# Lower unit pressure tester



## sureshot006 (Sep 8, 2010)

Anybody make one? I see a couple options just surfing the web but was interested in other potential options.

Lower unit looked a lot more tan/brown than I've ever seen in years past...


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## sureshot006 (Sep 8, 2010)




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## CrawlerHarness (Dec 9, 2017)

Following. that is a new one for me.


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## Offfishn (Nov 12, 2017)

Looks like Lake Erie water !


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## sureshot006 (Sep 8, 2010)

CrawlerHarness said:


> Following. that is a new one for me.


Basically just trying to find where a leak might be by putting a few psi of air to it. Hoping its something silly like a bad vent screw gasket but could be worse. Motor is 21 yrs old so...


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## bobsbeads (Jan 19, 2014)

sureshot006 said:


> Basically just trying to find where a leak might be by putting a few psi of air to it. Hoping its something silly like a bad vent screw gasket but could be worse. Motor is 21 yrs old so...


There are several different seals that could be leaking. I have a 1982 Johnson 25 hp. Tried several fixes , didn’t work. Now I just change the oil every fall .


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## MisterTom (Sep 13, 2018)

Thinking about making one as well this winter. Planned to cut the end off an old gear oil pump - plastic screw with clear hose - and jury rig it to a quick disconnect for the air compressor. Only needs to hold a few psi.

Three places for seals - prop/gear/drive shafts. Plus the 2 filler plug washers, sometimes the fiber ones need to be scraped off if they get mashed in. Fixing the seals and gearcase stuff on smaller motors is pretty easy, though there are some helpful “tricks” to know. Haven’t dug into the bigger HP with shims, but I’m gonna have to soon.


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## sureshot006 (Sep 8, 2010)

bobsbeads said:


> There are several different seals that could be leaking. I have a 1982 Johnson 25 hp. Tried several fixes , didn’t work. Now I just change the oil every fall .


I change every fall. That's how I found it. Usually a tiny amount of white but this time was very different. I don’t want to open it up next fall to find half water.


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## Broadbill (Jan 3, 2016)

Just reseal the whole gearcase, seals are cheap. most likely from fishing line on the prop shaft. Removing your propeller a couple time a year to check for fishing line behind the thrust hub is an easy measure of prevention. Don't forget, the seals on the fill and vent plug should be replaced every time you change the lube.
If you pressure test it, no more than 12 psi. I have seen guys blow out seals using to much pressure.


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## sureshot006 (Sep 8, 2010)

Broadbill said:


> Just reseal the whole gearcase, seals are cheap. most likely from fishing line on the prop shaft. Removing your propeller a couple time a year to check for fishing line behind the thrust hub is an easy measure of prevention. Don't forget, the seals on the fill and vent plug should be replaced every time you change the lube.
> If you pressure test it, no more than 12 psi. I have seen guys blow out seals using to much pressure.


Easy to replace plug gaskets, shifter And under water pump but isn't the prop shaft seal a PITA requiring special tools?

This could just be plug seal wasn't 100%. Hoping pressure test to around 10 psi will help me find it.


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## Broadbill (Jan 3, 2016)

Not always are special tools needed, i have changed a few with a standard seal puller made by Craftsman and some picks to pull the seal off the shaft, care must be taken. you don't want to score the shaft.


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## sureshot006 (Sep 8, 2010)

Broadbill said:


> Not always are special tools needed, i have changed a few with a standard seal puller made by Craftsman and some picks to pull the seal off the shaft, care must be taken. you don't want to score the shaft.


Most people have hammers, screwdrivers and wrenches. I dont have a puller of any sort. But I have an acquaintance who is an airplane mechanic so he probably does.


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## BumpRacerX (Dec 31, 2009)

No one around you with the right tool setup? 

Theoretically...you could probably put the top/vent plug in the drive and then put an old gear oil pump nozzle on an empty bottle and pump. Soapy water on the seals once it's pressurized. Even a bike pump would work if you could get a good enough seal.


