DIY Painting Lower Unit
04-03-2012, 02:24 PM
#1
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DIY Painting Lower Unit
Painting your lower unit 
.....not this lower unit =====> 
LOL
What is the best way to prep & product to use for lower units? I painted a lower unit on an outboard of mine with zinc and then factory paint but it didnt last as long as it should have...
Was thinking of unbolting unit and lowering enough to just paint lower unit.
Also....nose cones I understand dont make much difference until 70ish+mph.....they do look sweet though! Anyone offer a nose cone for an alpha one that would require minimal mods to smooth out the units housing (ex. minimal fillers / smooth fitting)? I know Bobs offers one but not sure who else may offer....
Not in the 70+ (350ci 60+ish mph) but while painting, thought it would be the time to do one if I were...
.....not this lower unit =====> LOLWhat is the best way to prep & product to use for lower units? I painted a lower unit on an outboard of mine with zinc and then factory paint but it didnt last as long as it should have...
Was thinking of unbolting unit and lowering enough to just paint lower unit.
Also....nose cones I understand dont make much difference until 70ish+mph.....they do look sweet though! Anyone offer a nose cone for an alpha one that would require minimal mods to smooth out the units housing (ex. minimal fillers / smooth fitting)? I know Bobs offers one but not sure who else may offer....
Not in the 70+ (350ci 60+ish mph) but while painting, thought it would be the time to do one if I were...
04-03-2012, 04:36 PM
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"I think"
On cones
The less drive in the water the better, be it depth and/or length(with a cone)
A cone is needed at higher speeds because of the hole punched into the water in front of the prop. Without a cone at high speed the hole hits the prop and you get blowout, where, punching the hole further forward with a cone allows the water additional time to come back to center and give the prop something to bite. The shape of the cone along with the length help to create a smaller hole for the prop at higher speeds. Lower speeds don't seem to mind so much. Look at your slip numbers. I'll bet they're low.
The length with the cone also adds more stress on the steering because of the leverage created by the added surface area.
On painting
A smooth, painted surface is sticky to the water, and a pain to keep painted.
A sanded lower is less sticky to the water, possibly faster and easy to touch up with 80 grit.
Conclusion
No cone or paint required. If you must spend money, send me $100 and I'll send you some 80grit
On cones
The less drive in the water the better, be it depth and/or length(with a cone)
A cone is needed at higher speeds because of the hole punched into the water in front of the prop. Without a cone at high speed the hole hits the prop and you get blowout, where, punching the hole further forward with a cone allows the water additional time to come back to center and give the prop something to bite. The shape of the cone along with the length help to create a smaller hole for the prop at higher speeds. Lower speeds don't seem to mind so much. Look at your slip numbers. I'll bet they're low.
The length with the cone also adds more stress on the steering because of the leverage created by the added surface area.
On painting
A smooth, painted surface is sticky to the water, and a pain to keep painted.
A sanded lower is less sticky to the water, possibly faster and easy to touch up with 80 grit.
Conclusion
No cone or paint required. If you must spend money, send me $100 and I'll send you some 80grit
04-05-2012, 06:56 AM
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Maiden,
LOL I better get a whole lot of sand paper for $100.00
So better with no paint........ Smooth paint is sticky to water? similar idea ive heard about dont wax the bottom of your boat, it will slow it down......?
I was wanting the lower unit to be aluminum colored....as if it didnt have paint.
There would be more issues with corrosion on the lower unit without paint yes? but then again if its washed well and touched up with sand paper from time to time.
The boat is always garaged so no issues with it sitting in water all the time....guess that would make big diff on corrosion to.
LOL I better get a whole lot of sand paper for $100.00
So better with no paint........ Smooth paint is sticky to water? similar idea ive heard about dont wax the bottom of your boat, it will slow it down......?
I was wanting the lower unit to be aluminum colored....as if it didnt have paint.
There would be more issues with corrosion on the lower unit without paint yes? but then again if its washed well and touched up with sand paper from time to time.
The boat is always garaged so no issues with it sitting in water all the time....guess that would make big diff on corrosion to.
Last edited by jlbspd; 04-05-2012 at 07:00 AM.
04-05-2012, 11:06 AM
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Painted and polished are "sticky".
