Another 20/25hp to 30/35hp Evinrude Johnson Conversion

[Rangernick]

Hey All

Im new to the forum and im sorry if im beating a dead horse here but I am working on converting my 1993 Johnson 20hp (J20CRLETS) to the 30/35 carb and intake. I could really use some help figuring out what years are compatible. I have read through every forum I can and most of the suggestions are just look at marineengine.com and such and compare part numbers. Im really racking my head trying to figure out what I need to compare and such. I could really use some help figuring what numbers will fit my 93'. I have found a guy with a intake and a carb off of a 78' 35hp he claims but im waiting to get part numbers from him. Will a 78' work? Im pretty lost here and desperately trying to learn! Also are evinrude and johnson interchangeable these years? If anyone flat out knows what years will work with my 93' that would be amazing. Also if anyone has the carb and intake for sale im looking!!

Thank you for any help ahead of time. It seems most of the conversion posts are quite old now so I hope im not annoying anyone! Ill attach some pictures of my current set up! Boat is a old 1448 Jon with pods and some upgrades!

 

[Weldorthemagnificent]

Less and less people run these older outboards. I currently run an 83' Johnson 35. I know that horsepower rating went from powerhead to propshaft around 84-85 and everything changed. For example, my 35 became a 30. I would be looking for parts from a later 80's to whenever they quit making them around 97 maybe when they changed to the 3 cylinder. There are still lots of these engines out there. Probably find a donor hanging out behind an old marina shop.

Sent from my CLT-L04 using Tapatalk

 

[Rangernick]

Thank you for the input! I am completely in love with these old tanks! I would like to pick up a couple of old parts motors because I honestly see no need for anything else on an old tin boat. Hopefully I can find something sitting in someone's old marina or backyard. Long live old OMC.

 

[Weldorthemagnificent]

They are great motors. The 521cc is about as bullet proof as you can get. I've had several from 20, 25 and 35. My favorite was the 93 25hp. It had electric start. I wish my current 35 did although it starts easily especially when warm.

Sent from my CLT-L04 using Tapatalk

 

[RaisedByWolves]

Best way to look for one is visual.

The 20/25 intakes are smaller than the 35 and restrict the air flow to the reeds.

This one is what you want. Note how the intake is nearly straight across the top and how the small flapper boss protrudes into the open portion of the intake.

Compare that to this which is a 25 hp intake.

 

[Rangernick]

Best way to look for one is visual.

The 20/25 intakes are smaller than the 35 and restrict the air flow to the reeds.

This one is what you want. Note how the intake is nearly straight across the top and how the small flapper boss protrudes into the open portion of the intake.

Compare that to this which is a 25 hp intake.

I have read into that but I did not get a great look side by side like that! Thank you for the post and info!!!

 

[Rangernick]

So the part number I come up with is 0396790. There sure are alot of the smaller intakes that come up when I search that number. Is that the correct number for the larger intake and these guys are just putting out misinformation? Or do I have the wrong intake number? Does anyone know the true intake number for the larger intake? From what im getting from looking up part numbers with years the 0396790 works from like 85'-94'? Some places say 85'-05' but in 95' they seem to have switched to the 3 cylinder?

 

[Pappy]

Let me clarify one point so far.
They never went to the 3-cylinder. The 3-cylinder was produced along with the existing 2-cylinder.

Now....there was a huge thread on this subject that should cover every single question you could possibly ask.
The horsepower change was in 1984, Went from powerhead rated to propshaft rated so you will see the 35hp turn into a 30 hp in later years Same engine.
Yes, Ev. And Jo. parts are interchangeable. Have fun....they really are pretty much bulletproof. Starting in around 1982 the gearcase joined the bulletproof part as well. It finally got all the bearings and modifications to the clutch dog it needed.

 

[Rangernick]

Let me clarify one point so far.
They never went to the 3-cylinder. The 3-cylinder was produced along with the existing 2-cylinder.

Now....there was a huge thread on this subject that should cover every single question you could possibly ask.
The horsepower change was in 1984, Went from powerhead rated to propshaft rated so you will see the 35hp turn into a 30 hp in later years Same engine.
Yes, Ev. And Jo. parts are interchangeable. Have fun....they really are pretty much bulletproof. Starting in around 1982 the gearcase joined the bulletproof part as well. It finally got all the bearings and modifications to the clutch dog it needed.

Thank you for clarifying some points. I have read and re-read through pretty much every single forum, facebook group, and youtube video I can possibly find over the last few weeks. Just trying to make sure I cover the right stuff for my 93' in particular! I really appreciate the input. Just trying to learn more for those that can spare the knowledge!

 

[Pappy]

Did you find the huge thread in this forum? It was about as thorough as you could possibly want.

 

[Rangernick]

Did you find the huge thread in this forum? It was about as thorough as you could possibly want.

https://forum.tinboats.net/viewtopic.php?t=23898

This one by Johny25? I have dug through each page of this one quite a bit and learned a lot from it! Extremely well done! Just doesn't help a lot with part numbers and he states later in the pages that he is unsure of how it fits up for 90's motors. Sure wish I could have a 5 minute chat with that guy!

