1953-1967 Evinrude Johnson 3HP Tune UP Project Water Circulation

Up to this point, I have not pulled the cylinder head because the motor would turn over and seemed to have good compression.  With the motor overheating, it was obvious that I would have to dig deeper to find out why water was not circulating through the power head.  I knew the impeller was working because I did have water spraying out of the lower unit.  I also pulled the flush port screw and could see that water was sputtering out from there.  Something was plugging up the water passageway in the power head and not allowing water to circulate around the cylinders.

Removing the Cylinder Head - Remove the side covers to expose the cylinder head and spark plugs.  There is no need to remove the gas tank for this procedure.  Using a 7/16 socket wrench, unscrew the 6 bolts holding the cylinder head on.  You may need to use a knife to break the head gasket seal.

Lightwin Cylinder Head Clogged
Cylinder Head Clogged


Lightwin Removing Crud from Cylinder Head
Removing Crud from Cylinder Head


Lightwin Cylinder Head Ready to be Installed
Cleaned Up Cylinder Head


Once the cylinder head was pulled, I could see that crud all around the inside water passageways completely blocking any chance for water to circulate and cool the cylinder head and cylinder walls.  These passageways were completely dry even the motor was run only 15 minutes before removing the cylinder head.  Not knowing the history of this motor, I can only imagine that it must have had an overheating problem for quite some time because all the water passageways were completely clogged with what appeared to be calcium or possibly mud or silt.  It almost looked like the motor was used to mix concrete!  The original owner of this motor is deceased and the guy I got this motor from never really used it and let it sit in his garage for years.  Unfortunately, I think most motors in this condition would wind up in a dumpster somewhere but with nothing to loose, I started cleaning out the passageways to see if I could get the water circulating again.

Remove the Lower Unit from the Power Head - The power head is held onto the lower unit with only 5 straight head screws.  Remove the 5 screws and lift the power head off the lower unit and drive shaft.  You may or may not be able to do this without destroying the gasket.  Now you have access to the bottom of the power head where water is pumped up through the tube and returned, along with the exhaust through the lower unit.

Remove the Air Silencer and Exhaust Cover - The exhaust cover is held in place by 6 screws, one of which also holds the air silencer in place.  Remove the air silencer screw which is longer than the other 5 screws and the air silencer.  Once the air silencer is removed, the exhaust cover can be removed by removing 5 remaining screws are removed.  Again, there is a gasket which may or may not be removed without being destroyed.  Do not worry if these gaskets are damaged or destroyed.  When I reassembled, I simply used a thin film of silicone on each of the mating parts.

Follow the Water Path and Remove All Blockages - At this point, you can start following the path of the water as it is pumped up through the water pump tube, into the cylinder walls, and around the cylinder head, and back around to the exhaust port. Some of these passageways are quite small because Evinrude did not want these motors to run too cool. There is no thermostat to regulate the flow of water through the cooling system. I used a wide assortment of brushes, wires, and even small drill bits to get these passageways cleared. A small Dremel Roto Tool with a small wire brush came in handy to get all the crud out of the passageways. I also used my air compressor to blow out all passageways and help follow the path of the water. With the cylinder head, exhaust cover, and lower unit removed, I was able to trace the entire path of the water as it circulates through the power head. It was quite challenging figuring out where that water was going to go next. Sometimes I could not see the hole for a passageway until I did some cleaning and even then I had to probe around with a pointed object. I finally reached a point where the water reached the outside cylinder walls of the bottom cylinder with no place to go. At the bottom of the lower cylinder, I resorted to drilling a horizontal hole to connect the cylinder wall passageway to where the exhaust and water get dumped into the lower unit. When drilling this hole, it did not feel like I was drilling through 1/8 inch of aluminum, but rather I was simply unplugging an existing and completely hidden hole that all the water had to return through. I used a 1/16 inch drill bit to clear this hole.

Install the Exhaust Cover and Air Silencer - When I removed the exhaust cover, the gasket was destroyed. Since this gasket does not hold back a lot of heat and pressure, I was able to get by with spreading a thin layer of clear silicone onto both mating surfaces. I am told that this is not an uncommon practice and actually works well. Silicone sealer was not around when these motors were built so thin paper gaskets were used. When replacing the screws, be sure not to over tighten.

Attach the Lower Unit to the Power Head - When I took these apart, I destroyed the paper gasket. When putting back together, I used silicone as described above. Do not over tighten the 5 screws that hold the lower unit onto the power head. I tightened mine just about a quarter turn past snug. Again, this is not a high-pressure or high-temperature seal. It simply keeps water from leaking from between the two mating surfaces. Silicone works amazingly well when used this way.

Clean, Level, and Install the Cylinder Head - Using my Dremel Roto Tool and wire brush, I cleaned all the carbon deposits from the piston and cylinder head. Do not get carried away with the wire brush because cleaning to the bare metal can cause hot spots on the piston or head which will cause problems.

Cleaned up Cylinder Head
Cleaned Up Cylinder Head


Lightwin Sanding Cylinder Head Flat
Sanding Cylinder Head Flat


These cylinder heads usually become warped over time because of the heating and cooling of the motor.  Since I do not have a milling machine, I simply place a sheet of fine grit sandpaper on a piece of glass or something flat and move the cylinder head in a circular pattern until the mating surface is flat.  You can tell when the surface is flat because you will have shiny bare metal all the way around the surface of the cylinder head. 

18-3841 Head Gasket for 3 HP Lightwin

Head Gasket   OMC Part Number 203130    NAPA/Sierra Part Number 18-3841

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This is one place where I did use a new gasket.  Lubricate the gasket with 2 cycle oil and bolt the cylinder head back onto the motor block.  The holes on the cylinder head are not symmetrical so that the head will not go back on the wrong way.  You may need to rotate the head 180 degrees if the bolts do not seem to line up.  Be sure not to over tighten the bolts.  Everyone seems to think that head bolts need to be really tight.  This will only warp the head.  Again, only tighten a quarter turn past snug.  When you tighten these bolts, you need to snug down every other bolt until you have them all snug and then go back around skipping every other bolt until you have them all tightened a quarter turn past snug.  This way the head will be evenly attached to the block.

Now that the cylinder head is back on, you are ready to test the motor in the barrel.  When I tested the motor, it did not run hot. I was actually able to hold my hand to the engine block while the motor was running and the temperature was not hot enough to burn me.


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