Help with New Prop Decision!!

[Beardyallan651]

Hi Guys,

I have a stroma yawl, outfitted few years back. I have now fitted a new gearbox and damper due to slippage only to find that gearbox was running opposite with left haded prop. I now have new gearbox fitted and would like to fit right-handed prop. Engine is a 3 cycklinder Kubota fitted with ZF10 Gearbox. Boats 6m .

Im curious about the pitch needed, its fitted with a 14inch diameter prop.

Cheers

Allan

 

[srm]

If you google "boat pitch calculator" you will find some on-line calculators. These will give a starting point but you also have to allow for the power of the engine. Number of blades and area also comes into the equation. Too much pitch and the engine will not be able reach its rated RPM. A specialist supplier should be able to help match a prop to the boat and engine installation.

Nice looking boat but why is she flying international code flag "M" = my vessel is stopped and making no way through the water?

 

[RobinBirch]

Have a look at the Betamarine site ( marinised Kubota base) It has a prop selection guide. Might be a useful reference for a sense check.

 

[scottie]

If you google "boat pitch calculator" you will find some on-line calculators. These will give a starting point but you also have to allow for the power of the engine. Number of blades and area also comes into the equation. Too much pitch and the engine will not be able reach its rated RPM. A specialist supplier should be able to help match a prop to the boat and engine installation.

Nice looking boat but why is she flying international code flag "M" = my vessel is stopped and making no way through the water?

Saltire not M
it’s only M outside Scotland unless is a temporary racing mark

 

[Sandy]

Contact any of the prop manufactures with your needs and they will calculate what they will sell you.

 

[LittleSister]

Saltire not M

No, it looks the wrong shape for Saltire -

M


Saltire

 

[DoubleEnder]

Have a look at the Betamarine site ( marinised Kubota base) It has a prop selection guide. Might be a useful reference for a sense check.

Definitely do this. The variables are hull shape, engine SHP waterline length, displacement, gearbox reduction ratio, prop. aperture. Beta marine website will be a start, then look at some other online calculators. I have used Castle Marine - Pitch Calculations
but there are many others.

 

[srm]

Saltire not M
it’s only M outside Scotland unless is a temporary racing mark

The official Saltire is a lighter blue than in the photo, (as per Little Sister's post) as any true Scottie should know. The only reason that the saltire in the union flag has a dark blue background is that in 1707 flag makers could not produce the correct colour dye in sufficient volumes. You will also find that the Shetland flag uses the saltire blue; not navy blue as in the union flag and the code flag.

 

[scottie]

The question was why was she flying this flag and whilst you may be technically correct I can assure you it is intended to be a Scottish flag in this case as is the one painted on the side of the boat

 

[westernman]

If the pitch is not quite right, you can always get it adjusted.

Specialists now how to do this and it is not expensive. Just tell them what rpm you reach vs max rpm for the engine if over pitched, or the that you reach max rpm at x% throttle for and they will know how to work out how much pitch to take off/put on.

 

[stav]

I would second the getting pitch changed. When I changed my gearbox I tried a secondhand prop then back to the original having the pitch altered twice. FAL propellers in your neck of the woods gave excellent service with a quick turn around.

 

[Daydream believer]

The question was why was she flying this flag and whilst you may be technically correct I can assure you it is intended to be a Scottish flag in this case as is the one painted on the side of the boat

Then one might ask why it is not being flown from the stern?

 

[scottie]

Because there is a version of the red ensign with a saltire replacing the union flag (not legal)

I am suggesting the possible rational behind the use not condoning it.