Question about Evinrude Carb compatibility?

The 35 should have a bigger throat size and a different size jet then the 25hp. It'll bolt on. You might have to remove the plate that the carb bolt to and enlarge the hole in it or change that plate to a 35hp plate. omc single barrel carbs from 25hp /75hp are interchangeable. Think there 3 diffent throat sizes and countless different models and layouts. So they'll all bolt on but you'd have to rejet for the motor. So you couldn't just bolt a 75hp on a 25hp without rejetting. But you can bolt the 35hp on the 25hp with out in jet changes. Sorry if I confused you any I know I'm rambling here.

[url=https://www.tinboats.net/forum/viewtopic.php?p=339411#p339411 said:

Lil' Blue Rude » Wed Jan 22, 2014 8:41 pm[/url]"]The 35 should have a bigger throat size and a different size jet then the 25hp. It'll bolt on. You might have to remove the plate that the carb bolt to and enlarge the hole in it or change that plate to a 35hp plate. omc single barrel carbs from 25hp /75hp are interchangeable. Think there 3 diffent throat sizes and countless different models and layouts. So they'll all bolt on but you'd have to rejet for the motor. So you couldn't just bolt a 75hp on a 25hp without rejetting. But you can bolt the 35hp on the 25hp with out in jet changes. Sorry if I confused you any I know I'm rambling here.

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Only slightly confused :lol:
So would you advise for or against buying the 1982 35hp Evinrude carb for my 1982 25hp Evinrude?
Originally I was told all I needed was a choke solenoid.
BUT, since I have a chance to buy both (aka carb & choke solenoid) NEW as a
package deal (online & at a real good price) well.. :-k
Anyways, are we talking major mods to get it to work properly?
You mentioned possibly having to change out the plates...?

You mentioned possibly having to change out the plates...?

Yeah,as mentioned the throat is larger. IIRC you're going have to change out the intake plate to allow for the larger volume of fuel / air mix. There's a thread on this site that explains it in detail. I've got a 35hp carb that I want to put on the 25. but still looking for a 35 parts motor to get the intake plate and other stuff.

found the thread, good reading n good info
https://www.tinboats.net/forum/viewtopic.php?f=4&t=23898

[url=https://www.tinboats.net/forum/viewtopic.php?p=339439#p339439 said:

Charger25 » Thu Jan 23, 2014 8:15 am[/url]"]You mentioned possibly having to change out the plates...?

Yeah,as mentioned the throat is larger. IIRC you're going have to change out the intake plate to allow for the larger volume of fuel / air mix. There's a thread on this site that explains it in detail. I've got a 35hp carb that I want to put on the 25. but still looking for a 35 parts motor to get the intake plate and other stuff.

found the thread, good reading n good info
https://www.tinboats.net/forum/viewtopic.php?f=4&t=23898

Click to expand...

I've seen other motor sites where guys actually enlarge the intake with a dremel. Pretty sure the 30hp motors use a 25 intake with the 35 carb.

[url=https://www.tinboats.net/forum/viewtopic.php?p=339439#p339439 said:

Charger25 » Thu Jan 23, 2014 8:15 am[/url]"]You mentioned possibly having to change out the plates...?

Yeah,as mentioned the throat is larger. IIRC you're going have to change out the intake plate to allow for the larger volume of fuel / air mix. There's a thread on this site that explains it in detail. I've got a 35hp carb that I want to put on the 25. but still looking for a 35 parts motor to get the intake plate and other stuff.
found the thread, good reading n good info
https://www.tinboats.net/forum/viewtopic.php?f=4&t=23898

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Thanks! :beer:
I PMed "Johny 25" & asked for his input also (hasn't replied back yet).
Btw, You wouldn't know a site that would give me details on the exact size of the throats of those two carbs would you?
That way I'll know for sure if I have to go hunting for a new plate or not.

