So I was curious to see if a 1975 25 HP Johnson could be converted to a 35 HP by changing out the intake manifold and carb since that can be done with later models in the 80s. The 1975 series doesn't have a 35 HP model, but the 1976 series DOES have a 35 HP model. I've seen topics here that the conversion would work with the later 70s models too, specifically 1976 and later when they switched from the points and magneto ignition to the CDI ignition system.
I took a look at these 2 schematics for the 1975 intake manifold and the 1976 intake manifold and they are exactly identical.
1975 25 HP Intake Manifold Schematic
See attachment below
1976 25 HP Intake Manifold Schematic
See attachment below
Then I took a look at the 1976 35 HP Intake manifold schematic, it seems like there other parts other then the intake manifold that I might have to replace, including the leaf plate and intake manifold gasket, they are of a different design then the 1976 25 HP model. In the topics I link too below it seems to be the consensus that all that would need to be replaced to do this conversion would be to replace the intake manifold itself and the carb from the 35 HP model. Can I just leave the leaf plate and gasket from the 25 HP model, or do I need to buy the 35 HP leaf plate and gasket IN ADDITION to the carb and intake manifold? Does the different leaf plate design not effect this conversion?
1976 35 HP Intake Manifold Schematic
See attachment below
Many topics that cover the conversion process mention that the only thing that's needed is to throw on a the 35 HP Carb and Intake manifold for this to work. Is it necessary in my case to buy additional parts, other then just the 35 HP intake manifold and the 35 HP carb to do the conversion on a 1975? Do I need to buy the 1976 35 HP gasket and leaf plate in addition to the intake manifold, or can I just use the gasket and leaf plate that's currently on my 1975 25 HP Johnson? Also what model years use the 0386792 35 HP Intake Manifold and the 0387271 35 HP carb? Do both Johnson and Evinrude 35 HP motors use the same exact parts?
For reference I'm attaching a link to two different articles that cover this topic more in depth
80's Johnson/Evinrude 25hp to 30-35hp conversion with pics
http://forums.iboats.com/forum/engin...sion-with-pics
Tinboats Johnson/Evinrude 25hp to 30-35hp conversion with pics
http://www.tinboats.net/forum/viewto...0c374e96048cfd
I took a look at these 2 schematics for the 1975 intake manifold and the 1976 intake manifold and they are exactly identical.
1975 25 HP Intake Manifold Schematic
See attachment below
1976 25 HP Intake Manifold Schematic
See attachment below
Then I took a look at the 1976 35 HP Intake manifold schematic, it seems like there other parts other then the intake manifold that I might have to replace, including the leaf plate and intake manifold gasket, they are of a different design then the 1976 25 HP model. In the topics I link too below it seems to be the consensus that all that would need to be replaced to do this conversion would be to replace the intake manifold itself and the carb from the 35 HP model. Can I just leave the leaf plate and gasket from the 25 HP model, or do I need to buy the 35 HP leaf plate and gasket IN ADDITION to the carb and intake manifold? Does the different leaf plate design not effect this conversion?
1976 35 HP Intake Manifold Schematic
See attachment below
Many topics that cover the conversion process mention that the only thing that's needed is to throw on a the 35 HP Carb and Intake manifold for this to work. Is it necessary in my case to buy additional parts, other then just the 35 HP intake manifold and the 35 HP carb to do the conversion on a 1975? Do I need to buy the 1976 35 HP gasket and leaf plate in addition to the intake manifold, or can I just use the gasket and leaf plate that's currently on my 1975 25 HP Johnson? Also what model years use the 0386792 35 HP Intake Manifold and the 0387271 35 HP carb? Do both Johnson and Evinrude 35 HP motors use the same exact parts?
For reference I'm attaching a link to two different articles that cover this topic more in depth
80's Johnson/Evinrude 25hp to 30-35hp conversion with pics
http://forums.iboats.com/forum/engin...sion-with-pics
Tinboats Johnson/Evinrude 25hp to 30-35hp conversion with pics
http://www.tinboats.net/forum/viewto...0c374e96048cfd
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