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  1. M

    difference between MR and ALPHA1

    I have a MR unit on my boat and was lookin to replace the lower unit with alpha1 the question is does anyone know is the preload pin on it for the upper bearing or the lower bearing on the input shaft right under the water pump. I know the newer alphas have a nut that holds the shaft in place...
  2. M

    Mercruiser "R" drive (lower unit)

    I have a Mercruiser "R" drive (with the preload pin) and the lower unit is broken. Can anyone tell me if the lower units are interchangable with the alpha and what is the function of the preload pin. or can i get a whole set lower-upper unit like alpha one. The "R" drives are hard to find. I do...
  3. M

    Lower unit problem

    Couple weeks ago i hit a rock and destroyed the lower unit. It is a 1984 mercruiser alpha R drive.<br />I got one on ebay but it is a different unit, the housing is the same it is a pre alpha unit the only difference is that my wertical shaft has 13 splines and the replacement one has 8. Can i...
  4. M

    1984 Mercruiser 470

    I have a 1984 Mercruiser 470 170 HP 3.7 inline 4. not sure about the outdrive model at WOT I get around 4900-5000 rpm i have a 19 pitch prop not sure about the diameter. I found a website that has some info about my engine and it says that at WOT the Max RPM should be from 3800 to 4200 rpm i...
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