[url=https://www.tinboats.net/forum/viewtopic.php?p=339393#p339393 said:

BloodStone » Wed Jan 22, 2014 3:31 pm[/url]"]Hello;
I was needing to know if there is ANY fundamental difference between a 1982 E25ECNE Evinrude CARBURETOR vs a 1982 E35ECND Evinrude CARBURETOR?
I've looked at exploded diagrams of both carbs & can't see a lick of difference between the two. Are they interchangeable?
I own the 25hp. Anyway, here's the link I went by..
https://www.boats.net/parts/detail/brp/B-0392570.html
Thanks in advance

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Not sure what year they changed, but I think your '82 actually has lots of differences from a 1982 35hp. Is your prop thru hub exhaust? If not then the 35hp will likely not do you much good due to the exhaust restrictions. Later in the 80's both the 25 and 35 used the same lowers, pretty sure yours did not.

Maybe this will help: https://www.tinboats.net/forum/viewtopic.php?f=4&t=23898.

[url=https://www.tinboats.net/forum/viewtopic.php?p=339648#p339648 said:

RStewart » Fri Jan 24, 2014 9:45 pm[/url]"]Maybe this will help: https://www.tinboats.net/forum/viewtopic.php?f=4&t=23898.

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Charger25 already posted that link, but i'm pretty sure that is not the same as his motor.

If you go to the link you will see the motor is a 25 that has a thru hub exhaust, same as a 35hp of the same year.

The 1982 35hp also has this same lower unit, but if his 25hp is a 1982 it should have the below pictured lower unit.

1982 25hp lower unit:
https://cdn.boats.net/diagram/brp/IMAGES/392976/24.png

1982 35hp lower unit:
https://cdn.boats.net/diagram/brp/IMAGES/392977/20.png

notice the difference

Not sure what year they changed, but I think your '82 actually has lots of differences from a 1982 35hp. Is your prop thru hub exhaust? If not then the 35hp will likely not do you much good due to the exhaust restrictions. Later in the 80's both the 25 and 35 used the same lowers, pretty sure yours did not.

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Now I am confused. :?
So MD Crappie, you're saying that 1982 E35ECND Evinrude carb will not work on my 1982 E25ECNE Evinrude motor
even though I can't see a lick of difference between the two carbs (maybe throat size?)?
And that somehow the difference in exhaust systems is the culprit? I'm pretty sure my 25 is NOT a thru hub exhaust.
I don't follow...But then again I'm a tinkerer not a full blown marine mechanic. So put it in layman's terms.

Ok it has been awhile so bare with me....so first things first as stated above the difference in the carburetors that gives the performance from the 25 to the 35hp in that year is the size of the venturi (throat) which allows more air to be sucked in. And the other difference as also stated above is jet size in the carbs. When you suck more air you need more fuel....and the 35hp carb had larger jets, simple as that.

As far as your gear case......you have the split gear case non-thru hub exhaust in 1982 on a 25hp. the 35's had the larger thru hub exhaust. It was in 1985 when OMC started using the lager gear case on all 20-25-30hp models and did away with the split gear case in that motor size. This is what yours should look like and your exhaust comes out of the blue circle I made. the red circle was already on this pic I found and is just a weep hole

And to the post regarding the dremel tool to bore out the intake.......this is usually done on the 1985 and on 20hp restricted intakes or the derated models. They made these intakes with a small hole to restrict airflow and keep the engine from making 25hp so it could go on lakes designated for 20hp or less. I had one of the 20hp models from 1985 (canada derated) and all you had to do to get 25hp out of it was bore out the intake hole. But to actually get the correct air flow volume it is virtually impossible to bore out the 25hp intake to match the size of the 30 and 35hp intakes. Well unless you have a CNC machine or something.

(My old computer crashed and I am in the process of trying to recover all my pics)

[url=https://www.tinboats.net/forum/viewtopic.php?p=339667#p339667 said:

BloodStone » Sat Jan 25, 2014 2:39 am[/url]"]

Not sure what year they changed, but I think your '82 actually has lots of differences from a 1982 35hp. Is your prop thru hub exhaust? If not then the 35hp will likely not do you much good due to the exhaust restrictions. Later in the 80's both the 25 and 35 used the same lowers, pretty sure yours did not.

Click to expand...

