2 blade vs. 3 blade

[copeina]

Just bought a 1980 Merc 20 for my old boat. Everything works fine, but the spare prop the guy gave me is a 2 blade rather than the 3 blade that is on the motor now.

Any reason to use one vs. the other?

Thanks,
/Kris

 

[jimmbo]

Re: 2 blade vs. 3 blade

More info such as pitch is needed before an answer can be given. However, generally a 3 blade prop is less efficent than a 2 blade and will deleiver less top speed. The 3 blade though will offer better load carriing and be smoother than the 2 blade.

 

[Texasmark]

Re: 2 blade vs. 3 blade

Agree with jimmbo. Merc used 2 blades for a lot of years on their new (for sale) engines. The racing engines that the locals used were always 2 blade propped. I know the 20 hp Hurricanes were mighty fast with their 2 blade on a 14' fishing boat.....always outran me.

When I got into skiing, with 18-25 hp engines, we went to 3 blades for more hole shot and it seemed to work. I can't tell you anything about rpms or prop pitch....too long ago and no instruments at the time.

Course Johnny/rude had 3 for as long as I can remember and the only time they offered a 2 blade (as I recall) was bronze and only on a sport version of their 90 hp Meteor back in the early '60's....I think then). Their 25-35 hp engines could push mighty good with them.

They pushed a lot of boats with a lot of loads for a long time. Then about the Phantom Black Lacquer time (late '60's or early '70's) they shifted gears (changed philosophy) and came out with the 3. Been selling with 3 ever since.

Bout all I know about it....not much. Check with Dhadley if you really want to know.

Mark

 

[jimmbo]

Re: 2 blade vs. 3 blade

Merc offered 2 blade props on all their engines, with the exception of the v6s, up to and including the 1978 model year. In 1979 the engines, 40hp and above, had new lines of props with new blades shapes having more rake, of which very few were 2 blades.

BTW Tex, Phantom Black was intoduced in 1961 on the 1962 100hp Phantom. By 1963 or 64 the entire Mercury line was painted black