Distance between Arneson Drives?
 

Hi All,

Starting to hash out a build plan for my first HotRod go fast boat. It's a 33 foot V bottom with a pair of 500 HP engines and it will be running Arneson surface drives. The drives are an older set I picked up on ebay.

I'd like to run the drives fixed with a rudder. What I can't seem to find in any searches here is what the distance between the drives should be. Since it will have drive shafts I can put the drives anywhere. I'm thinking 20" centers should be about right. With the spacing of the stringers they could get as close as maybe 18".

Any recommendations?

First, lets start with which drives you have.

Second, the drives do not care what the center distance is

Third, what is your hp and speed goal? Might not benefit from this concern if the boat is not going fast enough to benefit from it in the first place

Fourth, what brand of V bottom and vintage?

Wow, that was quick. Didn't expect a response at this hour. Thanks :)
I'll answer your questions in the order asked.

1) I can post pics of the drives tomorrow for a positive I.D. I don't remember the exact model #. They're a 6 something. Not very good I know but, that's all I got right now.

2)I thought I read somewhere here that closer is better for tracking. If it doesn't matter then whatever is mechanically more convenient will take precedence.

3) Horsepower is 500 per side. Speed goal is 100+ for no particular reason. If it only hits 99 I'll keep working on it. If it hits 101 I'll run it til the props fall off.

4) This part gets tricky. Started out life as a 1979 26' Sleek Craft. When finished it will be 33' with a single step aft of the 26' part. Seems to freak people out a little bit when I tell them that. Hull weight is estimated to be 4500 pounds with 1/2 fuel.

Sleek, Rik is the guy to ask. He is everything Arneson. I would take all his recommendations/suggestions very seriously. He knows what works and what doesn't.

Well, since your goal is 100, then closer to the center of the keel will enable the propellers to keep a more constant supply of water. The closer the propellers, regardless of what they are attached to, the worst the close quarters handling will be as there is less mechanical leverage when trying to vector the thrust from port to stb. So there is a down side to a stagger setup as well.

500 hp a side and 33' is an ambitious goal.

Funny you started with a 26' Sleekcraft as we had several of those back in the day with a turbo charges 468 that would run 100.

Gonna need to see what model you have or can get and then it will dictate how things go forward from there.

Hey Rik,
Thanks for advising on this. I already have the hull and it is the Ambassador model.

Not sure I understand why 500 per side is an ambitious goal. Now days that kind of power seems conservative.

I did take a picture of the surface drive, just need to figure out how to attach it. Can I post it directly or is it better to link to a photobucket account?

http://i32.photobucket.com/albums/d5...g?t=1407269549

Here's a picture of one of the two drives I picked up. Naturally I'll go completely through them before installing.

The reason for my opening question has to do with the use of a rudder. While closer drives are better for speed I'm thinking maybe too close is not good either as it will disturb the flow of water to the rudder. Single engine boats do have a rudder directly behind the prop of course. My thought on this was by providing some optimal separation of the drives a cleaner flow of water to the rudder is possible thereby improving efficiency and allowing a smaller rudder.

Maybe I'm over thinking this. Thoughts?

Your weight might be off - a sleekcraft 28' enforcer -single 502 - dry weight is 4500lbs

I'm curious to see how your hull turns out. I was thinking about something like this last night. Is your step gonna be perpendicular to the chines or angled towards the back? How are you making your entension? The back of another boat?

You might be right although my estimate should be pretty close. The factory brochure claims 3500 Lbs with a SBC and Alpha drive. The intent is to build a very light and minimalist boat. I don't plan on having a fully equipped galley and built in furnishings etc...
I think the estimate should be close as the boat was weighed before I yanked out the old engine and Alpha drive and started replacing all the wood. Once I get to a solid, clean hull I'll weigh it again to have a good starting point.