robeverton
New Member
Again, thanks for all replies and comments.
Latest - Engine compression etc checked and all within manufacturers tolerances. injectors all working.
Since cleaning out fuel pipes, replacing filters, turbo, exhaust manifold and exhaust mixer elbow, the engine will now hold maximum rpm at 3200 in neutral and without load.
When in forward gear and with very little weight in the boat, full throttle is only 2600 rpm giving a speed of 13.5 Knots.
As I mentioned, the previous owner changed from the standard 19 x 18 RH prop to a 18 x 17 RH prop because he needed to deal with quite strong tide runs in North Devon.
Now I appreciate that M in post *10 stated 'since you have a smaller propeller' but I'm not so sure it is that much smaller. 1" less in diameter and 1" less in pitch and but now with 4 blades. A lot heavier and needing a lot more grunt to spin up I would think. I don't know anything about cupping, blade shape, slippage etc, but to me there are now 4 blades of a similar shape and size to those on a 3 blade.
On my previous boat, albeit with an outboard, I changed from a 3 blade to 4 blade, and was advised to go down 1' in diameter and 2 inches in pitch. I noticed quite a drop in top speed but a much faster and stronger hole shot which suited me at the time.
I am leaning more and more towards replacing the prop with a standard 19 x 18 3 blade.
The manufacturers state that the boat should cruise at 13.45 kn @ 2400 rpm and max out at 17.5 kn @ 2800 rpm with the standard prop.
On a similar note if anyone has a 19 x 18 RH prop, bore 30mm x 1:10, keyway 8mm x 3.5mm ...... ?
Comments/reassurances welcome!
Latest - Engine compression etc checked and all within manufacturers tolerances. injectors all working.
Since cleaning out fuel pipes, replacing filters, turbo, exhaust manifold and exhaust mixer elbow, the engine will now hold maximum rpm at 3200 in neutral and without load.
When in forward gear and with very little weight in the boat, full throttle is only 2600 rpm giving a speed of 13.5 Knots.
As I mentioned, the previous owner changed from the standard 19 x 18 RH prop to a 18 x 17 RH prop because he needed to deal with quite strong tide runs in North Devon.
Now I appreciate that M in post *10 stated 'since you have a smaller propeller' but I'm not so sure it is that much smaller. 1" less in diameter and 1" less in pitch and but now with 4 blades. A lot heavier and needing a lot more grunt to spin up I would think. I don't know anything about cupping, blade shape, slippage etc, but to me there are now 4 blades of a similar shape and size to those on a 3 blade.
On my previous boat, albeit with an outboard, I changed from a 3 blade to 4 blade, and was advised to go down 1' in diameter and 2 inches in pitch. I noticed quite a drop in top speed but a much faster and stronger hole shot which suited me at the time.
I am leaning more and more towards replacing the prop with a standard 19 x 18 3 blade.
The manufacturers state that the boat should cruise at 13.45 kn @ 2400 rpm and max out at 17.5 kn @ 2800 rpm with the standard prop.
On a similar note if anyone has a 19 x 18 RH prop, bore 30mm x 1:10, keyway 8mm x 3.5mm ...... ?
Comments/reassurances welcome!