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Thread: WMV-WMH carb info
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11-02-2016, 03:37 PM #1
WMV-WMH carb info
I have been doing a lot of searching and reading here as well as several other forums and websites on the 'net about the WMV-WMH carbs and have noticed a considerable amount of misinformation and misunderstanding. I have spoken with several people that use them with success and even got lucky enough to chat with someone at Mercury. I have what I believe to be a good understanding on them now and thought I would share what I have learned in hopes it may help someone else in the future or at least be a source of reference. If someone comes across this and has more/better knowledge than I do, please let me know if I have some inaccurate information so that I can change it. I am still struggling to locate a source for the idle air vent jet part numbers/sizes and will update this post with that info if/when I get it.
WMV and WMH CARBS
REDUCE IDLE AIR VENT JETS 2 SIZES: Idle air vent jets add more air to the air/fuel mixture, making it leaner. The bigger the jet the LEANER the mixture, smaller the jet is RICHER. Start 2 jet sizes smaller, according to Jay with SST Marine this should put your EGT @ aprox 1050 degrees.
REMOVE THE BACK DRAFT JET - it restricts air flow into the fuel bowl: removing it allows more fuel to flow out of the bowl in response to increased throttle.
MAIN JETS:
If you don't have a EGT you should go up 2 sizes on the main fuel jet, you may lose 100-200 RPM up top but this should be a safe place to start.
If you have an EGT you can go up 1 size and monitor your exhaust temps and then increase jet size as needed to ensure nothing melts. Remember, Lean is mean but fat is where it's at
Here is a chart with Mercury carb jet part numbers and sizes, Vnemous gets credit for sending me this since I couldn't find it when I needed it
Here is a WMV-18 carb view with jets labeled
I'll post more info as I get it.
SlimmHire the handicapped, we're fun to watch
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11-02-2016, 06:57 PM #2
here is what i know after 12 years running rich with wmh 39's
on 245's
off idle 48
idle 72
no back draft
mains 68
16 gallons gas per side 2 hours completely empty
i figured i,m going to redo these so i may as do some jetting
off idle 50
idle 58
back draft 92
mains 68 1/3/4/6 70 2/5
16 gallons gas per side 3 hours running till empty
pistons tops are starting to clean off after couple hours pic 1 piston from each motor , and ran better i still have some tweaking when power heads are done
was thinking go to wmv's but i think stay with wmh but get some 47's off 3.0 liter should be more close jetted for 245's
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11-02-2016, 07:46 PM #3Member
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11-06-2016, 08:01 AM #4
i've never played with the wmv' but have used quite a few wmh's on alot of the builds, basically it is a 3 circuit carb(unlike the old wh series). as said, toss the backdraft jets, progression jets affect your midrange(in the carb throat area), they are air jets, so it is the opposite as stated aboved, increase the size to lean out. mains are in the bowls and are normal(increase size to richen). i haven't had to play with the idle side jetting, as you can adjust the mixture screws and usually wind up where you need to be. these carbs are much more sensitive to jetting changes as compared to the wh series. one thing i will say that i've found, try to start with a set off a 200 or a 245, as the internal drilling/passages are different from different horsepower models, even though the venturi/buterfly size is the same. tried years ago to use a set off a 150, but rejetted them and could never get them to run quite rite. there is a number stamped in the side of the carb mount flange, will begin wmh 21-1,-2,-3. the -1,-2,-3 is placement from top to bottom, and 21 would be the series(what engine it went on). i'll try to get some pics later of the application chart posted. one important note, for example,because someone used a 66 main in a wmh doesn't neccesarily mean it will work in another wmh unless it is the same series number, as the internal passages on some were different.
Last edited by mrcrsr; 11-06-2016 at 08:04 AM.
action mobile marine, 772 528 0754, dealers for aces fuel products,wolf efi, pro marine,latham and gaffrig/livorsi. we build gearcases and modify them(3 litre) to ratchet, and powerheads as well. 21 skater/3 litre wolf efi 113 mph the engine build http://www.screamandfly.com/showthre...-3-litre-build
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11-06-2016, 08:38 AM #5action mobile marine, 772 528 0754, dealers for aces fuel products,wolf efi, pro marine,latham and gaffrig/livorsi. we build gearcases and modify them(3 litre) to ratchet, and powerheads as well. 21 skater/3 litre wolf efi 113 mph the engine build http://www.screamandfly.com/showthre...-3-litre-build
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11-06-2016, 08:46 AM #6action mobile marine, 772 528 0754, dealers for aces fuel products,wolf efi, pro marine,latham and gaffrig/livorsi. we build gearcases and modify them(3 litre) to ratchet, and powerheads as well. 21 skater/3 litre wolf efi 113 mph the engine build http://www.screamandfly.com/showthre...-3-litre-build
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11-06-2016, 09:23 AM #7
Thank you for the input Charlie. I was hoping some more knowledgeable folks would chime in.
