Johnson A series cooling

[adam1961]

I have a Johnson A that I have just re-assembled after going through it completely. It start, runs and idles very well. The only issue that I am having is with cooling on the port side cylinder. It seems to be getting very hot. I have a nice stream of water out of the outlet on the back of the pivot tube. I can easily blow trough the water jacket on that side as well as both tubes. The only thing that I can think of that would cause the heat would be some excessive friction inside, however everything turned over nicely when going back together.
I am going to run it again with the two lines off of the top of the cylinders so that I can compare the water flow.
Has anyone else run into this issue without an obvious blockage?

[The Boat House]

I wouldn’t assume that because air and water is passing through the cylinder you don’t have some blockage. Taking
off the waterlines, blocking the bottom fittings, filling both cylinders with water, and then comparing the amount of water each cylinder held might be a better indicator.

[adam1961]

Tubs,
I pulled the water lines off and did as you suggested. The cylinders held similar volumes of water in the water jacket. I blew air through them again. When going back and forth, one small flake came out of the cylinder that was getting hot. I may have been enough to block the outlet on my last test run. After re-assembly, the port cylinder is still warmer than the strbord cylinder by 15-20 degrees depending on where you check, but it now runs cool enough that you can hold the cylinder while running.

The only thing left to do is better seal the fuel line fiting at the carb. It has a filter screen in there. I pinched two gaskets to go above and below the screen, but I am still getting a small leak. I am afraid to tighten the large nut too tight and break something. The original gasket seemed to be similar to heavy Kraft paper. I have used the thicked grey fiber type gasket stock.

After this, it will sit until warm weather allows for a lake test.

[lloyd]

Might have a lot of rust in the water jacket of that hot cylinder preventing good water flow and cooling contact to the cylinder. Might have to remove that cylinder from the crankcase to completely clean out the water jacket.

[The Boat House]

• This reply was modified 3 years, 1 month ago by The Boat House.

[stanley]

The screen in the fitting below the carb should fit inside the gasket.It’s cup shaped and fits down inside the fitting,not under the gasket.That fitting is hard to keep from leaking.Make sure mating surfaces are clean and smoothe and use a single gasket.

[sydinnj]

Yes with the screen in the right place and a good gasket and clean mating surfaces I have had no problem with them leaking. I have 3 that have no problem. And yes do not over tighten.

[MICHAEL PEEL-ROELOFS]

I wanted to ask about the muratic acid idea- That works with cast iron cylinders? I’ve used it on aluminium before to remove heavy corrosion but never thought about it’s possibility for iron/steel.

[The Boat House]

• This reply was modified 3 years, 1 month ago by The Boat House.

[adam1961]

Thanks for the info on the screen. This one might have been replaced. I will remove it again and fit it as described.

Adam

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