Mercury 40 3 cylinder.

**Shallow Runner** · 04-10-2013, 03:21 PM

I have a mercury 40 ELPTO. It's a 3 cylinder 2 stroke. I have researched carbs and reed plates for 40 and 50 hp motors and most parts are the same. The differences I can find are the 40 has a restrictor behind the reed plate and the 50 does not. The 40 has .48 jets and the 50 has .52 jets. The carbs themselves have different part #s but all the internals are the same part #. I was wondering if one of you Merc. gurus could tell me whether its as simple as pulling the restrictor plate and swapping jets. Or does the 40 and 50 carbs have a different throat diameter and butterfly.

**Cray** · 04-10-2013, 05:38 PM

I would say you could remove the Restrictor rejet Carb and gain some performance. Maybe not all the way to 50 but probably 45 or so. Im betting they have a smaller throat but not by much. That restrictor is the big thing.

**Barnacle Bill** · 04-10-2013, 05:54 PM

Be sure to compare all the exhaust parts too. If you put more in you have to be able to get more out.

**Shallow Runner** · 04-10-2013, 11:24 PM

I've done that as well Mr. Bill, same parts.

**Shallow Runner** · 04-11-2013, 12:10 PM

Cray, I did some further research today. The valve throttle, (Butterfly) where I'm from, is the same part # on the 40 as the 50. I'm guessing the I.D. will mic. the same on both carbs? Maybe the Venturi's are different?? Also correction on the jets 40= .044 not 48.

**Cray** · 04-11-2013, 05:51 PM

There may not be any difference in carbs then. They could be just using different part number because of jet size required. Lots of that done because of assembly line process. It's a Butterfly to me to

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