Going from 1996 mercury 40-HP to 2003 40-HP mercury big foot

[huffduf41]

Hey guys this is probably a dumb question but I changed the outboard on my pontoon and need to reprop it. If it was propped perfect with my 1996 2-cycle mercury 40-HP will the same pitch/dia work with the 2003 four stroke 40-HP Bigfoot?

Thanks!

 

[Sea Rider]

Re: Going from 1996 mercury 40-HP to 2003 40-HP mercury big foot

Was the old model a 2 strokes ? Assume propped perfect was using a tach, right ? Check if both 40's has same wot parameters. In any case must re check wot rpm with new model and factory delivered prop just to be sure you will run inside safe wot rpms.

Happy Boating

 

[jestor68]

Re: Going from 1996 mercury 40-HP to 2003 40-HP mercury big foot

Use the Mercury prop selector to get in the ball park.

Your 4 stroke has a different rpm range( 5500-6000 rpm) than your old 2 stroke, and the big foot uses the same larger diameter props as the Mercury 75,90,and 115 motors(up to 14" dia).

The larger diameter props should do a better job of pushing any pontoon boat.

As an example; if I run a 22ft pontoon through the Mercury prop selector with a 40 hp 4 stroke bigfoot, it gives me a 14 X 10 or 14 X 9 aluminum prop.

Engine tests on the Mercury web site indicate the a 40 4 stroke big foot pushing a 20-22 ft pontoon boat are doing about 5900 rpm @ 18 mph with the 9 pitch, and about 5500 rpm @ 19 mph using the 10 pitch aluminum prop(14" dia).

I would go with the 14 X 9 Black Max/Quicksilver Black Diamond; or Solas for less $.

 

[huffduf41]

Re: Going from 1996 mercury 40-HP to 2003 40-HP mercury big foot

The prop that was perfect on the 2 stroke was 11.25" dia with a 10" pitch. Thanks again for all the help guys.

 

[huffduf41]

Re: Going from 1996 mercury 40-HP to 2003 40-HP mercury big foot

The pontoon is 24' if it matters. Thanks