Out Island 41 Prop Size?

[DeepInIt]

Have one coming in the yard with no prop. Its a popular enough boat. Does anyone have prop size info? Based on a calculator and the prop shop, sounds like an 18X3 would work? Has Perkins 4.154.

[Captsteve53]

Well thats a 64 million dollar question but thankfully the following on line link should give you a pretty close answer if filled out precisely as

https://www.vicprop.com/displacement_size.php

Have used this link and is actually pretty correct every time, there are other on line calculators as well so easy to double check,

Just to be clear your propeller has three things to consider

1) Number of blades (blade shape required)
2) Pitch of Blades (EG. 13" pitch means theoretically travel 13" for each revolution) (but slip/bad design etc can change this slightly)
3) Diameter of Prop remembering tip clearance to hull is required

Cheers Steve

[dwedeking2]

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[EWOL Props]

Originally Posted by DeepInIt

Have one coming in the yard with no prop. Its a popular enough boat. Does anyone have prop size info? Based on a calculator and the prop shop, sounds like an 18X3 would work? Has Perkins 4.154.

You can have an idea of your prop size by using our Online Prop Calculator here>>> Calculate your propeller

Just be careful to input the actual data of max power at max rpm and gearbox ratio

[Cadence]

Originally Posted by Captsteve53

Well thats a 64 million dollar question but thankfully the following on line link should give you a pretty close answer if filled out precisely as

https://www.vicprop.com/displacement_size.php

Have used this link and is actually pretty correct every time, there are other on line calculators as well so easy to double check,

Just to be clear your propeller has three things to consider

1) Number of blades (blade shape required)
2) Pitch of Blades (EG. 13" pitch means theoretically travel 13" for each revolution) (but slip/bad design etc can change this slightly)
3) Diameter of Prop remembering tip clearance to hull is required

Cheers Steve

Slightly is an understatement as far as slippage. Good or bad design plan on 40 to 60%.

[Scaramanga F25]

There were 2 different reductions gearboxes on the OI 41. Different model years. My OI 41-6 with 454 engine was about 3 to one, others may have been nearer to 2 to 1.

[Caliber40]

Michigan propeller will do the same thing over the phone if you prefer human input.

GG

[Captsteve53]

With reference of 40 to 60% slippage/cavitation , if this has been your experience I WOULD IMMEDIATELY sack your propeller designer/manufacturer and use the on link posted in future to get your propeller with in a few percent at the first attempt, > perhaps if reference was to casting one your self at home using a candle and wax paper/plywood but in the year 2017 things have changed with propeller manufacturing/design methods!!!

[Cadence]

Originally Posted by Captsteve53

With reference of 40 to 60% slippage/cavitation , if this has been your experience I WOULD IMMEDIATELY sack your propeller designer/manufacturer and use the on link posted in future to get your propeller with in a few percent at the first attempt, > perhaps if reference was to casting one your self at home using a candle and wax paper/plywood but in the year 2017 things have changed with propeller manufacturing/design methods!!!

There are a bunch of variables. I would say planning or displacement may be the biggest. It is a science unto itself.

[Scaramanga F25]

In my OI 41-6 with a 4-154 I had been propped for years with, if I remember correctly, a 17"X 13". Apparently that was designed for the 2 to 1 reduction gear.
I do not remember if a 18 in. diameter prop would fit in the aperture leaving the 15% clearance needed. Otherwise I would go for more diameter every time.
I bought, cheaply enough, a used prop. 17"X 17". What a difference now I had great reverse and considerably more forward thrust. Remember, I had a 3 to 1 reduction gear.
The slight downside was that I did consume more fuel but gained speed which what I really wanted. Before the prop change that engine never put out the power that it was designed for.

[Cadence]

Originally Posted by Scaramanga F25

In my OI 41-6 with a 4-154 I had been propped for years with, if I remember correctly, a 17"X 13". Apparently that was designed for the 2 to 1 reduction gear.
I do not remember if a 18 in. diameter prop would fit in the aperture leaving the 15% clearance needed. Otherwise I would go for more diameter every time.
I bought, cheaply enough, a used prop. 17"X 17". What a difference now I had great reverse and considerably more forward thrust. Remember, I had a 3 to 1 reduction gear.
The slight downside was that I did consume more fuel but gained speed which what I really wanted. Before the prop change that engine never put out the power that it was designed for.

The ratio between the pitch and gear ratio is about the same.