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  1. #1
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    Verado V8 - Blocking off water intake holes

    Center engine on triple yellowfin running low pressure. Apparently it’s quite common to need to block off at least the top 4 holes. Does merc, or anyone else make a plastic or nylon cover or push plugs for this purpose?

    I do not want to tap and screw to plug the holes damaging the paint.


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  2. #2
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    Tap and screw or have a shop weld them closed, smooth out the surface and repaint the lower. Those are your only options. 99% of those who do this do the tap and plug method. Is this a 25” or 30” motor?
    Mark

  3. #3
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    These are what you need. Tap is effortless due to how close the size is. A drop of loctite and you are good to go. I have all but the bottom two blocked off on my 5.44 HD case which has additional pick ups in the nose and it has all kinds of pressure. McMaster Carr has them in stock.

    Joe



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  4. #4
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    Quote Originally Posted by mjw930 View Post
    Tap and screw or have a shop weld them closed, smooth out the surface and repaint the lower. Those are your only options. 99% of those who do this do the tap and plug method. Is this a 25” or 30” motor?

    30” Verado V8 300 , I need to take a look at idle and low speed water pressure too, I believe pressure is low across the board. So the issue could be something else. This was 1st run on Brand new engines.

    im getting 2 different size recommendations, someone else recommended 1/4-20 stainless steel 1/2” long for V8 300?


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    Last edited by OffshoreApparel.com; 01-24-2021 at 05:57 AM.

  5. #5
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    Quote Originally Posted by mjw930 View Post
    Tap and screw or have a shop weld them closed, smooth out the surface and repaint the lower. Those are your only options. 99% of those who do this do the tap and plug method. Is this a 25” or 30” motor?

    30” Verado V8 300 , I need to take a look at idle and low speed water pressure too, I believe pressure is low across the board. So the issue could be something else. This was 1st run on Brand new engines.


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  6. #6
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    Mercury makes a kit to close off holes on a 2.5 and maybe the 3.0 but I've never seen one installed on a Verado and you still have to do some drilling. The tap and plug works well. I had a Verado 300 for a few months and all holes were plugged except the bottom 2. If I was going that route I'd use avaition grade thread sealant. I think it will protect better against the interaction between the dissimilar metals.

    On edit- as I think about this the kit might be for scooping more water in to the sides after plugging a few holes.

    They say the mind is the first thing to go...........
    Attached Thumbnails Attached Thumbnails Click image for larger version. 

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    I've bought and sold 23 boats in 27 years. I fix them up and then get bored and look for another. It's a hobby but I've learned a LOT about boats along the way. And I still don't know chit.

    Running a Pulsare 24 currently.


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  7. #7
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    Wrap duct tape around leading edge back to cover the holes first to see if it makes a difference. On our 450's we plugged all "gill holes" , drilled the nose with 4 additional 1/4" holes and a couple 1/2" holes insides the LU. Went from 8 PSI to 30 PSI.

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    Quote Originally Posted by Mini Max View Post
    Wrap duct tape around leading edge back to cover the holes first to see if it makes a difference. On our 450's we plugged all "gill holes" , drilled the nose with 4 additional 1/4" holes and a couple 1/2" holes insides the LU. Went from 8 PSI to 30 PSI.
    Wow, NICE!

    I did determine this past sunday that pressures are equal to the outer engines when the jack plate is all the way down. If I raise more than 1 inch, that's where the center engine starts to drop, but so does performance. So....I need to play with it a bit more to see if it'll be worth it.


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  9. #9
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    Merc actually released an updated case with more holes in the nose, they also added some holes internally below the water pump. They say it increases water pressure by up to 10PSI. You could drill these holes and probably get the same results.

    Blake

    Merry Christmas & Happy New Year!

    http://injectorservice.com
    Call/Text - 204-326-0390


  10. #10
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    ...those dang floppy-vane impellers i'll tell ya...

  11. #11
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    Sooo. When tapping the holes , do you run the tap/threads all the way? Or must you take care to stop, so the screw sets/stops.

    ‘’Also, what’s the best size set screw and tap size to use in the new V8 hD lowers?

  12. #12
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    You say you lose performance when the water pressure drops? Perhaps you need to lower the center motor so it doesn't break loose before the others.....
    "One of the penalties for refusing to participate in politics is that you end up being governed by your inferiors". Plato .

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