Carbs

[Glastron1987]

What are the physical and performance differences among the WH, WMH, and WMV carbs? Does newer style mean they are better?

[Glastron1987]

So far what I've been able to find is that:

1) the WH (oldest) have 2 bowls each
2) the next ones (WMH) have 1 bowl each and the earlier versions of these have an accelerator pump
3) and the newest (WMV) have 1 bowl each with no accelerator pump

Not sure why the pump is needed or not, but seems the newest models (WMV and some WMH) would be the simplest and therefore less prone to failure or trouble; but that is only a guess.

[mach351]

Wh are the simplest. They are tunable on only two circuits as where the later carbs are tunable on three (a middle circuit if you will). Wh's are easiest to tune, but you can get a whm tuned closer, just takes more knowledge. Accelerator pump versions are junk...no performance advantage and increased fuel consumption, plus some of the parts are NLA. Haven't messed with the WMV's much, but I'm sure they're decent.

[Keithm18]

Hi Guys. Not intending to hi-jack the thread but thought it's pretty similar. I have the WMH's with the pumps on my 91 200 Mariner. Think it's a WMH 6 or 7. Throttle response on the motor is immediate.

Been having a problem with a stripped thread on one of them (Idle Bleed jet, too small for helicoil) and looking to change it out, but can't find any with the pump. Can I simply replace with a later WMH without the pumps and any specific models better than others? Was wondering if I needed to do something with the timing etc..

Happy to start a new thread if needed.

Thanks

[Glastron1987]

Please use this thread. This is the stuff I was hoping for. I have WH-41's on my XR4, and have even rebuilt them, but really didn't know much about any of the differences among all the models. So you and mach have made a good start.

[Zoomba]

Have a nice set of 3 WMH 16s I bought, no pumps, supposedly from a 95 200, jetted .066 $100 for the set, plus the shipping. I only needed the manifold and reeds and I'm using a different carb set on my 88 motor. Dave Leonard

[TEXAS20225]

MACH 351 X2 the WMV are my favorite carb the 18's come with 82 mains in them from the factory they run great , the wmh 21 are my second favorite carb they are good carbs and the tune very well. The pumpers carbs dont need the pumpers fill them in with epoxy but if you must have them i have two sets of them for parts the WH carbs is real thirsty carbs and the easiest to work on

[powerabout]

what are the venturi sizes?
smallest Merc ever made and the largest?

[Glastron1987]

Interesting on the Wh's. I did find them easy to rebuild, and was wondering if newer models may be more fuel efficient.

[Zoomba]

Interesting on the Wh's. I did find them easy to rebuild, and was wondering if newer models may be more fuel efficient.

According to Chris Carson and his son, also T-rex, all regulars on this board and major motor builders; the short of it is to use WH 20's or WH46's WH 31's okay too, they all ran with 2.4 piston ported engines, and have low and high speed jets. They are easiest to jet for hi-po applications, partly because its been done so much that we can use their data to set up our jets.

WMH and WMV carbs are single float carbs, with or without accel pumps, they have 3 fuel circuits, low speed, mid , and high speed.

Some say they are more efficient, they have been mostly used on " behind the liner" ported engines, 2.5, 3.0 etc. According to the gurus, a 2.5 200 jetted .72 will run away from a 2.4 with .82 jets, so I am not sure if the carbs are the fuel efficiency or the porting design of the engine. Seems to me the Stoichimetric fuel/ air is the goal, so maybe the breathing difference is the port design, I have no fuel burn data so it is hard to calculate the " specific fuel consumption" based on jet sizing alone.

The WMH16 set I have is stock jetted @ .66" which is for a 200 hp 1995 2.5. Stock jetting for a 2.4 200 with wh31 carb is .72 I believe. They all told me not to run the wmh's as too lean without jet change. As no one seemed to know where to start jetting them for my application and since another $100 got me WH's that I knew where to jet, I figured that it was way cheaper than trying to figure it out myself with a burn down.

I have heard the wmh-s are pretty efficient, and I bet if we took the time to figure out jetting they would run nicely on a 2.4

In the "'history of the V6" sticky, the guy who designed the v6 Merc prefers the dual float design, especially in cornering.

As to bore size of carbs, I think there are 3 sizes, but it doesn't seem that they are dramatically different by more than .200'' or so. The 135s and 150s used the small ones, the large ones seem to be like 1.375 and the mid size seem like about 1.31" ish if memory serves

the ProMarine website has a nice application list for carbs and parts, you can pretty much tell which carbs are the same by seeing which ones the rebuild kits fit. the 1136 kit with floats and the 7005 gasket set seem to fit the majority of years of wh carbs, FWIW

I am jetting my wh31's .82 and .86", should be .84 but they don't make that size gas jet drill, so I'll either buy jets or just drill them .82 and .86 on cyls 2 and 5, which run leaner per the manual.

My engine is an '87 2.4 200 with enlarged piston ports, Land and Sea rods, and a cut exhaust chest, going to run small 150hp 2 pc heads with the hemi combustion chamber, which should be good for premium gas 93 octane, and 145 psi. Port height seems to be that of a stock 240 so not sure if engine has been ported and re nikasiled, as I got the powerhead in a trade.



I have an Carson intake spacer and 5 pedal sport glass reeds, and manifold from a 95 2.5, and I'm using the WH 31's and a Bobs machine shop tuner, no cross drilling on manifold, leaving the liner in the exhaust.

Hope it works well on my new to me 20' Sanger Alley Cat tunnel. Looking for 245 hp and 85 mph.

Dave

This is a pretty good thread on carbs over on http://www.corboatracing.com/mercury...etors-outboard ;

Regarding the carbs, I have tried many WH sets of carbs. I think they are all very similar but a few points to consider... Measure the Venturi sizes with a pair of inside calipers. The class size limit is 1.327 inches I believe. The WH carbs came in maybe two or three different sizes the ones you want should measure 1.315. I believe the rule is 1.327 to allow for manufacturing tolerances. Venturi size is the biggest difference/advantage between all the WH carbs. The idle circuits are also different but I don't see that making a big difference and I don't know the differences. The WH numbers also indicate jet sizes.

[TEXAS20225]

Major Motor builder ? i build 25/30 each year no 2.4 or 2.0 stuff all 2.5 or 3.0 the wmv carbs are much more fuel friendly, i personally do not like carbs 95 % of all i build is EFI i gave away at least 20 sets of various carbs to James Perry he likes them to each his own when i do build one its always late model carbs

[Zoomba]

Major Motor builder ? i build 25/30 each year no 2.4 or 2.0 stuff all 2.5 or 3.0 the wmv carbs are much more fuel friendly, i personally do not like carbs 95 % of all i build is EFI i gave away at least 20 sets of various carbs to James Perry he likes them to each his own when i do build one its always late model carbs

Well hey, I do one project a year, so 25 is pretty major to moi! Maybe major poster? Anyway love your writing and experimenting. I like carbs cause im cheeep!

[Zoomba]

Any guesses as to jetting the WMH16s for 2.4?

[Glastron1987]

Do either of these help if you look up parts for your engine?

http://www.boats.net/
http://www.marinepartsplus.com/

[Boulder]

Texas20225 , I have a 1991 Mariner 175hp. I have just rebuilt the WMH 2,11 Carbs ,they do have a accelerator pumps . Almost impossible to find parts for accelerator assembly, and cups are shoot. You stated it is possible to delete the accelerator pumps all together . I would like to do that. My concern is , will it bog down under fast acceleration , do I need to change out some jets ? Also, what epoxy would you suggest I use to fill the holes in the carb pump. Thx