Now I am confused. :?
So MD Crappie, you're saying that 1982 E35ECND Evinrude carb will not work on my 1982 E25ECNE Evinrude motor
even though I can't see a lick of difference between the two carbs (maybe throat size?)?
And that somehow the difference in exhaust systems is the culprit? I'm pretty sure my 25 is NOT a thru hub exhaust.
I don't follow...But then again I'm a tinkerer not a full blown marine mechanic. So put it in layman's terms.

Click to expand...

The 35 carb will "fit" on your 25, but you will not see the gains that someone would see doing this to one of the (84-85) and forward models that have the thru hub exhaust. In fact you will, IMHO, see no gain at all. I believe it will actually run worse in the mid-range.

Before you "waste" any money on that motor I would go thru the exploded parts diagrams and see ALL of the differences.

Most guys don't realize all the parts that are different on the pre '84 motors. Look at the crankcase & cylinder heads, they the same? Nope

Part's 1 & 14 on each of the below diagrams:
https://cdn.boats.net/diagram/brp/IMAGES/392976/18.png
https://cdn.boats.net/diagram/brp/IMAGES/392977/16.png

The 35 carb will "fit" on your 25, but you will not see the gains that someone would see doing this to one of the (84-85) and forward models that have the thru hub exhaust. In fact you will, IMHO, see no gain at all. I believe it will actually run worse in the mid-range.
Before you "waste" any money on that motor I would go thru the exploded parts diagrams and see ALL of the differences.
Most guys don't realize all the parts that are different on the pre '84 motors. Look at the crankcase & cylinder heads, they the same? Nope
Part's 1 & 14 on each of the below diagrams:
https://cdn.boats.net/diagram/brp/IMAGES/392976/18.png
https://cdn.boats.net/diagram/brp/IMAGES/392977/16.png

Click to expand...

Oh crap! ](*,) Well better I found out BEFORE I bought it then after.
And here I was hoping that I found the pot of OB gold at the end of the proverbial rainbow.
So IF I am reading this right MD, #1) There's No practical way of boosting performance or HP on my 25 1982 Evinrude (#25ECNE), correct?
2) I have to find THE EXACT same carb that is currently on the motor? Originally, all I was told I needed was a choke solenoid (motor doesn't run correctly at WOT-needs to be manually choked & coaxed). So how wide open are my options just on that front (aka which Evinrude/Johnson models from 82-83 use the same choke solenoid)?
Thanks again to you & Johny25 for your help btw. You both just saved me from making a $140.00 mistake :beer:

[url=https://www.tinboats.net/forum/viewtopic.php?p=339717#p339717 said:

BloodStone » Sat Jan 25, 2014 2:12 pm[/url]"]

Oh crap! ](*,) Well better I found out BEFORE I bought it then after.
And here I was hoping that I found the pot of OB gold at the end of the proverbial rainbow.
So IF I am reading this right MD, #1) There's No practical way of boosting performance or HP on my 25 1982 Evinrude (#25ECNE), correct?
2) I have to find THE EXACT same carb that is currently on the motor? Originally, all I was told I needed was a choke solenoid (motor doesn't run correctly at WOT-needs to be manually choked & coaxed). So how wide open are my options just on that front (aka which Evinrude/Johnson models from 82-83 use the same choke solenoid)?
Thanks again to you & Johny25 for your help btw. You both just saved me from making a $140.00 mistake :beer:

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Well your choke/solenoid should have nothing to do with WOT running, unless it is somehow closing on it's own. If this were happening then the motor would die from lack of air.

Since you have one of the older ones (choke vs primer) your choke should only be closed when you are warming the motor up. Once the motor is warm the choke should just be open. If you are having to close the choke while running then it is like you are sucking air from one of the carb seals/gaskets or core plugs. If this is happening at WOT then you likely are not able to get it to stabilize at idle.

