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Polishing Lower Drive Housing

Old 10-22-2020, 10:37 AM
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A=While looking for info on outdrives I ran across a few that people had taken the time to polish. It looks great, I have always been a polished aluminum kinda guy and want to do mine. I do know there has been an argument for years saying that polished parts increase heat due to surface area being less. I have polished a lot of engine parts and have never noticed anything worth mentioning as far as extra heat. I saw someone say that the polish is also gonna take top speed away on a boat. What do you think? Anyone done any testing with a boat in real world conditions to see? If the rough surface translates to a faster top speed, why aren't props bead/sand blasted instead of polished? I want to do my bare aluminum outdrive parts. I also have a stern jack that I can do. Any reason anyone can think of to not do it, other than the many hours of wasted time!?
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Old 10-22-2020, 11:30 AM
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Jumping on the "way back" machine, I worked for American Hot Rod when it was part of the RH Little company in '85/'86. Made little 10 & 15cui racing outboard engines. They were definitely faster with an "as cast" gear foot (lower unit). While on a much smaller scale it probably still applies.
I've often wondered if these things are still produced by anyone. I built the tooling for machining the gear foot from a raw casting.

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Old 10-22-2020, 12:32 PM
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I know that racing sail boats do something to the surface finish to rough it up for more speed. They say that a perfectly smooth surface sticks to the water and increases drag. I have noticed on my boat when the water is like glass that it porpoises terribly. It's like it sticks and then snaps free and sticks again. When I get a little chop it flies. Now that you mention it, I think I'm going to do something to my lower to rough up the surface and see what it does.
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Old 10-22-2020, 02:47 PM
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From the factory they are smooth
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Old 10-22-2020, 06:34 PM
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Smitty, those little boats look like tons of fun! Drock78, the as cast finish Smitty is talking about would be smooth to the touch but is nowhere near a polished finish. It probably still has enough surface roughness to break the water tension. I was thinking about it a lot today and was thinking about what Thisislivn was saying. His smooth shiny finish seemed to stick to the water. Well, I am a snow skier and a good wax job is not polished. It has texture provided by brushes. It is said it keeps the melting snow that turns to water from causing suction. Makes since a boat would do the same.I would have to assume some brilliant person at MIT or some other university has done some research on surface finishes for power boat racing. Has anyone looked into it? As much as I would love that baby to shine on the trailer, I really want it doing good in the water. Would there be a process like sandblasting that would give an optimal finish for speed/efficiancy? What about bottoms of the hull? Maybe a question to ask in the paint and cleaning section.
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Old 10-22-2020, 06:50 PM
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Old 10-22-2020, 06:52 PM
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