WH Carburetors: Mercury V6 Outboard

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Are all the Mercury WH series carbs with 1.327 inch venturis the same or do they differ? T-Rex and others on the boards such as Scream and Fly seem to claim the WH-15, WH-20, WH-22, and maybe the WH-46s are the best. The part numbers for the throttle body and bowls all appear to be the same. The butterfly's and the jets are certainly different. I believe they are all the same otherwise... So for all those who know, what do you know?

05's picture

Can someone extend on this before I,ll go and make multiple trips to the lake and countles hours on swiching carbs, I have 6 diferent sets for the NEW # 04 Baker, if you dont whant to share what works for you, all I need is some real tecnical information on the diferance on all WH-
Thank you.

007's picture

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. I always start rich. If your manifold is cross-drilled, try .098 or .096 jets to start. If your manifold is NOT cross-drilled, maybe you will want to run .088 jets. Others may go leaner but I have not seen lean mean faster. Cross-drill is worth one or two mph but maybe you lose some acceleration.

007's picture

Just picked up a set of the WH-20 carburetors for my 2.4 Liter ski boat and they do have a larger venturi size, around 1.375, too larger and not legal for the COR class.

05's picture

My understanding is that the 22 are better for drag racing and the 46 are better for circle racing, what about the WMH? I have seen all on some of the leading boats. HAPPY FATHERS DAY TO MIKE and all off you.

007's picture

Happy Father's Day from K1 Speed. Regarding the all the later WH carbs with the COR legal 1.327 Venturi... Including the 22s, 46, 40s, they all look to be exactly the same accept for the original jet sizes. I have not found any difference but would be interested in what others might say. The WMV seem the same but less reliable in starting and the corners... Maybe? I believe the WMH might be the carbs with the accelerator pump? That might be worth a test?

Capnzee88's picture

have a set of the carbs with the acc. pumps--made one year only (to my knowedge) came on my originalsst-120 engine. don't like ,,will sellcheap--u name price-if somewhat reasonable, i'll take it

007's picture

Mercury WH carbs with 1374-5427 part number cast into the throttle boy (upper half of the carb) should have the 1.315 venturi. Mercury made two other sized carburetors in the WH series... a smaller 1.0 inch venturi and a larger 1.375 (??) venturi.

The -numbers seem to indicate which jets came in the carbs and small differences in the idle circuits but they are mostly the same.

The 22s, 40s, 46s, and most others should be 1.315 inch. The class limit allows up to 1.327 inch, just like the SST-120 class, for casting differences, so the 1.315 sized carbs are the ones to run in COR.

1382-6425 carbs are the smaller 1.0 inch Venturi which are legal in COR.

1386-7598 castings are the larger 1.375 (??) inch Venturi which are NOT legal in COR. The WH-20s have this number (and I believe the WH-15s) and are outside of the legal limit for the COR class.

DaBull's picture

This makes it all somewhat clearer for me now.