carburetor swap

[sinkhole]

Can you swap a carb. from a 25 1974 hp Johnson for a carb. from a 20 1975 hp Evinrude? Not concerned with speed or oower loss. Thanks.

 

[saltchuckmatt]

Easiest answer here is, do you have each carb? Just try it, I'd have that test completed for in about 1 hour...if it takes you two your still okay.

Key words here are "I don't care about speed or loss of power"

 

[saltchuckmatt]

I could find a 1975 20 hp...only a 25.

 

[sinkhole]

Easiest answer here is, do you have each carb? Just try it, I'd have that test completed for in about 1 hour...if it takes you two your still okay.

Key words here are "I don't care about speed or loss of power"

I do have both carbs. I will change them over reaso being I want to keep the 25 hp it's electric start Would I have to change any jets?

 

[kbait]

Jet size is matched to carb throat diameter (air intake/flow), so each carb already has correct jet. 20hp was likely made in Canada.

 

[saltchuckmatt]

Jet size is matched to carb throat diameter (air intake/flow), so each carb already has correct jet. 20hp was likely made in Canada.

Kbait, good to know. Did not no Canadians had their own line.

 

[racerone]

The 22 cube engine that was developed in the mid 50's was marketed to 1976 as 18 / 20 / 25 HP .----25 HP started in 1969 to 76.------But this 22 cube engine was offered in Canada only for a few more years after 76 as a 20 HP.-----Top secret and not listed unless you have local knowledge and the old " micro fiche cards " and the reader.

 

[saltchuckmatt]

And that's the way the cookie crumbles.

Just try the carb.

 

[tphoyt]

A friend of mine still relies on micro fiche to this day from time to time and he’s dam proud of that set up.

 

[racerone]

I guess it can't be lost because somebody pulled the wrong switch somewhere.-----The only drawback is that 30 year old cards are not updated with superceded part numbers.

 

[saltchuckmatt]

I'm a general contactor and have been one since 1989. I remember all the years going down to the building department to look at plans on that wonderful machine.

Thinking back on it now I'm glad we have it but what a complete waste of time compared to today's modern standards.

The only microfiche I go get now I suppose, would be called massive fish.



Just call me SaltChuckGrouchoMarx.

PS, Tim...That's for you baby!

 

[jimmbo]

While it was possible to turn a 22 inch 18/20 into a 25, it was more than a Carb Swap. Intake Manifold was different, so were the Pistons, Cylinder Head, Crankshaft, and Throttle Cam on the Armature Plate.
The Pistons had the Pin in a Location closer to the Crown, this changed the Port Timing, but also lowered the Compression, so a Head with a Smaller Chamber was needed to restore the Compression. Crankshaft on the 25 was a better balanced version. More than one Person has just put the 25hp Cylinder Head on an 18/20hp, and destroyed it due to Detonation. That head requires the proper Piston

Just putting a 25 Carb on an 18/20, usually results in a Engine that has throttle Response Issues, making it less fun to operate

 

[saltchuckmatt]

Agreed, always, always,best to stay stock...but what a learning experience for the original poster and by luck it may work out.

 

[sinkhole]

Agreed, always, always,best to stay stock...but what a learning experience for the original poster and by luck it may work out.

While it was possible to turn a 22 inch 18/20 into a 25, it was more than a Carb Swap. Intake Manifold was different, so were the Pistons, Cylinder Head, Crankshaft, and Throttle Cam on the Armature Plate.
The Pistons had the Pin in a Location closer to the Crown, this changed the Port Timing, but also lowered the Compression, so a Head with a Smaller Chamber was needed to restore the Compression. Crankshaft on the 25 was a better balanced version. More than one Person has just put the 25hp Cylinder Head on an 18/20hp, and destroyed it due to Detonation. That head requires the proper Piston

Just putting a 25 Carb on an 18/20, usually results in a Engine that has throttle Response Issues, making it less fun to operate

 

[sinkhole]

Was asking if 20 hp carb could be put on a 25 hp motorÉ not other way round.

 

[jimmbo]

While it will bolt on, I wouldn't recommend it

 

[sinkhole]

While it will bolt on, I wouldn't recommend it

I did swap carbs but cannot get it to idle or stop sneezing. Was that the reason you wouldn't recommend it?

 

[jimmbo]

No, it is not the Size, Airflow wise, that the Engine was designed for. Incorrect Carb size, and resulting improper operation, make an Engine a Chore to Operate, if it even runs. But some people have to Experience the Problems/Issues themselves....

 

[sinkhole]

No, it is not the Size, Airflow wise, that the Engine was designed for. Incorrect Carb size, and resulting improper operation, make an Engine a Chore to Operate, if it even runs. But some people have to Experience the Problems/Issues themselves....

thanks for reply. I. will try to repair the 25 hp carb. & reinstall

 

[saltchuckmatt]

Or buy a used one....Tim's outboard in the mid West is great. Phone number and place are posted above the thread regarding where to buy used outboard parts.

Then you have two and your golden. Parts galore.