Mercury 2.5 water pickup tube

[simpson_3]

I have a 15" mid and need a water pickup tube. Can I just get a 2ft piece from the hardware store and cut it to length? Also, how long is a 3/4 pickup tube for a 15" offshore midsection?

[rjdubiel]

No you cannot. 3/4 copper is not the right size. It is more like 20mm to 20.5mm OD for the 3/4 water tube from merc.

https://www.screamandfly.com/showthread.php?359476-What-is-the-OD-of-a-3-4-inch-water-tube

What I have done to run a 1/2 water tube in a 3/4 water tube adapter plate is to use a standard water pump housing, cut about 1/8" off a 1/2" 15 inch water tube and put the 1/2" water tube grommet inside the 3/4' water tube grommet in the adapter plate. Works just fine.

RJ

[derekfl]

you can't just shorten a tube from a 20 or 25 mid?

[25two.stroke]

you can't just shorten a tube from a 20 or 25 mid?

Only if it is an offshore with a 3/4" tube. Sounds like this guy does not have access to any 3/4" oem water tubes regardless of length.
As I recall the OL of a 15" tube is 13-1/8"

[derekfl]

i guess inshore ones look more like 1/2 inch.

[mach351]

Yeah the 3/4” tube is an animal of it own. Been covered on here a bunch of times. Many have tried to source a replacement to little avail. It is nothing you’re going to find at a hardware store. Most end up just ordering it from Mercury.

[25two.stroke]

@ $212 from mercury I would definitely be looking for alternative options. Good thing I have some spares layin around lol!

[rgsauger]

If we think 20-20.5 mm is right, I can prob find it

[derekfl]

Here is brass. https://www.amazon.com/Pangyoo-PYouo-Metal-Brass-Hardware-Specification/dp/B094F65TXM/ref=mp_s_a_1_4?crid=1NSYZXSHG42O8&keywords=Copper%2BTubes%2B20mm%2B500mm&qid=1683792320&sprefix=copper%2Btubes%2B20mm%2B500mm%2Caps%2C126&sr=8-4&ufe=app_do%3Aamzn1.fos.006c50ae-5d4c-4777-9bc0-4513d670b6bc&th=1&psc=1

[rjdubiel]

https://www.screamandfly.com/showthread.php?359325-Length-of-water-tube-for-F1-midsection-with-shiftable-L-U/page2

here is another thread with some measurements. Like I said in my original post and the link I had, it is like RGSAUGER said, it is 20.5mm OD. 20mm is not very snug in the grommets..

[rjdubiel]

stock 20 inch 1/2 inch water tube length: 18 3/4" (have seen some 18 7/8")
stock 20 inch 3/4 inch water tube length: 18 1/8"
stock 15 inch 3/4 inch water tube length: 13 1/8"

If you choose to use 1/2 inch tube in your 3/4 inch water tube adapter plate, just get a 1/2 inch water tube grommet and put that inside the 3/4 inch water tube grommet in the adapter plate and put the 1/2 inch water tube on, may have to trim 1/16 to 1/8" off it but this way you can run half inch water pump also. I have done it, John Marles also suggested that to me to do if needed and he has posted it here as well.

So to run 1/2 inch water tube in your 3/4 adapter plate with 1/2 inch water pump housing on a 15 inch mid I would think you need the tube to be 13 1/2 inches long or somewhere close to that.

[derekfl]

i would think a little silicone on a 20 mm amazon tube would be preferable to a 1/2 inch tube on a motor that is gonna spend a bunch of time at WOT.

[mach351]

Any motor that deserves to be on a 3/4” one piece hi-po tunerplate probably shouldn’t be risked with Amazon junk and silicone…..I guess that’s just my opinion.

[derekfl]

a 1/2 inch fishin mota tube flows half the water a piece of a piece of 20 mm brass tube that Jeffy Bezos sells. but, a several thousand dollar racing engine? spend the 212 bucks...

[mach351]

That tube may flow twice as much, but let’s not forget both use the same impeller….and both fill the same size block. Now, Merc engineers did it for a reason I’m sure, and I would bet it was for offshore racing with motors coming in and out of the water. I’ve run my 2.4 1/2” one piece plate under everything from xr6 150’s to 300hp ported steel bores….and everything in between. I’ve NEVER had a cooling issue.

back to the original post….this guy already has the 3/4” plate, so it is what it is…..but I’d be buying the right stuff

[rjdubiel]

If you are staying under 8K I would say you are fine with 1/2 inch water tube, but if running hard 8-9K + or so you need to make sure the motor is flowing a lot of volume, that is what the 3/4 tube is for, volume of water supplied to the power head. Especially with the adapter plates with the big ass dump holes in them!

[rjdubiel]

I bought this and it is loose in the grommets, ended up getting a factory 3/4 tube. But my buddy did try to make it work, he had to solder the outside of the tube all the way around and sand it down to get that extra .5-1mm of diameter to make it fit sung in the adapter plate.

https://www.mcmaster.com/products/pipe/material~copper/?s=20+mm+copper+pipe

518847

[derekfl]

That was the general McMaster page. Not the specific pipe that you purchased. But it is probably essentially the same as the 20 mm brass pipe I found on Amazon.