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Thread: 40hp Merc 52ci mod help

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    Default 40hp Merc 52ci mod help

    Does anyone know much about a 3cyl 52ci Merc 40? iíve got a 97 that iím hoping there are some easy mods like changing out carbs to bump of the HP on.

    from what I can tell it is a bit of an odd motor, looks like in 96 and the first part of 97 the 40hp was a 4 cylinder and then in 98 is when Mercury switched to the 3cyl 59ci 40,50, and 60. In 91-97 they had a 3cyl 50 and 60 that were both 52ci. Anyone have any clue what the difference is between my 97 40 and those?

    Appreciate any advice!

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    Put up some pics of it, I don't think the 52" was available as a 40 unless it was a jet, and if it was a jet motor it most likely has 60 carbs. Pics of carbs too, I should be able to tell what you have from the numbers on them.

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    Quote Originally Posted by hightide View Post
    ...and if it was a jet motor it most likely has 60 carbs.
    AND, if it was a factory jet, it's got a 15" exhaust tower, too. That would be cool.

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    I had a 1993 or 1992 mariner same as merc 52ci 60hp tiller short short shaft for a while. I converted it to a jet making it a 60/40. like others have said I don't believe merc sold a 40hp 3cyl till they came out with the 59ci triples. I could be wrong maybe there were a few anomalies towards to the tail end of the 52ci triples. But far as I know the only factory 3cyl 52ci mercs sold as 40hp were usually sold from the factory with a jet which I believe those were marketed as 45hp jets. They had the same power head as 60hp props jets aren't as efficient as props and lose some power at the jet. So when sold as jet factory they were sold as 45hp maybe some labeled as 40hp which is a 60/40 jet. Pics of the motor and cowling would help, who knows maybe it was a 50 or 60 and someone just put different decals on hard to say. I ended up selling my 52ci merc 60hp with the jet on it and sold the short shaft lower unit seperately. I've always been more of an omc guy and now have an omc 56ci triple. The turn off on the merc for me was the blind bore no cylinder head to shave that makes bumping up compression expensive because you pretty well are limited to going to different pistons to bump up compression to go along with different porting for performance gains. If it is a 40hp and has smaller carbs you could go to 60hp carbs and better reeds that would be your easiest quick gain of some ponies.

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    Here is a picture of the serial numbers off of the carbs and of the plate on the motor. Sorry that took a bit the boats in my family’s barn and I’m off at school at the moment

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    You sure it's a 52? But either way those aren't 60s. You would see some benefit going to a set of 60 carbs, preferably the 3301-824854c series ones. Put up a pic of the whole motor, might be a 59

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    In regards to these carbs (all Merc carbs for 2stroke midrange engines), are there specs available for venturi size and jetting based on the casting numbers, or based on the the dot-peen'd "WME##-#" numbers?

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    There are some early 52ci 60 carbs that don’t seem to perform as well think their number is 706826, they have a shorter emulsion tube and use a .070 jet stock. 824854c is the revised carb and takes a .062 jet for the 52”. 824854c1 is the 59” designation and uses a .060 main. Venturis are all the same. I’ve never been able to make much sense of the peened numbers, this is going by the castings

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    Thanks for all the info, I really appreciate all the help. I’m pretty new to this but want to figure it out cause so far I have really enjoyed it. Do changing the the jets make much of a difference? I run the boat at pretty low elevation for Colorado (~4000ft) but that’s probably still considered pretty high for most of the country. I know with dirt bikes they won’t run right until you lean them out a bit, can you do that with an outboard?

    Also I should be able to get some better pictures of the motor either tomorrow or Friday. What made me originally think it was a 52ci instead of a 59 was that the cowling is different. All of 59s I’ve seen have an oiler window, also mine has both pull and electric start which I haven’t ever seen on a 59.

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    There were quite a few 59" 40s made with pull start, I've got 2 of em. A pull start 52" is actually really rare, especially in america. Get a set of 824854c1 carbs and a set of .058 jets, they're safe to run at sea level but a step down from stock. You'll want to get a set of 50/60 reed retainers to get rid of the 40 stops.

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