How far down from top of transom

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How far down from top of transom

Postby Barrett81 » Tue Dec 31, 2013 9:15 am

Hey everyone been reading y'all's stuff for a while but finally goin to post. I have searched and can't font the answer I need. I am trying to build a surface drive similar to a copperhead. Where does my drive shaft/prop need to sit in relation to the top of my transom?? Again I'm new at this and have never ran a surface drive so if y'all need more info please tell me also if there are some links to this please send em my way.
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Re: How far down from top of transom

Postby mudpack » Tue Dec 31, 2013 12:11 pm

More important is where the prop sits in relation to the bottom of the transom; if the center of the prop is approx. even with the bottom of the hull, it will be about right for making fine adjustments with trim.
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Re: How far down from top of transom

Postby Barrett81 » Tue Dec 31, 2013 2:16 pm

Thanks that is kinda what I was needing to know!! That gives me a real good starting place I can defiantly work with that
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Re: How far down from top of transom

Postby Boatman » Tue Dec 31, 2013 4:33 pm

Thus the term surface drive. The moving surface will change depending on the speed of boat and how much the water rises after leaving the back of boat while on plane.
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Re: How far down from top of transom

Postby mudpack » Tue Dec 31, 2013 8:51 pm

Boatman wrote:The moving surface will change depending on the speed of boat and how much the water rises after leaving the back of boat while on plane.

'xactly!! :thumbsup:
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Re: How far down from top of transom

Postby GMag10 » Thu Jan 02, 2014 12:10 pm

Other important parts are the outdrive length and lower drive gear diameter. The bottom of your belt housing should be 3-4 inches above the bottom plane of the boat. If you are running a 6" diameter bottom pulley, that moves the centerline of the the prop shaft up another 4 or so inches. A longer outdrive will be able to compensate for this and keep the thrust as parallel as possible. I have been using a 30" outdrive on my builds.

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Re: How far down from top of transom

Postby GMag10 » Thu Jan 02, 2014 12:44 pm

This was my last build. 16 hp Duromax. 10X8 Hill Marine surface piercing prop. 1.5:1 reduction, Gates timing belt set up.
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Re: How far down from top of transom

Postby mudpack » Thu Jan 02, 2014 8:46 pm

G, how much to build me one of those?
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Re: How far down from top of transom

Postby GMag10 » Fri Jan 03, 2014 12:05 pm

Sorry mudpack, not getting much time in the shop this winter, but I will gladly help you through the design and build of one.

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