I/O (Sterndrive) Conversion to Outboards

Scott Danforth

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Fairing is the correct term for slapping body filler on the fiberglass and making it ssmmmmoooooottthhhhhh
 

tpenfield

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Fairing is the correct term for slapping body filler on the fiberglass and making it ssmmmmoooooottthhhhhh
In search of flatness. . . .

OK, the transom as it is now is not very flat.
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IMG_9363.JPG.
IMG_9362.JPG.
Most likely from lamination overlaps, etc.

I am not sure fairing compound (I have a source for VE fairing compound), is the right thing for the mounting area of the outboard. . . but maybe it is. :unsure:

'Plan B' would be to take a 'flat' piece of something, bigger than the OB mount footprint, and mix up some fiber-strand paste and use the flat piece as a 'surface mold' to give a nice flat area, just where needed.

I think I would need about a 20"x15" piece of flatness based on the engine mount footprint.
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Honda-BF350-Mount-2B.png
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Thoughts? :unsure:
 

Scott Danforth

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Ted, make some PB and use that to fair the surface vs micro-spheres

your fiberglass shop will also have kitty hair or tiger hair
 

tpenfield

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Do they have a measurement for how flat it needs to be like the I/Os?

Do they have a measurement for how flat it needs to be like the I/Os?
I believe the I/O spec is thickness and how 'parallel' the inside & outside surface need to be.

I'm trying to find what outboard motors need, but I would imagine it mainly applies to the outside surface.
 

Scott Danforth

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I believe its supposed to be flat within 1.5mm over a 1 meter length (with a straight-edge). but that is memory.

then I recall a 3mm parallel requirement (which doesnt make sense for parallel)

I would want the transom flat where the motor clamp sits on the outside from a loading standpoint.
 

tpenfield

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OK, my fiberglass estimates have been way low and I am heading out to grab another pail of resin and another roll of 1708 should arrive today.

I took a look at what I've used and it is adding up (resin vs. cloth), but it seems that making things thick really uses up the materials, since each layer of fiberglass yields about 1/20th of an inch in thickness.

Here are my numbers of material usage . . .
Screenshot 2026-03-24 at 6.46.45 AM.png
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I figured based on the cloth usage, how much resin I should have used.

So, 30 gallons used and I can account for just about all of it (figuring fillets was probably a gallon) . . . so 29+1=30 ! :unsure:

I just hope the end of material buying is near . . . :rolleyes:
 

Pmt133

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Wish you were closer. You could have the rest of my CSM and 1708. It's odd, I can't really give the stuff away it seems.
 

FLATHEAD

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Had some time yesterday to catch up on this thread. Outstanding work. Looking forward to when you attach it.
 
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