Aside from that, I do think I have come up with the correct part numbers today! For my 93' with my primer style I believe I am looking for a Carb #439377/ #435376 and for my intake I believe I'm looking for #396790. Now the problem I'm finding is I have found lots of similar parts and lots of mix matched stuff =D> =D> Lots of places posting the smaller intake and calling it the #396790 (larger one). Always hard to do this online. Wish I hadn't moved away from a great OMC shop in my previous town. Its 5 hours away but would be much easier to match this stuff up in person now that I have an understanding of what I'm looking for! Might have to take the trip!

I think I have a good starting point of what I'm looking for. Will keep this post updated once I know more for the future 93'ers! Also I plan on taking a trip to the river to clock some before and after numbers for those interested!

 

[Pappy]

Overthinking this.
Any of the choke style carbs will work with the primer system or you can use the choke system with the addition of a choke solenoid and strap mount.
The purple/white lead that activates the primer will activate the choke just fine.
Want to use a choke style carb but use the primer instead? Just leave the choke blades open and use the primer.

 

[RaisedByWolves]

Did you find the huge thread in this forum? It was about as thorough as you could possibly want.

https://forum.tinboats.net/viewtopic.php?t=23898

This one by Johny25? I have dug through each page of this one quite a bit and learned a lot from it! Extremely well done! Just doesn't help a lot with part numbers and he states later in the pages that he is unsure of how it fits up for 90's motors. Sure wish I could have a 5 minute chat with that guy!

Aside from that, I do think I have come up with the correct part numbers today! For my 93' with my primer style I believe I am looking for a Carb #439377/ #435376 and for my intake I believe I'm looking for #396790. Now the problem I'm finding is I have found lots of similar parts and lots of mix matched stuff =D> =D> Lots of places posting the smaller intake and calling it the #396790 (larger one). Always hard to do this online. Wish I hadn't moved away from a great OMC shop in my previous town. Its 5 hours away but would be much easier to match this stuff up in person now that I have an understanding of what I'm looking for! Might have to take the trip!

I think I have a good starting point of what I'm looking for. Will keep this post updated once I know more for the future 93'ers! Also I plan on taking a trip to the river to clock some before and after numbers for those interested!

Searching by part number is very difficult, the reason for the pics I showed. With the pics you can scour e bay or the like and be sure of what you’re buying.

Some people will tell you the intake port is the only thing that matters, but it’s actually secondary to the larger intake volume and larger exposed reed area. One with the larger internal volume(reed area) will have the correct intake port.

I tried buying different carbs, many will work and the original 35 hp carbs are always way expensive. Mine is the upper? Carb off a 70hp but I disremember what year.

There is a thread on boatracingfacts.com I’ll post if I can find it that has more info.

Also, don’t waste your time polishing the inside of the intake like the one shown, it won’t do any good as it’s not a runner type intake.

Polishing a 2stroke is pointless as you want the turbulence to keep the air fuel mix atomized.

 

[RaisedByWolves]

Found it.

http://www.boatracingfacts.com/forums/showthread.php?15576-Evinrude-31-8ci-Mod-Advice

Read the entire thread before taking any of the advise. Let his mistakes work for you so you dont repeat them.

 

[Rangernick]

Found it.

http://www.boatracingfacts.com/forums/showthread.php?15576-Evinrude-31-8ci-Mod-Advice

Read the entire thread before taking any of the advise. Let his mistakes work for you so you dont repeat them.

Thank you so much for the help! Ill read that thread over a couple of times! I really appreciate everyone's advice! And that's a good tip to check out the 70hp carbs!

 

[RaisedByWolves]

Found it.

http://www.boatracingfacts.com/forums/showthread.php?15576-Evinrude-31-8ci-Mod-Advice

Read the entire thread before taking any of the advise. Let his mistakes work for you so you dont repeat them.

Thank you so much for the help! Ill read that thread over a couple of times! I really appreciate everyone's advice! And that's a good tip to check out the 70hp carbs!

Thanks for the thanks! The last time this topic came up it turned into a mess and I guarantee you that guys boat wasd going no faster than before his "Mods".

Theres a lot of bad info out there and its easy to go down a road (Stream?) and wind up with a motor that makes more noise but a boat that goes no faster. I reread both threads linked whenever I go about making any mods to an engine just as a refresher. The 55 and 70hp carbs need rejetted, but that is covered in the link I posted to the thread at BRF, as well as what carbs work somewhere near the end of the thread.

 

[Kismet]

Ain't no place quite like this place.

Nice work TinBoatians--TinBoaters, TinBoatistas... guys.

=D> =D> =D>

 

[Bign0703]

Found it.

http://www.boatracingfacts.com/forums/showthread.php?15576-Evinrude-31-8ci-Mod-Advice

Read the entire thread before taking any of the advise. Let his mistakes work for you so you dont repeat them.

Thank you so much for the help! Ill read that thread over a couple of times! I really appreciate everyone's advice! And that's a good tip to check out the 70hp carbs!

Where are you located? I'm I'm west tn and have some 35 parts. If your not too far I can check years and get info on them. Can also ship if need be.

 

[m48shooter]

Bign if he dose not want or need those 35hph parts i would happily buy them from you. I sent you a PM.

I have a 1996 25hp i would like to build up.