Propeller sizing?

poppajoe · 25-02-2006, 20:21

Does anyone know where there is one of those websites where you can get an idea of the prop size you need after entering certain data - I mean one of the one's that gives you an online solution rather than waiting for a working day reply? I used one once but have forgoten where it was...

**ChrisP** · 25-02-2006, 20:28

http://www.castlemarine.co.uk/shopfront.htm

Click on the Pitch Sizing link.

Warning ......it is only as good as the info you put in, very accurate if the info is spot on.

poppajoe · 25-02-2006, 20:38

Originally Posted by ChrisP

http://www.castlemarine.co.uk/shopfront.htm

Click on the Pitch Sizing link.

Warning ......it is only as good as the info you put in, very accurate if the info is spot on.

Hey, Cheers ChrisP, thats what I call a helpfull, speedy answer!!!

Thats better than the one I used before and I should have thought of them - I have used them twice to refurb my old jet prop and a damn good job they do to at reasonable rates I must say..

I need more info from the boat but when I get it I now have the solution.

Thanks again...

**Rohan** · 25-02-2006, 20:48

It would be nice is everybody with a boat chipped in with there motor and prop size.....

Ocqueteau 615, Yamaha 80 4 stroke emmm I will have to look

**ChrisP** · 25-02-2006, 20:51

Used to work there so I may have done them for you.

Rule of thumb each inch you increase the pitch decreases your engine revs by 200RPM and vice versa. If you know what prop you have and what you want your engine to be doing it can be handy for checking your calc to see if anything glarringly obvious is wrong.

poppajoe · 25-02-2006, 20:54

Originally Posted by Rohan

It would be nice is everybody with a boat chipped in with there motor and prop size.....

Ocqueteau 615, Yamaha 80 4 stroke emmm I will have to look

Hi Rohan,

Yur right that is a good idea - a databank for reference..

I have a Taskforce 18 (for a while) with a 60vro 3cyl Johnson - runs sweet as it could, 42mph flat out and cruises all day at 25mph with me and my son fishing gear and all.
I will post back with the correct size following next visit to the mooring as my memory may fail me..

**ChrisP** · 25-02-2006, 21:02

Just a guess.

Rohan 13 3/4 X 15
Poppajoe11 3/4X17

How close was I?

poppajoe · 25-02-2006, 21:06

Originally Posted by ChrisP

Used to work there so I may have done them for you.

Rule of thumb each inch you increase the pitch decreases your engine revs by 200RPM and vice versa. If you know what prop you have and what you want your engine to be doing it can be handy for checking your calc to see if anything glarringly obvious is wrong.

Hey what a small world - if it was you, it was a fine job anyway. It was a hamilton jet running on a 70hp wotamotor (or ford escort 1600 in my case) and they are fine until you put your boat on a muddy or sandy mooring, then you have to get it rebuilt every year like I did - still cracking job you did, it used to double the speed every year when fitted, that was some 4-6 years ago.

The Icelander I bought today is running realy slow (10 knots) and is obviously running with the wrong gears or prop on the volvo penta leg - it is revving to quick and easy for my liking and should do better for 65hp.

The bottom needs a bloody good scrub agreed, but you know when something is not right in my experience - still added to a scruffy boat needing some TLC (which I love doing) it kept the price way down and made it a cracking buy.

It will be back with me next week and all will be revealed.

Anyone wanna buy a Taskforce 18 in the coming weeks!!! (oops, sorry could not resist)

Cheers Chrisp

poppajoe · 25-02-2006, 21:14

Originally Posted by ChrisP

Just a guess.

Rohan 13 3/4 X 15
Poppajoe11 3/4X17

How close was I?

I don't mean endless, endless you know whoops?

I will post back chris and you have got me intrigued now too.

**blueskip** · 26-02-2006, 18:10

My 16' 6" Deep V planing hull (whatever it is), run like a dumper with a 50HP Merc, with an 11.25"dia x 14" pitch prop, it ran much better with a 10.75" x 13" composite, & runs even better with a 10.75" x 12" pitch! I have bought a 12" x 11"pitch which I will try on soon to compare.
There are so many variables regarding hull shape/finish etc that I think "suck it & see" seems to be the best solution!
blueskip