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  1. #1
    Gold Member Gold Member ziemer's Avatar
    My Boats:
    1995 Allison Grand Sport & 1990 30' Velocity
    Join Date
    Apr 2006
    Location
    St. Cloud, FL
    Posts
    1,151

    Imco Thumper - Opinions???

    So I've got a set of 502 EFI's that are completely stock, and I currently plan to keep them that way.

    Well, the last time out, I noticed a little more steam out of the starboard motor than the other so I decided to pull the risers/manifolds apart. My suspicions were correct as the mating surface on one of the risers was rusted pretty bad, and won't provide a good seal even with a new gasket.

    The port side looks good, and cleaned up fairly well, so they are re-usable.

    Now, the question...I found a set of used Imco Thumper manifiolds and risers for what seems like a good price, and these are cast aluminum, so I should have quite the issues as I do with the cast iron.

    I do boat in the salt, however, now that I own the boat it will be flushed after every salt use.

    Should I replace everything with the used Imco's? Buy new risers for the stock? I can get a set of stainless risers for the stock manifolds... Keep the stock arrangement and save for a better aftermarket option????

    Again, these motors will stay stock for years to come...

    Thanks!
    1995 Allison Grand Sport
    1998 Mercury Stock 2.5-260 SS

    1990 Velocity 30' - 502 MPI's

  2. #2
    Platinum Member Platinum Member coopsmirage's Avatar
    My Boats:
    2004 Formula 292
    Join Date
    Aug 2010
    Location
    MCHENRY IL
    Posts
    415
    I have a perfect set of stainless merc risers if you are interested? Fresh water use....250.00 shipped

  3. #3
    Platinum Member Platinum Member Expensive Date's Avatar
    My Boats:
    05 35 Fountain EX
    Join Date
    May 2006
    Location
    West Creek NJ
    Posts
    4,117
    I have them on my 6.2s for two years in salt. No problems so far,and the are much lighter than cast iron. The boat will ride better, at least mine did.

  4. #4
    Registered
    My Boats:
    42' Sundancer from 2004 formerly known as Big azz cruiser from 2004. Still looking for the right new 38-42 ft. v-bottom!
    Join Date
    Apr 2009
    Location
    Denmark and hopefully some place nice
    Posts
    1,852
    Quote Originally Posted by Expensive Date View Post
    I have them on my 6.2s for two years in salt. No problems so far,and the are much lighter than cast iron. The boat will ride better, at least mine did.
    +1

    They won't net you much power, if any. But the weight savings are noticable. Thumpers are not the prettiest of manifolds, but hey, that's subjective. They do however look better than the merc stuff. If you flush as you should, no problem.


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