4 blade prop

[Okydowky]

Took a while to configure the prop diameter and pitch but I think I found one we will be able to work with.
Question now is Overseas or American made? Bang for your buck?

Any thoughts or experience on over seas metals and workman ship? Other than costs is the most noticable difference right now.

I have had issues in the past with nuts, bolts and other overseas deck hardware not lasting. My gut is telling me no, but the prop shop obviously is saying they have had good results.

 

[fgarriso]

You may want to look at this calculator.
https://vicprop.com/displacement_size_new.php

 

[Choices]

A prop screws through the water.

For a single revolution, the boat screws a distance.
The size of the blade is your traction. A big sportfisherman may go 40" per revolution, and take 1000 hp to do it. And he turns it fast, maybe 1:1 or less, 2500 rpm.

My Lehman turns I think 23" and takes probably 40 hp. I turn it 400rpm, similar to yours.

I have a prop with 1" more screw. At the same rpm I get a 10% speed increase. 7 mph to 8. Takes slightly more fuel, which makes sense.

 

[Okydowky]

Taiwanese or North American

Has anyone had experience with Overseas props? Right now I got a price for the props I think we need and it was quite reasonable, but found out they are coming from Taiwan.

I get from fellow boaters! "hell no" "cheap is good". I am not sure what there quality would be like, I have had some experience with poor over seas quality products before.

 

[fgarriso]

Has anyone had experience with Overseas props? Right now I got a price for the props I think we need and it was quite reasonable, but found out they are coming from Taiwan.

I get from fellow boaters! "hell no" "cheap is good". I am not sure what there quality would be like, I have had some experience with poor over seas quality products before.

I ALWAYS stick with US made props. They seem to be better balanced, and stronger.

 

[PM]

I read someplace that every time a prop blade comes close to a part of your boat there is an "incident". A very minor occurrence between the water, bubbles and the hull of the boat. With a three bladed prop, you get three of these "incidents" per revolution. If you have a full rudder like on a single screw trawler you would get six of these "incidents" per revolution.( Three against the hull, three against the rudder support of the keel.)

With a four bladed prop, you would get four of these "incidents" per revolution, eight with a full keel.

With a four blade prop the "incidents" would happen top and bottom at the same time as one blade passes near the hull and its opposite blade passes near the keel.

These so called "incidents" are minor, tiny events. (If they occur at all) But taken cumulatively it equals nearly a million "incidents" an hour at 1800 rpm, Several million an hour in a high reving go fast boat.

If an "incident" has no more effect than a tiny air bubble hitting a prop blade or a tiny drop of water hitting the hull or whatever tiny comparison you can imagine, multiplied by several hundred million on a cruise it really could contribute to prop noise, vibration or some other disturbance.

Of course, I have no idea if there is anything like this self described "incident" but it is food for thought.

pete

 

[BruceK]

Most Taiwanese boats likely had Taiwan props, that`s a lot of props. I found Taiwan made boat stuff better than their immediate neighbour`s,eg. anchor windlass switches. Unless politico/economic reasons matter,if price is much better and availability good,choice seems clear.

 

[Nomad Willy]

Pete,
I believe such “incidents” do in fact occur.

But I also think these occurrences happen so as to make a 4 blade about as smooth as a 3 blade and visa versa. But the blade tip design, mostly the width of the blade tips will make a 3 blade less efficient than a 4 blade. There’s lots of little variables that cancel each other largely out.

So when choosing a 3 blade or 4 blade most or all of these “incidents” should be overlooked. Just choose the number of blades to achieve optimum blade loading and a good balance of pitch/dia. ratio. To not have too much pitch or diameter is far more important that anything else.

 

[FF]

"Question now is Overseas or American made? Bang for your buck?

Very pleased with Ahoy props, price and quality.

Taiwan workmanship seems far better than mainland communist products.

Ahoy Propellers | Inboard Boat Props | Stainless Marine ...

www.ahoypropellers.com

Ahoy Propellers provides quality propellers at affordable prices. Our inboard boat props are engineered for superior performance, durability and...‎About Us · ‎Ztrack Props · ‎Torking Props · ‎Our Process

 

[PM]

Probably "Overseas or American made" could be another thread which would get plenty of play. But..since you asked:

The cost to ship a boat from Taiwan, or China or Italy would probably be about a quarter of the new, retail purchase price. So before we can talk quality of parts, workmanship and labor, building techniques, etc. we need to consider final price.

A boat which is overpriced just will not sell. By overpriced I mean comparing apples to apples, not comparing a Mainship to a K.K.

pete

 

[sunchaser]

Our vessel when new came with Chinese props. The prop engineering and spec sheets for the props were part of the design package. This package and the 4 blade props have been spot on for 15 years and trouble free.

Taiwan and China have been in the marine heavy metal business for a very long time. Anyone know where Fleming, Outer Reef, Nordhavn etc props are made?

 

[Okydowky]

Very true there are hundreds and if not thousands of Tai Tubs running around 40 or 50 years later with the same props. So at some point there had to be quality built parts.

But than again even in our own countries today things are built to throw away in a few years, it's a disposable life we live in now.

My parents said for years when I was growing up "things are built like they used to". Well now that I am up in years I get it!
Things aren't built at all like they were 50 yrs ago, like grammas waffle iron and blender. The list could go on and on.
Other than the reduced cost of overseas merchandise, not sure on quality these days. I guess if your local reputable prop shop will back up there products they sell you, that's all you got!

 

[Okydowky]

Did you say Fleming!!

Not sure if the picture will attach, I will try. Found this little tub down the road from our boat. At 78' it's quite impressive to see out of the water.

Now if I can get a couple props like they got from Taiwan, I am in… I was told each prop cost $50K with the option of the 2 under water cameras pointing at each prop.