Question about Prop diameter vs pitch

[reelhappy]

Looking for some direction on a starting point for a prop. I am installing a 50hp Merc on a 17" Scout CC and have a question as to which is better a larger diameter with less pitch or a smaller diameter with more pitch. I have looked at 12"x10"p and 10.5" x14"p. I not counting on getting the perfect prop first time but would like to know which diameter to start with and then I can fine tune the pitch. Thanks

 

[steelespike]

Re: Question about Prop diameter vs pitch

What 50 Merc are you running?
If there is a prop on it run it and see what it does.Generally a larger diameter
lower pitch is for a heavier type boat/load.Your 50 is a little small for a 17 footer.My 65 Merc 500 I think has an 10 3/4 X 11 on a 330lb.18 ft Crestliner utility W tiller steering. Your Scout is signifigantly heavier.

 

[reelhappy]

Re: Question about Prop diameter vs pitch

Thank you for the response. The motor is a 2001 Merc 50hp 2 stroke and you are correct it is a little under powered but need to make due with what I have. I do not have a prop at all to start with so I am at a loss. Boat weight is 1400lbs with motor and gear. Thanks Again

 

[Silvertip]

Re: Question about Prop diameter vs pitch

10-1/2 x 13P is fairly standard for that engine on boats to about 16-17 feet. If it's a lightweight boat, perhaps a 14P or 15P will do. Larger diameter props are typically used on the bigfoot engines that have 2.33 gears. Your engine has 1.83:1 gear set. Slight diameter changes (10-1/4, 10-1/2 etc.) have little effect on performance and is a prop design characteristic. Pitch is far more important.

 

[wca_tim]

Re: Question about Prop diameter vs pitch

Ask at the local shop(s) some have used props of various shapes and sizes they will let you try out. I recently went through trying about 9 different props, many from the local parts counter's wall of used ones. I bought one used and one new from them in the end... lots of places will work with you on that if you're a decent customer...