What size prop and pitch

[oldfarmer4]

In process for changing OMC cobra 4,3 liter over to a SEI 116 outdrive. What size prop and pitch do I need?

 

[jimmbo]

Welcome to iboats

Like asking "I'm buying a Car, what do I buy?"

Are you replacing the engine too, or are you attempting to attach an Merc Drive to the OMC?

 

[oldfarmer4]

Conversion to SEI outdrive from OMC not replacing engine which is 4.3liter V6. I am thinking a 15/17 prop.

 

[harringtondav]

The drive reduction ratio is the key bit of information needed.
Also prop pitch on your OMC is important.
What ratio is in your OMC? What ratio is in the SEI drive you're considering?
If they're the same or very close, use the same pitch on the SEI, assuming you're OK with past performance.
Engine rpm divided by drive ratio = prop rpm. (4600 engine rpm/1.83 drive ratio = 2514 prop rpm).
Prop rpm x pitch = inches forward per prop rev.
You need the above info to solve your puzzle.

 

[Scott Danforth]

what was on the OMC drive. start there.

 

[Scott06]

I

The drive reduction ratio is the key bit of information needed.
Also prop pitch on your OMC is important.
What ratio is in your OMC? What ratio is in the SEI drive you're considering?
If they're the same or very close, use the same pitch on the SEI, assuming you're OK with past performance.
Engine rpm divided by drive ratio = prop rpm. (4600 engine rpm/1.83 drive ratio = 2514 prop rpm).
Prop rpm x pitch = inches forward per prop rev.
You need the above info to solve your puzzle.

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