of a turn. When I move forward, the boat will turn on a dime.
It was told to me that I replace my 3 bladed propeller, with a 4 bladed prop, I would solve the reversing problem. Will one more blade make that much of a difference on the prop?
Any help is appreciated, Tim Reply - Answer
Well Tim, you have posted a great question that gets asked often amongst houseboaters everywhere, "what is the best propeller to put on a houseboat?"
One of the best props for houseboats are the RHC Propellers
since they provide better stopping, more reverse thrust, and improved handling.
Before we get into ways of improving the reverse performance on your houseboat, we have to look at what makes for the "right prop" on any boat. We have to remember that we are talking about a heavy, slow moving, non-planing hull, that have will always have less performance in reversing out of a slip.
Now will you see any real improvement in changing to a 4 blade propeller, personally I have never seen any real world performance difference when I have tested non-planing houseboats with a 4 blade model. Now your mileage may vary, but I think there is other things to look at first.
You should a good look at the present condition of the prop that you have now. Look at the surface and edge condition, and
see that it allows you to reach WOT?
And if we look at the material choice for propellers, stay with aluminum as it is easily and cheaply repaired, and doesn't cause as much damage should you touch the bottom :(
Now, if we start off by looking at the basics of what is involved in having the best prop on your boat, we have to understand what's really happening. The engine(s) has to be able to achieve the manufacturers recommended RPM (revolutions per minute) and WOT (wide open throttle) range. This is where you will gain the biggest performance, and handling improvements.
Here are some of the common propeller terms
you will be asked:
Diameter = This is the overall exterior size from the tips of the blades.
Pitch =The theoretical distance that the boat would advance in one revolution.
Blades = Most of the popular propellers are available in 3, 4, 5 blade designs.
Material = Aluminum, Stainless, Brass, and Composite materials are available.
WOT = The "wide open throttle" rpm of the engine with average load and people.
LH or RH = The most common is Right Hand rotation, but Left Hand is available.
Thru Hub Exhaust = A popular feature with many engine and outboard engines.
The most common problem that I have found in many houseboat propeller installations are that the prop is damaged, blades are dinged, or simply not the correctly sized propeller for the boat, load, and engine application. The correct propeller on a boat is vital and is the heart of the propulsion system.
After many years of personally playing with different props and blades, the simplest solution for displacement barge style, full hulled house boats has always been to put the largest diameter propeller, with the correct pitch to allow the engine(s) to reach the recommended WOT. EX: 4400 - 4800 RPM.
If the engine can't reach WOT, this causes
poor gas mileage, poor performance, and potentially damages the engine(s). I have seen many houseboats that have had serious engine damage, often causes by lugging an engine, with a prop with too much pitch.
You probably have heard many folks say that they will just throw a bigger pitch prop, because they will never rev the engine above 2500 or 3000 rpm. They presume that they will get better gas mileage and better performance, however the damage is being done even if your running at 1000, 1500, 2000, 2500, or 3000 rpm.
Personally, I would stay with your 3 blade prop, however I would do a little testing. You would first want to verify your engine manual, or read the specification sticker on the engine itself to see what the manufacturers recommended WOT range is.
On inboard engines, it could be in the 4000 - 5000 RPM range, and on outboards, will often be in the 5000 - 6000 rpm.
If you have access to a GPS, this is a great tool also to use while verifying the WOT as you can take note of the speed that you're achieving. You will be able to compare the speed now, with any changes you make to the prop.
Now, take the houseboat out for a ride, with a friend if possible, and in a safe location, on a relatively smooth lake, open up the throttles, and read how high that the RPM's go. If you have access to a digital RPM meter, have your friend read the figures directly from the engine itself.
If your houseboats WOT rpm is lower that the manufacturers recommended range, you will need to reduce the pitch of your propeller, @ 150-200 rpm per inch of pitch.
Don't let the engines to run higher that the recommended WOT range for more than a few seconds, and only long enough to see how much over and above the rpm is. EX: You're running at 4900 rpm, and the range should be 4200 - 4600, than increase the pitch by 2 inches. (2" x 150 - 200 rpm = @ 300 - 400 decrease)
So, to answer your question, should you spend your money on a 4 blade prop, not really, but do a little investigation into what you have now. I have also found that even though the propeller hub is stamped 16 x 11, and the propeller has previously been rebuilt, I would do a diameter and pitch comparison against a new 16 x 11 prop.
I have seen prop shops that rebuild damaged props, and they come out looking good, but they don't match the original specs.
If you damage a propeller, and decide to have it repaired / rebuilt, keep it onboard afterwards and use it as a spare, and only use it only till you buy a new replacement propeller. No disrespect to prop repair shops, it's is just that the good ones are getting harder to find.
When you consider the cost of a new prop, compared to the cost of having one repaired, it just isn't worth the risk of engine or drive damage and repairs.
Do some testing, and do let us know what the figures are that you find out, and share them here with us, as I am sure there are many other houseboaters who are curious.Lastly
, hopefully some of our readers will share and post comments about their houseboat propeller choices and experiences. Feel free to use the "Click here to post comments." link found near the bottom of this page.
Thanks again for sharing, IAN from all-about-houseboats
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