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## sureshot006 (Sep 8, 2010)

BumpRacerX said:


> No one around you with the right tool setup?
> 
> Theoretically...you could probably put the top/vent plug in the drive and then put an old gear oil pump nozzle on an empty bottle and pump. Soapy water on the seals once it's pressurized. Even a bike pump would work if you could get a good enough seal.


I talked to a guy this afternoon that has enough crap to make something work. Just not exactly ideal. We talked about a regulated air supply to 10 psig and saying screw the "does it hold" test and just use soapy water as detection. I have a filler pump and the screw fitting for it so i think i will get good enough seal to push air out of any leak point. He's got a puller that's probably long enough, too. Probably all set.

One thing I need to do though is flush some clean oil through to get as much of the brown crap out as possible. Plain ol cheap motor oil okay for that?


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## bobberbill (Apr 5, 2011)

What brand of gear oil was drained? Differences between OEM, synthetics, and standard 80-90 weight. I use Valvoline in my engines with good results. A little water homogenizes and usually will turn the oil milky, unless it's set for a while and separated. Very possible everything's OK. Make sure it's drained before freeze.


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## sureshot006 (Sep 8, 2010)

bobberbill said:


> What brand of gear oil was drained? Differences between OEM, synthetics, and standard 80-90 weight. I use Valvoline in my engines with good results. A little water homogenizes and usually will turn the oil milky, unless it's set for a while and separated. Very possible everything's OK. Make sure it's drained before freeze.


Quicksilver marine gear oil. I've seen a small amount of milky oil before but this is far more than I've seen in 9 years of annual changes. I will say "most" of the oil coming out was still very dark. Not greenish anymore but relatively clean. 

It has been draining probably a total of 8 hours now. Its in an unheated garage so a little slower than normal draining.


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## FREEPOP (Apr 11, 2002)

Put the oil in a milk jug or something clear, let set and see if there's separation.

Pressurizing the internal case will most likely not be best because in application, the pressure is external.


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## ice house (Dec 27, 2017)

its water, turns oil to choc shake.


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## bobberbill (Apr 5, 2011)

Take the top vent screw out and find a piece of small hose and blow air - or compressor - and it'll drain the remainder out. Could be a little messy. Should only have about a quart +- a little. At least make sure the top vent screw is open. Laughed at my neighbor and it tricked me once. He had a top drain for the lower unit and a flush plug that looked the same and were side by side on his Yamaha. Had the flush screw out and couldn't figure why it wasn't draining.


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## FREEPOP (Apr 11, 2002)

The presence of a little water could be from condensation.


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## sureshot006 (Sep 8, 2010)

FREEPOP said:


> Put the oil in a milk jug or something clear, let set and see if there's separation.
> 
> Pressurizing the internal case will most likely not be best because in application, the pressure is external.


Yeah I just figure it is easier to check. If i see something it will be obvious. If I don't, I still know there is a leak and will have to try the ol shaving cream trick.


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## sureshot006 (Sep 8, 2010)

FREEPOP said:


> The presence of a little water could be from condensation.


From last winter when I sealed it up?

Its never been this bad in 9 years. Not even close.


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## FREEPOP (Apr 11, 2002)

sureshot006 said:


> From last winter when I sealed it up?
> 
> Its never been this bad in 9 years. Not even close.


Was it warm and humid when you last sealed it?

They use this for gas tanks to check for water.

http://cspforestry.com/products/kol...UidtQhNJeVCDB7rYSeEc27kdvHh1zQbRoCaMAQAvD_BwE


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## sureshot006 (Sep 8, 2010)

This is the first little bit. I put the plug back in to get the camera but that's what it looked like initially.


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## sureshot006 (Sep 8, 2010)

FREEPOP said:


> Was it warm and humid when you last sealed it?
> 
> They use this for gas tanks to check for water.
> 
> http://cspforestry.com/products/kol...UidtQhNJeVCDB7rYSeEc27kdvHh1zQbRoCaMAQAvD_BwE


Not that I remember. I think it was December last year. Doesn't mean it wasn't humid I guess.