[url=https://www.tinboats.net/forum/viewtopic.php?p=339717#p339717 said:

BloodStone » Today, 11:12[/url]"]

The 35 carb will "fit" on your 25, but you will not see the gains that someone would see doing this to one of the (84-85) and forward models that have the thru hub exhaust. In fact you will, IMHO, see no gain at all. I believe it will actually run worse in the mid-range.
Before you "waste" any money on that motor I would go thru the exploded parts diagrams and see ALL of the differences.
Most guys don't realize all the parts that are different on the pre '84 motors. Look at the crankcase & cylinder heads, they the same? Nope
Part's 1 & 14 on each of the below diagrams:
https://cdn.boats.net/diagram/brp/IMAGES/392976/18.png
https://cdn.boats.net/diagram/brp/IMAGES/392977/16.png

Click to expand...

Oh crap! ](*,) Well better I found out BEFORE I bought it then after.
And here I was hoping that I found the pot of OB gold at the end of the proverbial rainbow.
So IF I am reading this right MD, #1) There's No practical way of boosting performance or HP on my 25 1982 Evinrude (#25ECNE), correct?
2) I have to find THE EXACT same carb that is currently on the motor? Originally, all I was told I needed was a choke solenoid (motor doesn't run correctly at WOT-needs to be manually choked & coaxed). So how wide open are my options just on that front (aka which Evinrude/Johnson models from 82-83 use the same choke solenoid)?
Thanks again to you & Johny25 for your help btw. You both just saved me from making a $140.00 mistake :beer:

Click to expand...

Listen to those that have done it.....not those that talk about doing it. I know of several guys that have done this mod to the pre 84' 25hp's and had very good results. It will take me a little bit to find them......some are on this site and I hope they see this post. Others are on different sites and I will try to get the info to you

Well your choke/solenoid should have nothing to do with WOT running, unless it is somehow closing on it's own. If this were happening then the motor would die from lack of air.

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I have both an electric choke & a manual choke (knob pull out on front of engine). I am talking about the round cylinder attached to the side of the carb with the 2 wires coming off it & the small rod running through the middle. I was told by a mechanic that that was the culprit. So I am taking his word for it.

Since you have one of the older ones (choke vs primer) your choke should only be closed when you are warming the motor up. Once the motor is warm the choke should just be open. If you are having to close the choke while running then it is like you are sucking air from one of the carb seals/gaskets or core plugs. If this is happening at WOT then you likely are not able to get it to stabilize at idle.

Click to expand...

It idles ok (not great) but when I pull up on the choke toggle located on the shifter box (side console) at WOT the motor definitely picks up speed & runs better.
Anyway question MD; Are you speaking from experience having done these specific carb mods or are you merely guessing/deducing that it won't work?
(no offense meant or implied)
I still don't know how it matters where the exhaust is (thru hub or otherwise) in regards to these carburetors? :?:

[url=https://www.tinboats.net/forum/viewtopic.php?p=339742#p339742 said:

BloodStone » Sat Jan 25, 2014 6:35 pm[/url]"]
I have both an electric choke & a manual choke (knob pull out on front of engine). I am talking about the round cylinder attached to the side of the carb with the 2 wires coming off it & the small rod running through the middle. I was told by a mechanic that that was the culprit. So I am taking his word for it.

Click to expand...

I would find a new mechanic. That is the solenoid that closes the choke. If closing the choke at high speed helps you, you have carb problems, not a choke problem.

It idles ok (not great) but when I pull up on the choke toggle located on the shifter box (side console) at WOT the motor definitely picks up speed & runs better.
Anyway question MD; Are you speaking from experience having done these specific carb mods or are you merely guessing/deducing that it won't work? (no offense meant or implied)
I still don't know how it matters where the exhaust is in regards to these carburetors? :?: [/b]

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No I have never done the "conversion". I was just letting you know that there are more differences then "just the carb". Lots of guys think the pre 84 motor are just like the 84 and up. All I am saying is that you should look at the diagrams real good before taking the leap on a carb. I'm fairly confident you will need to do a bunch more things then just bolting on a carb to change your 25 to a 35.

Another thing to think about is your LU. Will it handle 35hp like the larger one? What props are available for it? Can you get a bigger prop if the 35hp will allow you to spin more RPM? or are you planning to just spin the stock prop faster?

