2003 Merc 40hp efi 4stroke Prop ?

[deepsea]

I bought tis motor without a prop.(13 spline-2.0)I would like to know what prop came stock with this motor?I would also like to know what prop would work best on a 16ft trihull boat with this motor.Thanks for your time.

 

[Silvertip]

Re: 2003 Merc 40hp efi 4stroke Prop ?

I assume this is not a "Big Foot" motor? I would normally suggest a 11 x 13P but since you are talking about a 16 foot tri-hull, I assume this is a glass boat and therefore heavy. In that case I would suggest you try a 11 x 12P. You are asking a lot from the engine on that boat (if its glass).

 

[deepsea]

Re: 2003 Merc 40hp efi 4stroke Prop ?

Yes it is a glass boat.And I believe its a 15 footer. Will that size prop hurt the motor at all? I had a 50hp evinrude on the boat before and it moved the boat very well. What about a 4 blade ove a 3 blade prop? thanks

 

[Silvertip]

Re: 2003 Merc 40hp efi 4stroke Prop ?

The difference between 50 HP and 40 HP is 20% so you don't have a valid comparison. You also went from a two stroke to a four stroke so you will lose additional hole shot. The Evinrude was also geared differently so it could spin a bigger prop. A 50 HP Merc two stroke on that size boat typically runs a 13P prop. You can hurt the engine two ways: 1) by lugging it (too much pitch) or 2) over reving it (too little pitch). You need either a 12 or 13P in my view. With no other data to go by, you can only buy one and try it. Prop selection is trial and error when it comes to fine tuning.