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## BumpRacerX (Dec 31, 2009)

You have a seal bad. End of discussion. If you're lucky it's just the washer/o-ring on the plugs. If you're not...it's an actual seal.


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## BumpRacerX (Dec 31, 2009)

IDK what would happen if you used motor oil to try to get the last of the moisture out. I'd probably leave it open and let it air out for a few days. Quicksilver is like $10. Just buy two quarts and fill/drain it to flush would be what I'd do. You also likely won't use an entire container for the actual final fill...so you might be able to get away with one.

Pressure test it to find the bad seal (soapy water on the seals when pressurized) and address. 

Lower unit seals go bad. Just part of owning a boat. 

Did you bump anything this year? How's the prop look?


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## Lund Explorer (Jan 23, 2011)

BumpRacerX said:


> You have a seal bad. End of discussion. If you're lucky it's just the washer/o-ring on the plugs. If you're not...it's an actual seal.




But let's be clear, its 2020.


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## fowl (Feb 15, 2003)

Water in there is bad. Much cheaper to be proactive and replace seals, etc compared to rebuilding a destroyed lower unit. Smart to nip it in the bud. 


Sent from my iPhone using Michigan Sportsman


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## BumpRacerX (Dec 31, 2009)

Question...do you put new drain/top plug screw seal/washers on each time? Reusing most of the new ones is a no-no. 

Also...make sure you only have one on there. "A friend" drained and refilled his lower unit. Put on a new one...and forgot to take the old one out of the hole. 

Ooops.


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## BumpRacerX (Dec 31, 2009)

fowl said:


> Water in there is bad. Much cheaper to be proactive and replace seals, etc compared to rebuilding a destroyed lower unit. Smart to nip it in the bud.
> 
> 
> Sent from my iPhone using Michigan Sportsman


This. My dad and I clashed on this. 

It's just a little water son it'll be fine. I just change it every year.

First time out he destroyed his lower unit this year lol.

I've also seen them have so much water in them that they freeze and crack the lower units during the winter. 

(spent a couple years as a special lines/marine adjuster)


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## anagranite (Oct 23, 2010)

I vote for a bad seal, check for line first. I have a bad one on one of my Suzukis but I just pulled the boat out of the slip and changed the oil 4 times this year because everyone was backed up and wanted the lower until for 2-4 weeks. 

Here's a video I'm sure you found already but this guy is pretty cool.


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## sureshot006 (Sep 8, 2010)

BumpRacerX said:


> IDK what would happen if you used motor oil to try to get the last of the moisture out. I'd probably leave it open and let it air out for a few days. Quicksilver is like $10. Just buy two quarts and fill/drain it to flush would be what I'd do. You also likely won't use an entire container for the actual final fill...so you might be able to get away with one.
> 
> Pressure test it to find the bad seal (soapy water on the seals when pressurized) and address.
> 
> ...


Prop isn't perfect but no real vibration that I can tell. Don't recall hitting anything this year. Could be line behind the prop though.

Motor is a 1999 so yeah its probably time.


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## sureshot006 (Sep 8, 2010)

BumpRacerX said:


> Question...do you put new drain/top plug screw seal/washers on each time? Reusing most of the new ones is a no-no.
> 
> Also...make sure you only have one on there. "A friend" drained and refilled his lower unit. Put on a new one...and forgot to take the old one out of the hole.
> 
> Ooops.


Yeah I did last year (I think...). Of course if I didn't, I wouldn't remember anyway lol. Looked like only 1 when I pulled plugs but I will pick at it later to see if one is embedded in there.


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## sureshot006 (Sep 8, 2010)

anagranite said:


> I vote for a bad seal, check for line first. I have a bad one on one of my Suzukis but I just pulled the boat out of the slip and changed the oil 4 times this year because everyone was backed up and wanted the lower until for 2-4 weeks.
> 
> Here's a video I'm sure you found already but this guy is pretty cool.


If I can't find it with a "rigged" method I was gonna buy a setup similar to that.


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## sureshot006 (Sep 8, 2010)

BumpRacerX said:


> This. My dad and I clashed on this.
> 
> It's just a little water son it'll be fine. I just change it every year.
> 
> ...


I already prepped my wife. Thats part of why I took pics LOL. I told her if the lower is bad I may as well buy a new boat


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## Ranger Ray (Mar 2, 2003)

Problem solved.


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## sureshot006 (Sep 8, 2010)

Hey... now I know what to do with one of the 5 vacuums my wife has! Vac check solved.


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## sureshot006 (Sep 8, 2010)

fowl said:


> Water in there is bad. Much cheaper to be proactive and replace seals, etc compared to rebuilding a destroyed lower unit. Smart to nip it in the bud.
> 
> 
> Sent from my iPhone using Michigan Sportsman


You suggesting while I am working on it I should just replace all seals regardless of leaking or not?


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## FREEPOP (Apr 11, 2002)

sureshot006 said:


> You suggesting while I am working on it I should just replace all seals regardless of leaking or not?


At that age I would change all seals. Best insurance against big problems.

Fwiw, we made trim and tilt units for Mercury Marine in the 80s and 90s.


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## Schroeder's Song (May 25, 2004)

I need to hit the hardware store for a fitting & hose to plumb this onto my cooling system pressure tester, but I have just what you are looking for.
If you would like to borrow it, pm me your contact/cell info and we can arrange a meet up.
I am in westland so maybe south of the airport somewhere would be halfway???
Let me know...


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## kroppe (May 7, 2000)

sureshot006 said:


> Why new lower unit? If I have to put $2300 into it I'd rather just buy a new (used) boat. Its a good excuse anyway...


The new unit breathes some life into the motor. I’m a throw-parts-at-it kind of guy, so that’s how I address things like this. Yes it’s a bit more money to do it this way. What is your expected holding period for this boat? You mentioned a new-to-you boat a couple of times.


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## sureshot006 (Sep 8, 2010)

I should mention there was a normal amount of fine metal "fuzz" on the drain plug magnet. No chunks of any kind.


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## Shoeman (Aug 26, 2000)

Unless the housing's shot a few seals will stop the intrusion


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## sureshot006 (Sep 8, 2010)

kroppe said:


> The new unit breathes some life into the motor. I’m a throw-parts-at-it kind of guy, so that’s how I address things like this. Yes it’s a bit more money to do it this way. What is your expected holding period for this boat? You mentioned a new-to-you boat a couple of times.


I've been very conservative with finances. Maybe too conservative. I could easily afford a new lower but would rather upgrade from a 20+ year old 2 stroke. I just don’t have the leverage with my wife right now. She says she wants a lake house if I buy a boat lol. We don't see eye to eye when it comes to a 2nd property (id rather rent by the week and buy hunting land, which she says is not useful to her) or the "need" for a new boat. "Before you buy a boat we should do xyz...". Then I admit, I don't NEED a shiny new boat to catch fish... but then again, what am I to do with what I've accumulated?

Now I'm getting into the weeds and too personal lol. Bottom line is I don't see the need for a new lower unless there are real signs of damage. A little water has potential to cause damage but it "appears" I caught it in time. No abnormal metal shavings or chunks. No noises I'm aware of.


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## FREEPOP (Apr 11, 2002)

sureshot006 said:


> I should mention there was a normal amount of fine metal "fuzz" on the drain plug magnet. No chunks of any kind.


At 20 years it should have at least that.


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## sureshot006 (Sep 8, 2010)

Shoeman said:


> Unless the housing's shot a few seals will stop the intrusion


Ya. I don't see any damage but its backed into the corner of the garage where I have little room to work. Hasn't been a priority to work on yet. I'm sure I will get to it the week before the walleye run


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## sureshot006 (Sep 8, 2010)

FREEPOP said:


> At 20 years it should have at least that.


Honestly I don't think it had all that much wear on it when I bought it in 2011. The damn thing looked mint. I have used and abused it.


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## perchjerker (Feb 8, 2002)

Schroeder's Song said:


> View attachment 615113
> I need to hit the hardware store for a fitting & hose to plumb this onto my cooling system pressure tester, but I have just what you are looking for.
> If you would like to borrow it, pm me your contact/cell info and we can arrange a meet up.
> I am in westland so maybe south of the airport somewhere would be halfway???
> Let me know...


I have a cooling system pressure tester (was a mechanic for 20 years) so thats what I use as well. I would NOT use compressed air to test this. too easy to blow a seal and cause more problems

and no way I would put a new lower unit for a problem like that! I have a 1995 Johnson 200 its been perfect all these years, a little seal leak is expected and easy to repair


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## sureshot006 (Sep 8, 2010)

Schroeder's Song said:


> View attachment 615113
> I need to hit the hardware store for a fitting & hose to plumb this onto my cooling system pressure tester, but I have just what you are looking for.
> If you would like to borrow it, pm me your contact/cell info and we can arrange a meet up.
> I am in westland so maybe south of the airport somewhere would be halfway???
> Let me know...


I appreciate the offer and if needed I will contact you. Looks like an ideal rig. Is that plug plastic? Hard to tell in the picture. I do have a fitting for fill pump that threads into the fill hole and of course the tubing. Thats how I planned to test it with a regulated air supply.


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## sureshot006 (Sep 8, 2010)

perchjerker said:


> I have a cooling system pressure tester (was a mechanic for 20 years) so thats what I use as well. I would NOT use compressed air to test this. too easy to blow a seal and cause more problems


I can see that... you wouldn't use a high quality regulator like for a good airbrush?


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## perchjerker (Feb 8, 2002)

I am not a painter I am a mechanic.


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## sureshot006 (Sep 8, 2010)

perchjerker said:


> I am not a painter I am a mechanic.


Ha yeah I understand. Just something I have available.


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## perchjerker (Feb 8, 2002)

I am sure it would be fine I just prefer pressurizing by hand

and I would try to find out what the spec is, 10 psi might be too much I really have no idea on that


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## Schroeder's Song (May 25, 2004)

[QUOTE="sureshot006, post: 8811841, member: 51542". Looks like an ideal rig. Is that plug plastic? Hard to tell in the picture. 

That is a metal plug ( an old one the slot had gotten sloppy) with a hole drilled thru, silver soldered to a 1/4" brass barb. I notched the barb fitting to fit in the slot so it can be torqued for a good seal.
I had been wanting to make one for years and your post motivated me lol.
I am going to put it together on an old cooling system pressure tester. Pump by hand with an guage to monitor pressure loss. Should work great, and now that I have it, I hope to never need it lol!

I also have the plastic fill fitting but doubt that will seal well for monitoring pressure drop.

When you get ready to start working on your boat, your welcome to use it.


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## sureshot006 (Sep 8, 2010)

perchjerker said:


> I am sure it would be fine I just prefer pressurizing by hand
> 
> and I would try to find out what the spec is, 10 psi might be too much I really have no idea on that


I think its something like up to 15 but I have to get my manual out.


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## Schroeder's Song (May 25, 2004)

Forgot to add I also have a mighty-vac to perform a vacuum test as well.


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## piketroller (Oct 24, 2016)

sureshot006 said:


> I think its something like up to 15 but I have to get my manual out.


You should be able to detect a leak at 2-4 psi. At 10 psi I’d start getting concerned about damaging a good seal and getting a false diagnosis. These things are not pressure vessels. At 10 psi, that’s 160 pounds pressing on every surface inside the casting as big as a dollar bill.


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## perchjerker (Feb 8, 2002)

agreed


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## sureshot006 (Sep 8, 2010)

piketroller said:


> You should be able to detect a leak at 2-4 psi. At 10 psi I’d start getting concerned about damaging a good seal and getting a false diagnosis. These things are not pressure vessels. At 10 psi, that’s 160 pounds pressing on every surface inside the casting as big as a dollar bill.


Likely true. videos showing how to test are recommending 10-12 psig.


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