When the boat was out of the water I carried out full underwater measurements. These along with engine power gear box ratios and shaft diameters were shopped around to various propeller companies for advice. I answered all questions and each company suggested a four blade propeller with more pitch and a larger diameter.

We were running three blade 20 inch diameter with 17 Inch pitch.

I decided to go with Finnscrew who recommended the smallest size propellor from all the responses and were also local to us in SE Asia. Their recommendation was 23 inch diameter 19 inch pitch four blade propellor.

With heart in mouth we measured the pitch, key way and sent the order away along with our deposit. The propellers were manufactured and delivered on time.

As we were replacing the propellers we decided to pull the shafts, replace the cutlass bearings and the shaft seals.

In for a penny, in for a pound. Quite a learning curve. Needed to manufacture a prop puller which we also used for seating the new bearings. Lots of sweat and swearing and the job was done. Fitting the new propellers was relatively easy. Just a touch on the keys with the angle grinder and on they went.

Sea trials weren’t as we expected though. Discovered both engines and shafts required re aligning. Back into the marina and a call to our mechanic Kumar. Two days later trials again. This time happiness.

In good conditions 1200 revs gives 7.5 knots and 1100 revs 7 knots. Trade off with increased boat speed for given revs fuel usage is no greater and possibly better at lower revs. We are still monitoring at time of writing.

FOR SALE!
2 awesome props

3 blade 20″ diameter with 17″ pitch