It's not where the exhaust it, it how much exhaust is able to get out. Just take to anybody who works on motors. Doesn't matter how much gas/air you put in, if you can't get the exhaust out the HP is not increasing.

I would find a new mechanic. That is the solenoid that closes the choke. If closing the choke at high speed helps you, you have carb problems, not a choke problem.

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Yeah, good luck with that! :roll: And you're probably right, that's why I would like to replace the **** thing altogether (thus my initial inquiry post here).

No I have never done the "conversion". I was just letting you know that there are more differences then "just the carb". Lots of guys think the pre 84 motor are just like the 84 and up. All I am saying is that you should look at the diagrams real good before taking the leap on a carb. I'm fairly confident you will need to do a bunch more things then just bolting on a carb to change your 25 to a 35.
Another thing to think about is your LU. Will it handle 35hp like the larger one? What props are available for it? Can you get a bigger prop if the 35hp will allow you to spin more RPM? or are you planning to just spin the stock prop faster?
It's not where the exhaust it, it how much exhaust is able to get out. Just take to anybody who works on motors. Doesn't matter how much gas/air you put in, if you can't get the exhaust out the HP is not increasing.

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I just brought a new prop for it a couple of years ago & it still looks great. I'm not looking for an increase to 35hp
(I'd be content with a mere 5hp increase & a smooth & correctly running OB at this point).
In regards to your other questions, I don't know. But I doubt an additional 5-6hp is going to have THAT dramatic an effect on my LU.
Just like I don't know between what you're saying & what Johny 25 is saying? He says he has proof based on others having done it.
I just don't want to get involved in some deep, total tear down mechanical BS in order for this conversion to work.
If all is required is a new plate & fine tuning the 35 carb, then great! If I gotta change a bunch of other stuff too (like LU & exhaust ports etc..), then no!

[url=https://www.tinboats.net/forum/viewtopic.php?p=339747#p339747 said:

BloodStone » Sat Jan 25, 2014 7:23 pm[/url]"]
In regards to your other questions, I don't know. But I doubt an additional 5-6hp is going to have THAT dramatic an effect on my LU.
Just like I don't know between what you're saying & what Johny 25 is saying? He says he has proof based on others having done it.
I just don't want to get involved in some deep, total tear down mechanical BS in order for this conversion to work.
If all is required is a new plate & fine tuning the 35 carb, then great! If I gotta change a bunch of other stuff too (like LU & exhaust ports etc..), then no![/b]

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I think this might be one of the "conversions" he is speaking of:
https://www.tinboats.net/forum/viewtopic.php?f=4&t=26524&p=272117&hilit=+35hp#p272117

Here is the motor his carb came from - a 1980 35hp
https://www.boats.net/parts/search/BRP/JOHNSON/1980/J35ECSM/CYLINDER%20%26%20CRANKCASE/parts.html

Here is the motor he put the carb on - a 1980 25hp
https://www.boats.net/parts/search/BRP/JOHNSON/1980/J25RCSA/CYLINDER%20%26%20CRANKCASE/parts.html

Look at part #'s 1 and 14 - the "Cylinder & Crankcase Assembly" and the "Cylinder Head Assembly"
Both motors use the same one of each.

Now look at the 1982 25hp below
https://www.boats.net/parts/search/BRP/EVINRUDE/1982/E25CNE/CYLINDER%20%26%20CRANKCASE/parts.html

and compare it to the 1982 35hp below
https://www.boats.net/parts/search/BRP/EVINRUDE/1982/E35ECND/CYLINDER%20%26%20CRANKCASE/parts.html

Notice that they are different?

I see what you are trying to say MDcrappie but believe me both those blocks are the exact same and came front the same cast, cylinder heads too. There is nothing different internally on them at all. Just look........they put different numbers on replacement parts but they are the same and match the 25hp
https://www.marineengine.com/parts/johnson-evinrude-parts.php?year=1982&hp=35&model=E35ELCND&manufacturer=Evinrude&section=Cylinder+%26amp%3B+Crankcase