Degsy
New Member
HI can anyone help here ? I recently purchased a yanmar 12G and I am now wondering what would be the ideal prop for this engine ie size and left or right screw. This will be going in my 30ft sailboat. Thanks in advance. Degsy.
The Right Propellor
- Thread starter Degsy
- Start date
Tranona
Well-Known Member
Not enough detail here. Suggests you go on the following website www.castlemarine.co.uk and use their Propeller Calculator programme
Bobobolinsky
Well-Known Member
Surely your left and right screw is dependent on your gearbox. Lancing Marine have a prop calculation program. You need engine HP, gearbox ratio, boat length and shaft diameter
Jcorstorphine
Well-Known Member
Rough calculation
If your Yanmar has a 2:1 reduction box then I am sure you need a Right Hand prop, that is the prop will rotate in the opposite direct to the engine with the gear in forward.
Using two different programs and guessing your waterline length at about 27 feet and displacement of about 10,000 lbs with a 2:1 gearbox, the correct prop for your boat is a 13 x 11 with a 55% DAR but this is only for a guide.
You need to get accurate details of the actual engine gearbox as it could be anywhere from 1.5 : 1 up to 3:1 ratio, all of which will have an effect on the prop dimensions together with the waterline length and displacement of your boat.
You also need to see how much room you have between the shaft and the hull. A general rule of thumb suggests you should allow 10% of the diameter as the clearance between the tip of the prop and the hull.
Regards
If your Yanmar has a 2:1 reduction box then I am sure you need a Right Hand prop, that is the prop will rotate in the opposite direct to the engine with the gear in forward.
Using two different programs and guessing your waterline length at about 27 feet and displacement of about 10,000 lbs with a 2:1 gearbox, the correct prop for your boat is a 13 x 11 with a 55% DAR but this is only for a guide.
You need to get accurate details of the actual engine gearbox as it could be anywhere from 1.5 : 1 up to 3:1 ratio, all of which will have an effect on the prop dimensions together with the waterline length and displacement of your boat.
You also need to see how much room you have between the shaft and the hull. A general rule of thumb suggests you should allow 10% of the diameter as the clearance between the tip of the prop and the hull.
Regards
