Carb Confusion what that??????

[Bill kubiak]

OK, I have a 1997 merc 40 hp 4 cyl 2 stroke and according to all the manuals I have found I am supposed to have a WMA 7 or 9 carb. I have neither.
I have a WMA 1 Carb at least the bottom one that was flooding is
The only engine I can find in the mercury carb index is a 50 HP model that uses a WMA 1 Carb
I heard many times that in the old days guys took the carb off a 15 HP and put it on a 9.9 so they could run in the lakes with HP restrictions and go faster, could that be possible with a bigger engine???

Next I have no idea why this engine even ran, the fuel bowl had water and so much crap and debris in there and how it got in there is a mystery, the fuel had to pass an in line filter and the filter on the motor itself located before the fuel pump.

Fastbullet is correct there is no seat just a rubber tipped needle

I blew air thru the fuel inlet and had junk fly out all over my hand, where did this stiff come from?????

I cannot find the correct float drop for this carb anywhere, does anyone know what it is??

 

[Bill kubiak]

Just double checked and the upper carb is also a WMA 1 carb, Strange,, I am gonna have to pull it off and clean it too

 

[Bill kubiak]

I pulled the top carb off and sure enough the bowl was also full of water and assorted crud, cleaned it out and blew out all the passages with air.
THE Question remains, how did all that stuff get past two filters

 

[yzf125]

I would guess its the remains of good old Ethanol fuel deposits and the inside of your fuel lines coming apart from the Ethanol fuel. May want to replace those fuel lines.

 

[Bill kubiak]

I changed them a year ago guess I will have to do it again
Did some research and found those carbs were used on mid to late 80's Merc 4 cylinder 50 hp motors,. No wonder my 13 ft whaler goes so fast at WOT it scares the hell outa me.

 

[Faztbullet]

It the same motor ..just prop rated..

 

[Bill kubiak]

Please explain what you mean by the same motor just prop rated, the only place I can find that used those WMA 1 carbs was on 1980 something 50 hp motors, mine is a 97 40 hp motor and that thing shoves my 13 ft whaler along at 45 MPH GPS speed which is real scary when you are only a foot above the water. I normally run about 30 mph tops and feel comfortable doing that, but when the bay is real calm I sometimes open er up just to waste gas.

All the kits I see on eBay and elsewhere contain all kinds of assorted gaskets and things but no needle valve and all my carbs require is a Bowl gasket, a mounting gasket, a fiber gasket that goes around the screw on the bottom of the bowl and a new needle valve.
I wrote to Wabro the maker of the carb and asked it they a kit specific for that carb, waiting for an answer.

 

[GA_Boater]

What is your serial number? That's the only way to ID parts needed on Mercs. Of course if a PO has swapped stuff around - Yikes.

 

[Bill kubiak]

Just heard back from WALBRO and they said even tho they made the carb all parts and kits for it are only available thru a mercury dealer. I just called my local Mercury dealer and they want me to bring in the carb so they can match up the parts I need on their Screens, they said I should be able to buy just the few parts I need and they should also be able to give me the float drop measurement once we determine the correct carb. So I will go there tomorrow morning. Nothing is easy.

 

[Bill kubiak]

What is your serial number? That's the only way to ID parts needed on Mercs. Of course if a PO has swapped stuff around - Yikes.

My Serial number is OG554810

 

[Ant-Knee]

If I am correct the only difference in the carbs are the jet sizes,

I had the same issue with a set of carbs I just purchased..
The guy told me it was from a merc V-150 ( Which Is What I Have) So I bought them, Come to find out it was a merc 150, but
a different model, Well the guy didn't tell me that... So after looking them over turns out they are the same carbs but they run different jet sizes...

For instance : My original carbs had jet sizes .034, the carbs I bought had .042 but they are the same carbs..

Just trying to help..

Ant...

 

[Chinewalker]

In the mid 1980s, Mercury (and other brands) re-rated their horsepower from powerhead to propshaft to take into account parasitic losses in the drivetrain. As such, the 50 of the early 1980s became the "Classic 50" which was rated at 45. That eventually morphed into the 40 you have with no real change to the internals. It was more of a marketing ploy, as Mercury had the 50hp triple and needed a gap filler between 30 and 50, hence it was called a 40. There has always been bit of a "fudge factor" in the rating of outboards, as much as 10% on some models, so it all works out in the end. That's why one make's 150 might be "stronger" than another's if they take advantage of that allowed variance...

 

[Bill kubiak]

Ya know as a boy in the early 50's the Merc Super Hurricane 10 ran circles around the Evinrude and Johnson 10's and the Merc 7 hp was just as fast as the other brand's 10's. Everyone always said that mercury de rated all their stuff, but we all knew that Merc was the way to go if you wanted to go fast and we also knew that Evinrude and Johnson never let you down and would always bring you home. I think it was around 1954 or so my Dad bought a Brand new 16 ft family boat called DuCraft Water Bug with the brand new Johnson 25hp electric start motor, can you imagine, an electric start outboard in those days and 25 hp was the biggest motor out there before that I think 18 or 20 hp was the biggest. Now we have 250 and 300 hp outboards.

 

[Bill kubiak]

Just finished swapping out all the engine fuel lines and found a few interesting things, apparently I never changed the almost inaccessible line from the fuel tank plug to the fuel pump, I just changed the lines above the fuel pump running to the filter and the carbs. Anyway they are all new now. The fuel line going to the check valve on the oil pump showed that the oil check value was 1/2 stuck open, I could blow thru it in both directions, I squirted some pb blaster in there followed by some wd 40 and then blasted air thru and all of a sudden I could hear the valve popping open and closed. The lower hard to reach fuel lines were rotting away, I stuck a Q tip in there and it came out pure black with stuff on it.
I am having a lunch break now and then I will clean out the carbs and do as a Merc mechanic at the dealer told me to do, he said it is almost impossible to put a new bowl gasket on there and not have it leak a little. His suggestion was to use a toothpick and put a very thin bead of RTV on that gasket and after it is on and bolted down to rub my finger around the bowl to seal the outside and let it sit and set up overnight, it will not leak, just be a PITA to clean if you ever have to take it apart again.
I am still amazed that the motor ran with all that crud in the bowls and rotting fuel lines and a stuck open oil check valve, these are tough motors

 

[Faztbullet]

Merc mechanic at the dealer told me to do, he said it is almost impossible to put a new bowl gasket on there and not have it leak a little. His suggestion was to use a toothpick and put a very thin bead of RTV on that gasket

I have built a ton of these carbs and never had the bowl gasket leak, sounds like he wayyyy overtightening.Also RTV and fuel are not a good mix as fuel will dissolve it.