Will a High-Speed Prop Work on a Sailboat ?

[chris07732]

If you think your boat is over propped now, why do you think the same prop, but with "super cupped" is going to be better. Cupping a prop has the same effect as increasing the pitch. It will create more "bite" in the water for a given RPM. If you're "lugging" the engine now, going to the super cupped prop will drop your RPM further.

[Play Actor]

We ran the same engine/trans on a similar boat (Baba 35)for 20 years. A standard 16 inch x 12 inch pitch prop worked out right -- we hit max rpm of around 2700 at hull speed, and cruised at 5.5 -5.8 knots at 1800 rpm. Note, you probably need a left hand prop.

16x14 will almost surely be overpropped.

[bazzer]

Originally Posted by Play Actor

We ran the same engine/trans on a similar boat (Baba 35)for 20 years. A standard 16 inch x 12 inch pitch prop worked out right -- we hit max rpm of around 2700 at hull speed, and cruised at 5.5 -5.8 knots at 1800 rpm. Note, you probably need a left hand prop.

16x14 will almost surely be overpropped.

Thanks for a excellent reply, the current prop is something like 18 x 16 LH which the PO has fitted, Michigan Prop recommended a 16 x 14 , but what you say makes a lot of sense. Funny thing is, a friend of mine with the same motor in a 32 ft Ficher has the same problem, but he has a different gear ratio.

[Play Actor]

We just repowered because I couldn't get parts for the old Volvo transmission. Michigan wheel recommended a 16x14 for the new engine/trans as well. It runs the shaft at roughly the same speed. (Yanmar 3JH5E, 2.33 trans ratio). We had to buy a new prop because of the RH rotation, so switched to a 3 blade Campbell Sailer, 16x10. It's great. Less drag under sail, more efficient, a little cheaper than the Michigan Wheel 3 baldes.

If you have to buy new, take a look at it, and trust their recommendation if you decide to buy. They hit it on the nose, first time.

[fstbttms]

Originally Posted by DeepFrz

Oh, go ahead, just buy it. Let us know how it works out.

Bwahahahahaha!

[limejucer]

Iv got an old ford and the gear box is sloppy. I can get a bargin F1 gear box should i buy it? It will be ok and save me money.
Same question the prop should be matched to the drive for efficent operation. it will turn and move some water in what direction?

[bazzer]

Originally Posted by limejucer

Iv got an old ford and the gear box is sloppy. I can get a bargin F1 gear box should i buy it? It will be ok and save me money.
Same question the prop should be matched to the drive for efficent operation. it will turn and move some water in what direction?

I'd put in the F1 box, they are really small, shift in a fraction of a second and are rated at more than 700hp. Each F1 team uses each gearbox for at least three races, plus it would have a very high resell value.

[bazzer]

I was just trying to find out the difference between a sailboat prop and a high speed, not surface running, prop.

[Marksman]

High speed props are sized and piched for HP and speed through the water. The limiting factors are tip speed (RPM and cavitation) and HP dictating maximum pitch. The faster the desired boat speed, the greater the pitch needed at the limiting RPM.
Displacement hulls have different requirements as boat speed is not a suggnificant factor effecting pitch. For that application greater diameter and lower pitch has it's adventages. This allows a lower HP motor, geared down to spin a larger wheel. The tip speed is not excessive because of the lower rpm and the pitch can be lower becuause of lower hull speeds taking better advantage of the available HP.

Someone else can probably explain it better but that's it in a nutshell.

[Celestialsailor]

I bought a prop on ebay, old new stock for $125 w shipping. It is a 17-14. I would wait and get something closer

[perchance]

Trade the prop you have for the one you want. Failing that sell it and put the money into a new prop.