Originally Posted by low_psi

I don't know about the "turbulance" factor, but I do know from experience polished air cooled V-Twin Motors do run hotter than non-polished aluminum motors. This is due to the reduced surface area of the castings. And on the other side the V-Twin motors that have been "diamond cut" run cooler becasue each cut adds surface area. This effect is amplified on motorcycle motors becasue they are air cooled, so would smoothing and polishing aluminum heads on a watercooled motor make that much of a difference? I doubt it would make any more difference than if they were painted..... Personally I wouldn't do it, sanding and polishing aluminum is a pain in the butt, not to mention a pain to keep looking nice. Assuming they are cast aluminum heads, cast aluminum is very pourous, so they will show water spots very easy and will require a lot of work to remove spots and stains. I don't know where you boat, but if saltwater, the salty air itself will dull the polished surface quicker, making more work for you to make shiny again. Just sounds like a lot of work for something that doesn't make the boat faster or louder.......

If you do decide to sand and polish your aluminum heads (or any aluminum) make sure to wear (at minimum) a dust mask. I would suggest a filtered respirator. Especially if you will be using high speed tooling. Aluminum dust has proven to casue very nasty side effects which include, but not limited to, Alzheimer's, and numerous respitory conditions.