# 30 Hp carb on a 25 Hp Evinrude



## lucescoflathead

I read somewhere you can increase the horse power of a 25 HP Evinrude by using a 30 HP carb. Is this true? I have a 25 HP 2 stroke that I thinks a 1979. I am going to go through it and thought about the carb replacement. Any thoughts? Thanks Todd


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## PartsMan

I looked on the Evinrude parts site.
https://shop2.evinrude.com/Index.aspx?s1=sh0gev1o4bpi95j2upihf6ada6&catalog_id=0&siteid=1
The 25 and 35 have the same intake so you could swap carbs,
but the 35 has a different gearbox and exhaust housing.


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## Lil' Blue Rude

The 20,25,30,35 all use the same powerhead but diffrent carbs. The exhaust might be diffrent on them to but I'm not for sure. The 30 hp and the 35hp carb will bolt up to your 25hp with no modification. It won't be a huge perfomance gain, around 500rpm but it will help pull a load better. You might use more gas depending on your set up. It won't be a big diffrence. It may help your gas milage to because the motor won't be working as hard pushing the boat. I would definatley change to a bigger carb, I would go for the bigger 35hp carb if it was me. Hope this helps you out some.


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## lucescoflathead

Thanks for the imput , guys.


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## nathanielrthomas

Does this same info apply to a 1992 Evinrude 25hp? Thanks


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## Lil' Blue Rude

Yep the same applies for the 92 25. bolts on with no mods.


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## gottafish

[-o< This is something I've wondered about for awhile also. I have one of the twin cylinder 15 HP Evinrude motors, the motor runs great but I wish it could have some help when my father and I go fishing. I have heard the the motors are basicly the same and all you would have to do is change carbs and maybe intake manifolds to get 18-20 HP out of one of these motors. Is this OK to do and cost effective at the sametime?


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## Lil' Blue Rude

Not queit the same deal withyour motor. [-X The 15hp motor is the same motor as the 9.9. They use the same block and a 2.188" or 2.375" piston depending on the year. The the 18-20hp your talking about is the 30hp model with a jet pump. The 18-35 are the same engine for the most part, they have some diffrences depending on the year but they all use a 3.00" piston. The 15hp motor uses a diffrent style carb then the 20hp-35hp motors. The 20-35hp use carb similair to that used on the 40hp twins to 60hp triples. It would shock me if you could rejet a 40hp-60hp carb to fit a 20-35hp motor. You would probably do other mods to the motor to be able to benifit from that size carb though.
In short 20hp carb won't bolt on to a 15hp motor, not saying it can't be acomplished with some mods, I've seen a guy but a 125hp carb on a 35hp omc on boatracingfacts so anything is possible.


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## zerofivenismo

Thanks for the helpful info Lil Blue Rude. I bought a '90 25hp rude OB over the summer and it came equipped with a 30hp carb. I just kind of blew off the notion that the carb increased the power output. Though performance gains may be small as you previously mentioned, it's good to know that the carb actually helps.


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## gottafish

Wow, thanks for the information.If switching carbs won't work, what do you suggest? Any help would be welcome.


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## Lil' Blue Rude

I don't know anything to do to the 15hp for more power, you might buy a set of boyseen reeds. I've heard of people changing props and your setup to gain some perfomance but I don't know anything about that because I run an outboard jet. These little motors have shocked me, I owned a 1983 9.9hp and I run it on a 8' 48" hydro plane I built and it would outrun a 40hp yamaha jet :mrgreen: That will put a smile on 14 year olds face ( and a frown on the other guys) :lol: Had some good times with that boat.


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## nathanielrthomas

Can this mod be done to a the 1992 25hp that has the primer system? Would you have to find a replacement carb that has the same primer system, or could you use one that has the older choke system? I know the carbs are the same other than the primer inlets....Thanks


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## nathanielrthomas

Can this mod be done to a the 1992 25hp that has the primer system? Would you have to find a replacement carb that has the same primer system, or could you use one that has the older choke system? I know the carbs are the same other than the primer inlets....Thanks


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## fastcajun

Change the exhaust also if you have the powerhead off and can afford it. That will help alot also. what goes in the motor must come out.


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## Skidz

Nathaniel, I have a 2000 25 Johnson with a primer system that I did this to, and it made a big difference. My original carb was part # 5000883, and I replaced it with a #0439377, 30 hp carb. I got these numbers off of evinrude.com, under the parts section. I cross refenced everything, intake manifold, primer, I even crossed the drive shaft numbers to make sure I wouldn't over load the gearcase. It bolted right up.

Before the swap, I was getting about 21 mph and 4900 rpms with a heavy, loaded 1648. Now, I am getting 25-26 mph, and just a hair under 5500 rpms (max for my motor). And, the OB was and still is set up about as optimum as possible.

It should be doable for you, just make sure to cross reference and be sure the rest of the OB can handle the extra ooomph!

Good luck!
Skidz


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## benjineer

Skidz,
I just responded to your post on Iboats. I'm glad to see you did the mod with good results. I'm running a 2003 25hp on mine and can get about 24mph with the stock prop. I don't have a tach, so I have no idea what I'm turning.


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## Skidz

Benjineer, thanks for the response. I'm still very pleased with my mod, and I can't tell any difference in fuel usage either. I highly recommend a tach, I use a tiny tach, it makes it much easier to know where you're at and where you want to go.


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## marcus123.11

:lol: im not sure if im in the correct place to talk about evinrude 35 hp 1977 ,i have a modified unit it has boysen reeds ,53mm exhaust outlet in the leg above the cavplat rejet carb and a fully lightend and ballanced crank and flywheel head skimmed to put compession at 160 psi its on a 14.6ft light weight deep v concorde fiesta speed boat v light boat i run a 10x13 alloy prop pollished on one side only at wot its revving sweetly at 7000rpm and sounds realy great when exhaust port is out of the water and nice and quiet when just moving around slow i have had it rev to 8500 when it jumped out of the water i know they used to race these engines so power to weight is why i did this mod , i would like to fit 40 carb but dont know any one who has done this ??


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## ulcer8

Does anybody know if this can be done to a 1964 Evinrude 18 hp Fastwin? I've got it on a 14 ft jon boat, but it's a heavy boat and I'd kill for some more speed out of that thing. [-o<


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