As far as corrosion, every once in a while I'll pull the boat out and the drive will be stained but never corroded. The staining comes from being in a marina by somebody with a bunch of anodes on their boat. It turns the lower darker. After a few trips out it lightens up, or I could just hit it with that special $100 80 grit.
Myths
Waxing the bottom makes boat faster?
It would create a smooth, sticky surface that would be slower, IF the wax stayed there. Think of the water as wet sand paper. Wax isn't gonna stay long.
A scuffed bottom would be faster. How about putting dimples like a golf ball on the bottom? It speeds the ball up.
Salt is faster than fresh?
Salt is more buoyant so less boat in the water is faster, could be.
Salt is more dense so it should be slower.
I think it's a wash. Any speed gain probably comes from engine performance. Sea level air pressure and temp VS lake level air pressure and temp. Pressure is higher and temps are usually lower on salt.
As far as corrosion, every once in a while I'll pull the boat out and the drive will be stained but never corroded. The staining comes from being in a marina by somebody with a bunch of anodes on their boat. It turns the lower darker. After a few trips out it lightens up, or I could just hit it with that special $100 80 grit.
Myths
Waxing the bottom makes boat faster?
It would create a smooth, sticky surface that would be slower, IF the wax stayed there. Think of the water as wet sand paper. Wax isn't gonna stay long.
A scuffed bottom would be faster. How about putting dimples like a golf ball on the bottom? It speeds the ball up.
Salt is faster than fresh?
Salt is more buoyant so less boat in the water is faster, could be.
Salt is more dense so it should be slower.
I think it's a wash. Any speed gain probably comes from engine performance. Sea level air pressure and temp VS lake level air pressure and temp. Pressure is higher and temps are usually lower on salt.
04-05-2012, 11:42 AM
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Good info.....
So my plans are to go "no paint" on the lower unit. My boat never sits in the water other than when I take it out for the day. As far as anodes....the ones on my drive are pretty eroded away. Will my own anodes cause the unit to darken? or is this more because yours sits in the water over an extended period of time around the other boats.....silly question maybe.. but just clarifying
So my plans are to go "no paint" on the lower unit. My boat never sits in the water other than when I take it out for the day. As far as anodes....the ones on my drive are pretty eroded away. Will my own anodes cause the unit to darken? or is this more because yours sits in the water over an extended period of time around the other boats.....silly question maybe.. but just clarifying
04-05-2012, 12:09 PM
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It's the other boat's anodes. Sometimes it happens, sometimes it doesn't. I'm glad it's just my lower. My neighbor has an aluminum boat that turned dark. He washed it with Scotchbrite.
My anodes are all pitted/ugly but still have plenty of meat so I wire wheel them every year or two.
My anodes are all pitted/ugly but still have plenty of meat so I wire wheel them every year or two.
05-11-2012, 10:03 PM
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"I think"
On cones
The less drive in the water the better, be it depth and/or length(with a cone)
A cone is needed at higher speeds because of the hole punched into the water in front of the prop. Without a cone at high speed the hole hits the prop and you get blowout, where, punching the hole further forward with a cone allows the water additional time to come back to center and give the prop something to bite. The shape of the cone along with the length help to create a smaller hole for the prop at higher speeds. Lower speeds don't seem to mind so much. Look at your slip numbers. I'll bet they're low.
The length with the cone also adds more stress on the steering because of the leverage created by the added surface area.
On painting
A smooth, painted surface is sticky to the water, and a pain to keep painted.
A sanded lower is less sticky to the water, possibly faster and easy to touch up with 80 grit.
Conclusion
No cone or paint required. If you must spend money, send me $100 and I'll send you some 80grit
On cones
The less drive in the water the better, be it depth and/or length(with a cone)
A cone is needed at higher speeds because of the hole punched into the water in front of the prop. Without a cone at high speed the hole hits the prop and you get blowout, where, punching the hole further forward with a cone allows the water additional time to come back to center and give the prop something to bite. The shape of the cone along with the length help to create a smaller hole for the prop at higher speeds. Lower speeds don't seem to mind so much. Look at your slip numbers. I'll bet they're low.
The length with the cone also adds more stress on the steering because of the leverage created by the added surface area.
On painting
A smooth, painted surface is sticky to the water, and a pain to keep painted.
A sanded lower is less sticky to the water, possibly faster and easy to touch up with 80 grit.
Conclusion
No cone or paint required. If you must spend money, send me $100 and I'll send you some 80grit
