Johnson 5.5 powerhead swap

[Super Sportster]

I've done the powerhead swap, a CD20 is replacing a CD15. I've swapped out the head and intake manifold. Problem is the thermostat. I now have an exposed hole in the block. If I tap the hole for a pipe plug and plug it off will I still have cooling circulation like the CD15 would have?

[Super Sportster]

The answer to my question is no but I found the fix. Upon further investigation the water inlet between the two blocks are the same. The discharge is different because of the thermostat so it actually is an easy fix. I drilled the passage that wasn't drilled in the late block as it is in the early block. So now I just need to plug the hole in the side of the late block like the early block is and plug the the thermostat hole. Water will flow now from the top of the block on the port side and discharge at the top of the block on the stbd side, just as the early block does.

[Super Sportster]

Good to go

I've installed a 7/16" soft plug into the block where I've drilled out the passage then tapped the open thermostat and threaded in a bolt with a copper sealing washer. I'll fire it off soon and see what happens!

[Super Sportster]

One more problem..............solved

Well I fired it off and discovered another hole that needed plugged. Cut a piece of brass round stock and plugged it. Fired it off again and it works!
I've had it idling for a couple hrs so I think cooling conversion is completed.
Now on to the mods to the carb so I can get the hood on.
[nomedia="http://www.youtube.com/watch?v=FSu0GhyrWls"]YouTube - MOV01229[/nomedia]

[Helmar]

Well I fired it off and discovered another hole that needed plugged. Cut a piece of brass round stock and plugged it. Fired it off again and it works!
I've had it idling for a couple hrs so I think cooling conversion is completed.
Now on to the mods to the carb so I can get the hood on.
YouTube - MOV01229

Thats the way to figure this stuff out. Just keep pecking away at it.

[Super Sportster]

Thats the way to figure this stuff out. Just keep pecking away at it.

Yep, I was told you can't interchange the heads from early to late. You know me, just tell me I can't do something! Mechanically it's now sound and functional. Cosmetically challenged. What the hell am I going to do with it? I have no idea, just a project for something to do I guess as if I didn't have enough of those already! Now I've got a couple motor mounts to send you!

[Helmar]

When someone tells me that something will not interchange or fit, I ask, Why first

[Tim McCrain]

Why not?

My approach to all of this is that it's supposed to be fun. At least for those of us who don't earn a living at it. If you enjoy doing it, then why not? It's not like we're destroying a classic Rolls, or the last '49 Cadillac in existence.

It's like the guys who build the scaled down V8s, they do it because it's FUN.



So Dick, what's next?

[Super Sportster]

I didn't ask why, I looked at the block and said why not. It's basically the same block with a material added for the thermostat. Comparing the two blocks and tracing the cooling flow revealed the undrilled passage in the late block. It then became easy. Just needed a steady hand and a watchful eye on the drill as there wasn't much room for a mistake hitting the water jacket!

Yep it was just for fun, a couple of engines that may have ended up in the scrap because of their individual problems, neither of any real value and even the finished project, it's just an old outboard that wouldn't bring much on the market. Might be good as trading stock, we'll see.

Next project......................I don't know, I should stay away from Craigslist!

[Tim McCrain]

saaayyy ...

If you have a thing for doing projects that others tell you can't be done, then ...

You can't sand all the old paint off my Bell Boy, it can't be done and you'd be foolish to try. :nono1: