Mercury Carb Questions

[DamianJP]

First off here are the pics that go along with this.

http://s281.photobucket.com/albums/kk233/damianjp_photos/Mercury 1989 XR4 150HP/

I bought this rig with Top WH41 and MID / BOT WH27 it seems. At the start idle was ruff and top end okay. So I changed the idle jets because the 27's were off. And bam smooth as silk idle. I started to investigate my Main jets but broke 1 and quit after it was 20+$. I snagged a set of WH41's from ebay and so far the idle jets are all .052 .Then I had to dig in again and busted 2 more.

Lemme try and form this up

1)Whats the best method/tool to remove main jet plugs
2)Are bowls from my new/old set interchangable
3)Are floats (1 composite / 1 plastic) from old/new set interchangable
4)What should my jet's be on the 41's /it is Stock/
5)Do I really need to change the needle seat? If so whats the best method/tool to use?


Thanks,
Damian

 

[j_martin]

Re: Mercury Carb Questions

First, I've never had that kind of trouble with the brass parts. Tools need to fit well, and be in good shape. Brass isn't as strong as steel, so an ill fitting tool will put forces on the part that will break it. A poorly shaped screwdriver, for instance, will shred a jet or seat.

To answer your questions. The hard plastic floats replace the foam floats. They are NLA at merc, and the aftermarket folks never made them, so the source is junk carbs. The foam floats tend to sink in modern fuel.

The needle and seats need to be removed for cleaning, but if in good shape can be reinstalled with new gaskets. The gasket needed is in the relatively innexpensive gasket kit.

WH41's are the correct carb for your XR4. I don't have the jetting chart handy, but if someone else doesn't chime in, I'll get it Monday. Stock jetting on the XR4 is good to go, slightly rich but very responsive to throttle. I think the only difference between the 41 and 41A is the idle jet. the A jetting works better.

If the bowls look the same, they will interchange. Watch out for distortion caused by poor torqing practice, and always use new gaskets, especially the little one in the center of the bowl.

Even though the WH carbs all look alike, there are major differences in the body itself and the porting. All the common stuff, like floats, needles, gaskets, and probably bowls interchange.

One note. The jetting goes with the carbs, not with the application. In other words the same carbs on different engines use the same jets, (at least they're close) Different carbs on the same engine might use widely different jets for the same mixture.


hope it helps
John

 

[j_martin]

Re: Mercury Carb Questions

I found it.

WH41
Main .074
Idle .052
Vent .076

WH41A
Main .074
Idle .048
Vent .076

The only difference is the A set runs idle slightly leaner.

On mains, larger is richer
On Idles, Larger is leaner
On vents, Larger is rich sooner.

hope it helps
John

 

[DamianJP]

Re: Mercury Carb Questions

Once again John... Thank You !

I know something we talked about but some not.Hate to drive ya nuts , but I like to learn.(hard way sometimes)

1) I used an open end wrench , so Ill try the screw driver mabey it will turn the whole plug and not snap the head (breaks were the mixing holes are).

2) On the seat I'm leary of more brass , what tool do you use?
(Tight fitting big flathead?)

3) My old carbs had no vent jets in the front of it. New 41's came with .076 what should I do. I live in south FL.

Also gonna peak into the 41's to check Main jets. Checked the idle's they are all 0.52 but will pick up a "A" jet set too.All the idles and vent jets are all good so far on 41's , just gotta check mains.

Ill post updates/results


Thanks again John,
Damian

 

[j_martin]

Re: Mercury Carb Questions

Once again John... Thank You !

I know something we talked about but some not.Hate to drive ya nuts , but I like to learn.(hard way sometimes)

1) I used an open end wrench , so Ill try the screw driver mabey it will turn the whole plug and not snap the head (breaks were the mixing holes are).

2) On the seat I'm leary of more brass , what tool do you use?
(Tight fitting big flathead?)

3) My old carbs had no vent jets in the front of it. New 41's came with .076 what should I do. I live in south FL.

Also gonna peak into the 41's to check Main jets. Checked the idle's they are all 0.52 but will pick up a "A" jet set too.All the idles and vent jets are all good so far on 41's , just gotta check mains.

Ill post updates/results


Thanks again John,
Damian

1. I use a 6 point 1/4 drive socket.

2. Flathead blade that just barely clears the bore so it is the full width of the seat, hollow ground so the end is square, not tapered.

3. Jetting is a function of the carb. You need the vent jets.

Don't worry about the idle jets now. Get it running. I screwed up a bit. .048 in the idle is fatter than .052". Put em in if it stumbles when you punch outa the hole. Otherwise leave em lean.

hope it helps
John

 

[thefairlaneman]

Re: Mercury Carb Questions

I had a jet seat stuck also. I soaked it with PB blaster and used a tight fitting socket like the prior post said and secured the carb in a vise. Came out easy then.

 

[DamianJP]

Re: Mercury Carb Questions

Got the 41's done , and posted more pics.

http://s281.photobucket.com/albums/kk233/damianjp_photos/Mercury 1989 XR4 150HP/

John// Thanks for the tips on the brass stuff aswell as everything again.At 25$ each those main's suck when they break. Also I grabbed 2 of those Bridge Rectifiers , is the hook up pretty much the same?

thefairlaneman// What is PB Blaster? And you used PB and socket to loosen what main plug or needle seat? Thanks for the help these brass pieces drive me nuts.

Main .074
Idle .052
Vent .076
All new gaskets and stuff
Carbs came from Lousiana looked like it was on a salty XR4.
So I used my old mixing chamber plates and screws for plate and bowls , as they were weathered.

Everything is in and I can't wait for tommarrow. I just gotta slow down when I get to the boat and take it slow.

Once again THANK YOU!
Damian

 

[j_martin]

Re: Mercury Carb Questions

Got the 41's done , and posted more pics.

http://s281.photobucket.com/albums/kk233/damianjp_photos/Mercury 1989 XR4 150HP/

John// Thanks for the tips on the brass stuff aswell as everything again.At 25$ each those main's suck when they break. Also I grabbed 2 of those Bridge Rectifiers , is the hook up pretty much the same?

thefairlaneman// What is PB Blaster? And you used PB and socket to loosen what main plug or needle seat? Thanks for the help these brass pieces drive me nuts.

Main .074
Idle .052
Vent .076
All new gaskets and stuff
Carbs came from Lousiana looked like it was on a salty XR4.
So I used my old mixing chamber plates and screws for plate and bowls , as they were weathered.

Everything is in and I can't wait for tommarrow. I just gotta slow down when I get to the boat and take it slow.

Once again THANK YOU!
Damian

The stator yellows go to the AC or sine wave (~) terminals. + goes to battery, and - needs a 14 G wire to ground.

I solder loops of 14 G wire to the rectifier terminals, making an eye to which the ring tongue terminals on the wires can be bolted with stainless machine screws and nuts. You can just cut and solder, or (last choice) put blade terminals on the wires. Blade connectors tend to fail in time.

Once on the motor, you will never have to replace it again.

Hope it helps
John

 

[j_martin]

Re: Mercury Carb Questions

PB-Blaster, WD-40, Deep-Creep. All are penetrating lubricants.

 

[thefairlaneman]

Re: Mercury Carb Questions

Part of the answers did mention removal of the needle and seats. I wanted to offer a sujestion to help with this if it were a problem .(post #2)

 

[DamianJP]

Re: Mercury Carb Questions

Thanks fairlaneman everybit helps


Damian

 

[marquise]

Re: Mercury Carb Questions

Hello I have a 1995 150 Mercruiser and i don't know whats going on here,one time i could see gas leaking from carb when i would prime it,let it sit prime it again don't see gas leaking from carb,i changed fuel filter i could see small deposits in other one, now what i don't want in wich this has happen to me ,is to get back out and start fishing stop 4 or 5 times and then to crank the engine up to leave on that last time and it will not start,it has to actually sit,because when i get home and run it through the hose it starts right back up,i am getting frustrated what can i do, if needed to have carbs rebuilt what is a estimated cost , i live in powder springs georgia,