Dufour 3800 - what engine originally?

[Almayer]

I have now in my Dufour Perkins Perama M20. There was originally Volvo-Penta, but I'm not sure which model and what power.
I want to know that, because I think about changing propeller. Now I have two-wings propeller, and I think about three-wing propeller. IMO it could be more efficient during more difficult weather and predictable during manoeuvres in marina.
Below link to photo of my propeller:

propeller Dufour 3800 - Cruisers & Sailing Photo Gallery

[skipmac]

If you look at used Dufours for sale most of them show a Volvo MD7B installed, at least on the 1982-1084 models I found. Sales specs showed 36 HP for that engine.

I did find one 1981 listed with a smaller 26 HP Volvo so their might have been different engine options from the maker.

[Almayer]

I have checked offers of used Dufours and I noticed that mostly they have MD7B. I wanted to be sure. Don't know why, but I thought she had originally 7.5hp volvo-penta.
Anyway, do you think changing propeller to three wing will bring me any benefits? If yes what parameters propeller should I choose?

[Cheechako]

3 blade props are often a lot better for powering through chop etc. also for reversing at the dock.

[Almayer]

Exactly. When I start to reverse, boat is not moving back, but rotate.

[skipmac]

The rotation is called prop walk and is usually more of a problem with two bladed propellers. Moving to a three blade should reduce that some and give you much more power in reverse. But you will lose a little speed under sail with the added resistance of the three blades.

Choosing the correct size can be tricky, part science, part guesswork and a little trial and error. You might check with what other owners are using. If you can't find any feedback that way you can use this online calculator to get you in the right range for your boat.

Vicprop - Prop calculator for Displacement and semi-displacement hulls

[Almayer]

Thanks for advice. I will have time to think about it during winter.

[Almayer]

Table with Dufour 3800 specification:
DUFOUR F31 3800 sailboat specifications and details on sailboatdata.com