Feathering Propeller

[fstbttms]

Originally Posted by senormechanico

"A Maxprop is a very spendy item.

A new 2-blade for a saildrive will run you from $1750-$1975 U.S., depending on diameter.

[Ex-Calif]

Originally Posted by S/V Elusive

it wasn't an easy job getting all three blades on and in place, I'm a bit hesitant about having a diver do it - I'm screwed if something is lost or damaged.

We pulled the boat onto the ramp and changed the prop. It took two of us (4 hands) and I could not imagine doing this underwater. We didn't drop anything but I almost dropped on of the clamshells. Additionally, to remove the prop nut for the old prop we had to rig up a couple of 2X4s to get leverage on the nut. It would be tough to get leverage on that nut while neutral bouyant underwater.

Anyway, I set the prop up for about a 9 inch pitch. We backed down the ramp and I cautiously put it in gear. At idle forward I could immediately "feel" the pull. Not so with the other prop. I advanced the throttle to about 1600 and as the boat accelerated the engine speed also accelerated. I reckon this is a good thing as the engine is loaded until the boat accelerates. A little lower pitch would help acceleration but we aren't a drag boat. Anyway, it was thrilling.

Within a few seconds it stabilized at +6.5 kts and 2,000 rpm. At 2500 RPM we were probably at hull speed and could see and hear "cavitation" off the transom. Any throttle push past 2200 rpm would probably be like pouring diesel in the ocean for no speed change.

With the old folding prop we were getting about 3.5 kts at 2500 RPM.

Reverse performance was startling and I almost had the tiller ripped from my hands as the boat acelerated in reverse.

We were working against time as we had to get the boat out at high tide so the trial only lasted about 10 minutes. We'll do some better time trials when she goes back in next month but I suspect this swap to be a complete success. I think we will be able to motor at +6kts at 2,000 rpm, saving fuel, engine wear and tear and lowering noise levels.

I am totally stoked.

We bought the donater a $180 bottle of blue label and laser engraved our boat name on it.

[fstbttms]

Originally Posted by Ex-Calif

We pulled the boat onto the ramp and changed the prop. It took two of us (4 hands) and I could not imagine doing this underwater. We didn't drop anything but I almost dropped on of the clamshells. Additionally, to remove the prop nut for the old prop we had to rig up a couple of 2X4s to get leverage on the nut. It would be tough to get leverage on that nut while neutral bouyant underwater.

I have installed quite a few folding and feathering props singlehanded underwater and (knock on wood) have yet to lose a part. One of the tricks of the trade is to suspend a "safety net" under the business end of the shaft to catch anything that might drop. I can remove the existing prop and install a new Max Prop in about 2 hours. Once you know what you are doing, it is fairly straightforward and not particularly difficult.