Going to a shorty = changing props ?

[farmo83]

So if I put a short on my boat and change nothing else, do I need to go up a size on prop ?

 

[Trash]

So if I put a short on my boat and change nothing else, do I need to go up a size on prop ?

Potentially, or prop design (i.e. Bravo 1 to something else).

Having said that I would start out with your current prop and go from there, otherwise you would be chasing variables.

 

[96motorhead]

When does running a shorter drive improve performance? How would someone determine if a shorty drive would help their boat?

 

[Croz]

Is a shorty drive like the imco ones with the raw metal look? I assume they reduce drag, if so how much? Worth it to do after a repower?

 

[Headless hula]

It has to do with better leverage, more than the different shape reducing drag. It has less drag because there's less drive in the water.

 

[farmo83]

So I have an RT and have been told by Lee and BD marine that a shorty would really wake my boat up performance wise. I've been nervous as in the past I've read about a shorty can cause planning issues and I enjoy pulling skiers, tubers, etc and didn't want to sacrifice here as this is where most of my time is spent as opposed to a few blast at WOT. After talking to BD he advised that the drive is set really deep in the RT and the hull could actually use a -3 or 4 inch shorty drive, so a -2 should be fine. Also that pulling skiers would not be an issue at all.

I get it having less drag and I believe it has better leverage as I've read multiple places that it does, I just don't get conceptually as to add leverage I would think you would need to lengthen something I.E. using a longer wrench to add leverage to loosen a bolt.

 

[96motorhead]

It sounds like you just need to try a shorter drive to see what it does. I've been researching shorter drives a lot lately and what I've found is you usually have to use a 4 or 5 blade prop and you need a pressure regulator because the short drives produce an average of 15psi more water pressure than a stock mercruiser drive. I also read that if you can run a 3 blade prop and if your boat doesn't cavitate at all then you can usually run a -2 drive. I don't know how true this information is, I just found it from looking online during some spare time.