change to fixed prop

[nathanglasgow]

Looking for just a little more poke from our Beta 13.5hp in our Dufour Arpege.At present the set up is a twin blade folding prop at least 10 years old which gives a comfortable cruising speed of 4kns in calm water.If engine pushed hard we see just over 5kns.Would a change to fixed two/three blade fixed prop give any meaningfull increase in thrust(aware that performance under sail will suffer with fixed prop) but a little extra when motoring into wind/tide without having to max out engine would be nice.

 

[Tranona]

Lack of power is likely to be the main problem. Some folding props do have less thrust than fixed, but suspect you would have to go to a 3 blade for any significant improvement. Suggest you check out required prop size by puuting your boat's data into the Propcalc programme on www.castlemarine.co.uk

 

[alahol2]

Not really similar boats but similar weight and waterline lengths, our Beta 13.5 pushes the Stag 28 along at up to 6.5 knots max with a 2 blade 'skinny' prop. I would suggest you have the wrong diameter/pitch propellor.

 

[lw395]

Assuming the hull is clean, that really is poor performance.
When you say pushing the engine hard, does it rev hard, or is it making black smoke?
If you motor into waves or a headwind, does it slow down much? Do the revs fall off or does it smoke?

It may be that the motor is not making the power it should, perhaps a fuelling problem.
Or even a constricted exhaust?
I would want to be sure of this before changing the prop.