I noticed after posting this that WMH carbs are a little different than the WMV. The WMH carbs have 'progression' jets that affect midrange, where the WMV carbs have 'idle air vent jets' that affect idle and off-idle?.
I have wondered quite a bit about that. Dave Strong and I have been chatting about these carbs quite a bit and I just mentioned to him my curiosity about them using the same carb series (ex. WMV-15) for such a wide range of engine displacement. I have thought there had to be something inside that was different.
Thank you, that would be greatly appreciated. Hopefully there can be enough info gathered in one place to help those just starting with these carbs get a better understanding of how they work and how to tune them.
SlimmHire the handicapped, we're fun to watch
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11-06-2016, 09:31 AM #8
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11-06-2016, 09:33 AM #9
Slimm, take a look at the above posted pics from the mercury service manual. Our scanner is not working so I took pics of the pages. U can see the difference in jetting between the various wmh series carbs, even though they share the same venturi size. also the 1990 to roughly 91/92 200's were 7 petal engines as far as the reeds, same with the 245 which would effect the internal passages (how the carbs are made)
action mobile marine, 772 528 0754, dealers for aces fuel products,wolf efi, pro marine,latham and gaffrig/livorsi. we build gearcases and modify them(3 litre) to ratchet, and powerheads as well. 21 skater/3 litre wolf efi 113 mph the engine build http://www.screamandfly.com/showthre...-3-litre-build
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11-06-2016, 09:37 AM #10action mobile marine, 772 528 0754, dealers for aces fuel products,wolf efi, pro marine,latham and gaffrig/livorsi. we build gearcases and modify them(3 litre) to ratchet, and powerheads as well. 21 skater/3 litre wolf efi 113 mph the engine build http://www.screamandfly.com/showthre...-3-litre-build
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11-06-2016, 09:38 AM #11
They also used the wmv on 3 litre mercury, so keep that in mind
action mobile marine, 772 528 0754, dealers for aces fuel products,wolf efi, pro marine,latham and gaffrig/livorsi. we build gearcases and modify them(3 litre) to ratchet, and powerheads as well. 21 skater/3 litre wolf efi 113 mph the engine build http://www.screamandfly.com/showthre...-3-litre-build
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11-06-2016, 09:42 AM #12action mobile marine, 772 528 0754, dealers for aces fuel products,wolf efi, pro marine,latham and gaffrig/livorsi. we build gearcases and modify them(3 litre) to ratchet, and powerheads as well. 21 skater/3 litre wolf efi 113 mph the engine build http://www.screamandfly.com/showthre...-3-litre-build
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11-06-2016, 09:42 AM #13action mobile marine, 772 528 0754, dealers for aces fuel products,wolf efi, pro marine,latham and gaffrig/livorsi. we build gearcases and modify them(3 litre) to ratchet, and powerheads as well. 21 skater/3 litre wolf efi 113 mph the engine build http://www.screamandfly.com/showthre...-3-litre-build
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11-06-2016, 09:47 AM #14
Alot of people use the wh (2.4) carbs on the 2.5. To me, it's the difference between using something designed on a chalkboard vs a computer. The wh are easy to set up (2 circuit carb) whereas the wmh is 3 circuit. It's more complex to set up but the end results are better, engine is more efficient and there is less stuff to go wrong, 2 needles and seats vs 1 per carb. people use what they are comfortable with.
action mobile marine, 772 528 0754, dealers for aces fuel products,wolf efi, pro marine,latham and gaffrig/livorsi. we build gearcases and modify them(3 litre) to ratchet, and powerheads as well. 21 skater/3 litre wolf efi 113 mph the engine build http://www.screamandfly.com/showthre...-3-litre-build
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11-06-2016, 10:06 AM #15
I have a 2002 Mercury Service Manual that shows the same info for the backdraft and off-idle description. I am an old school car hot rod/race car guy so carbs are not something I am scared of which is why I feel so comfortable opening them up and changing things. My boat friends around here are scared to death of anything 'non-factory' and refuse to try or change anything from the way it left the factory. I love tinkering and trying to understand how things work and what was going through the minds of the people that created whatever 'thing' I am intrigued by at the moment, which happens to be these carburetors at the moment hahaha.
Do you think there is enough adjustment in the idle mixture screw to not worry about the idle air jet itself and focus more on the main fuel jet, or will the idle air jet alter mid-range mixture enough to warrant some adjustment?
SlimmHire the handicapped, we're fun to watch
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