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Transom water pickup vs through hull

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Transom water pickup vs through hull

Old 04-18-2021, 06:08 PM
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Default Transom water pickup vs through hull

I don't have a fancy racing boat, just a 24 foot bowrider and don't really care about getting top end speed. I have a Mercruiser 6.2L with Bravo 3.

I want to either put in a through hull or a transom water pickup for cooling. I don't like the Bravo 3 system.

My engine access is severely limited. It will be impossible to put the through hull at the back of the boat under the engine unless I pull the motor which I dont want to do.

So I have 2 options:

1. Through hull on the floor of the bilge, on the forward side of the engine
2. Transom water pickup

Here's the hangups that I see with each option:

Forward side through hull -- it's hard to reach this area. I have to lay down on the floor and reach down and I can barely touch the bilge. I think I can install here because I have good visibility, but it's not going to be easy to reach in case of an emergency. The other problem with the forward engine approach is that the way the boat sits in the water. The through hull location would be about 10 feet forward of the transom. When sitting in the water at idle, this area where the through hull will be is about 8-10 inches higher than the aft end near the transom. It's still approx 8-12 inches below the waterline. However I'm concerned that this setup would cause problems when I speed up, as the bow raises into the air and lets air get into the through hull?

Transom water pickup -- I've heard that if you go on plane that the water pressure could be too high and cause hoses to loosen or other issues. My top speed is only 50-55, so I won't be doing a lot of high speed stuff. I have marine rated hose that is supposed to withstand up to 250 PSI and temps of 200 F. Would that kind of hose be good enough to withstand high pressure? Should I put some bends in the tubing so that the pressure that comes off the transom gets reduced by the time it gets to the impeller? If I use the type of intake that just goes straight down into the water instead of the type that curves and aims forward under the boat, would that reduce the pressure? I would like to minimize the use of any equipment between the transom pickup and the impeller if possible, as again my engine access is very difficult. It will be hard to install a lot of extra equipment between the transom and the impeller. Another concern I have about the transom water pickup is that I haven't found one that has a good filter included, it seems they all require you to hook up a separate filter screen. Are there any transom water pickups that include a filter/screen with it already?


Which option would be better? I'm leaning towards the transom water pickup as it will be easier to install and I have a much more direct route for plumbing between the impeller intake and the transom.


Last edited by boater24178; 04-18-2021 at 06:10 PM.
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Old 04-18-2021, 06:58 PM
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...why? MerCruisers number in the millions and all work fine...

I can only assume the boat worked fine new, and works now?
Do you have an issue you're trying to correct?
If not - leave it alone... go for a run and enjoy it...
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Old 04-18-2021, 07:12 PM
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Originally Posted by SabrToothSqrl View Post
...why? MerCruisers number in the millions and all work fine...

I can only assume the boat worked fine new, and works now?
Do you have an issue you're trying to correct?
If not - leave it alone... go for a run and enjoy it...

It's only 2 years old and I had to replace the water inlet on the bravo because it's made out of cheap plastic. Also, it's I think it's a lot harder to check the water inlet line on the Bravo because you have to take off the drive as well as the bell housing every single time. With a through hull or transom water pickup, maintenance is easier and it's a lot easier to get a visual check on water flow than having to dissassemble the drive on the bravo

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Old 04-18-2021, 07:16 PM
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Not a fan of adding holes in the hull.
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Old 04-19-2021, 01:36 AM
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Waste of time and money. You had bad luck with one part once.
If anything, install a water pressure gauge.
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Old 04-19-2021, 07:09 AM
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Originally Posted by Griff View Post
Waste of time and money. You had bad luck with one part once.
If anything, install a water pressure gauge.
Spot on! I have had a few B3’s and never a problem. The high water pressure of an additional pickup can cause other challenges if you do not add a “dump” with a pressure release. Adding additional holes is usually not a good thing. Either of these pickups may slow you down as you are adding drag.
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Old 04-19-2021, 09:20 AM
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Originally Posted by Griff View Post
Waste of time and money. You had bad luck with one part once.
If anything, install a water pressure gauge.
With all due respect, I've already made the decision to do it regardless. I still believe that transom or through hull is superior to the Bravo 3 design.

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Old 04-19-2021, 09:25 AM
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Originally Posted by 36Tango View Post
Spot on! I have had a few B3’s and never a problem. The high water pressure of an additional pickup can cause other challenges if you do not add a “dump” with a pressure release. Adding additional holes is usually not a good thing. Either of these pickups may slow you down as you are adding drag.
I dont have a race boat and don't care about getting an extra few miles per hour speed

High pressure would only occur at rapid speed correct? If I put a loop in the intake line or have a seacock I can partially open it and that should reduce the pressure correct?

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Old 04-19-2021, 09:58 AM
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Originally Posted by boater24178 View Post
I dont have a race boat and don't care about getting an extra few miles per hour speed

High pressure would only occur at rapid speed correct? If I put a loop in the intake line or have a seacock I can partially open it and that should reduce the pressure correct?
How will the seacock know the pressure? Will you mount it on the helm next to a pressure gauge so you can adjust it on the fly?
Nevermind, sounds like you got it all figured out......................................
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Old 04-19-2021, 10:02 AM
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Depending what engine / display setup you have you may ALREADY have access to view water pressure.
( I can see it on my Simrad connected to 525's)

Or install a gauge in one of the block drain ports.

THEN install an adjustable transom mounted pickup.. Adjust the pickup depth to achieve the desired water pressure.


https://www.hardin-marine.com/c-128-water-pick-ups.aspx

Last edited by Boatally Insane; 04-19-2021 at 10:06 AM.
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