How to Tune Up an Older Small Motor

7/31/2019 How to Tune Up an Older Small Motor

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HOW TO TUNE UP AN OLDER SMALL MOTOR.

DO you have an older small Evinrude or Johnson outboard from 3 thru 25 HP that needs a little help? orperhaps you would like to get a good small motor without spending from $1300 up for a new model?

Then you have come to the right place. We will go through the complete procedure to do a major tune up on asmall motor, in this case a 1962 Evinrude 3 HP I was lucky enough to win in an E-bay auction. The seller said itdidn't run but I could see from the images provided that it was in pretty good condition. Turned out to be almost

unused!

This particular model was built essentially unchanged from 1951 through 1967 and as a 4 HP up into the 90's.You couldn't ask for a better trolling motor. Where do YOU get one? E-bay and other auction sites have motorsup for sale all the time. Yard sales, flea markets, even your local dealer may be happy to sell you an older motorthey don't think is worth repairing. Use good judgment, don't buy a motor that is worn out! Generally the nicerlooking ones are in good shape.

These are the components we will be using to get this little jewel into perfect condition. All these parts will costyou just a little over $125.00. The entire project should only take you a Sunday afternoon, and will reward youwith a motor that runs better than new.

Most of the small pictures are active links to full size photos to help you along. Just click to look, they will openin a new browser window.

To begin you will need ordinary QUALITY hand tools, a feeler gauge, flywheel puller, torque wrench, someOMC Engine Tuner or Mercury Engine Cleaner, a gallon or so of cleaning solvent or paint thinner, moly lube,silicone dielectric grease, a CLEAN workbench. All the parts as well as the entire motor should be rinsed cleanwith the solvent, cleanliness is imperative. An otherwise good job will be ruined by grunge. Be sure to work ina well-ventilated area and keep your hands as free from cleaners as practicable.

The first area we will approach is the ignition system. OMC used a "Universal" magneto on most all small

outboards from the early 50's right on up to just a few years ago. Over time the components on the earliermodels will deteriorate requiring replacement. Fortunately these components are very inexpensive.


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This image shows the proper type of flywheel puller you need to remove the flywheel. This can berented form your local tool rental as a "steering wheel" puller. DO NOT try to use any kind of puller on theouter diameter of the flywheel as it will bend and destroy it.Pictured is the stator plate removed from the powerhead, on the bench. Simply unhook any advance linkages,unscrew 4 Phillips head screws closest to the center of the plate and lift it off. As you can see in this picture the

original ignition coils on this motor have deteriorated and cracked insulation rendering them useless. You


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should replace these even if they look OK as the newer ones we sell are far superior to OEM.


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CLOSE UP OF THE CRANKCASE HEAD SHOWING BREAKER CAM and SUPPORT PLATE

Thepowerhead with the magneto removed. Clean the breaker point cam and the crankshaft taper with acetone orlacquer thinner to remove all traces of oil. The crankcase head and the stator plate support should be re-lubricated with molybdenum lubricant to help keep the plate from rattling around as well as providing a goodground. IF this area is full of grunge take it apart and clean and regrease. Use locktite on the screws.


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Showing installation of the new coils. Lubricate the ends of the coil wires with some silicone grease like thatused on new high energy ignitions, install the small rubber boots and "roll" the coil onto the wire, making sure itslips in and makes good contact with the pin in the coil. Align the coil heels with the machined surfaces on thestator plate. This is VERY IMPORTANT as error here could cause the flywheel to strike the coil heels, ruiningthe entire magneto. Be sure to install the cam wick under the coil on the irregularly shaped boss. This lubes thebreaker point arms, without it they will rapidly wear away.To set the points, move the cam until the point arm follower is touching the cam at the "TOP" embossedthereon. Set them at .020 with a feeler gauge cleaned of all oil with denatured alcohol, acetone or lacquerthinner. The feeler gauge should slip out from between the point faces with a light resistance and the arm shouldnot appear to move when the gauge is removed. Care taken to set the points exactly the same will result in astrong spark and a smooth running engine.


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I have found the use of OMC Engine Tuner willclean the carburetor without exposing you to caustics, has no unpleasant odor and it rinses away with water.Similar products are available from other manufacturers. Just put the carburetor in an old pan or suitablecontainer and immerse for a short time to remove all the deposits and rinse with water, blow out withcompressed air.The carburetor should be upgraded with a kit even if it is clean. Today's gasoline additives will destroy the corkfloat, rubber float valve tip, bowl gasket and center standpipe seal in a short time. If your motor has rubber fuellines and a fuel pump these should be replaced with modern components as well. Disassemble as far as

practicable. If the center standpipe won't come out that's cool. Just be sure to blow it clear.


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CARBURETOR DISASSEMBLED, OLD PARTS IN REAR.


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CALIBRATION POCKET LOCATION The pen points to the low speed fuel calibration pocket. This areais where the fuel and air mixture is controlled by the needle valve. Small holes are drilled into the carburetorventure under here. I recommend you remove this soft plug by using a small punch or screwdriver to puncturethru the soft aluminum and twist to remove. Blow it out to remove any crud that may have accumulated. Areplacement plug is in the carb kit. Install it in the cavity convex side up and tap it in the center to flatten andseal securely in the hole.A proper float adjustment is critical to good performance. You must bend the metal float tang (do not pressdown on the float valve) until the float is parallel with the body casting as shown here. All older OMC carb floalevels are set in similar fashion.


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PROPER FLOAT LEVEL ADJUSTMENT


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COMPLETED CARBURETOR Here the carburetor is all ready to replace on the motor. Be sure to installthe seal on the center standpipe in the middle of the carb body. Tighten the bowl attach screws evenly and snug.The bowl gasket is thick and if you get carried away you could break the bowl. Basic adjustments for just aboutall older John-Rudes is 1 1/2 turns off seat for the low and 3/4 for the high speed needle valves.


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After a thorough cleaning of the entire exterior to remove 40 years of accumulated dust and dirt, the carburetorwas reinstalled on the motor. The next item on the agenda is the head gasket. All older motors should have thisreplaced for a couple of reasons. First is the materials that the older gaskets are made of is inferior to the newer.Second, you need to examine the cylinders and clean out the carbon accumulation from the combustionchamber and exhaust ports. While the head is off, clean out any scale and debris in the water jacket as well asthe carbon from the piston tops and the head. Use a soft brass brush or a putty knife with the corner rounded off

Avoid scratching the pistons.


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The cylinder head on most of these little engines gets warped and needs to be surfaced. In order to get the headflat, take a sheet of 80 grit wet or dry sandpaper and place it on a flat surface. A piece of plate glass or a plasticcutting board are good choices. Using a little water and a figure 8 pattern work the head on the paper until it isshowing clean metal all across the face. Just so it touches, you don't have to grind out every little flaw. Do thesame to the block face with a mill file to get any residual gasket material off and a good mating surface.

BEFORE : AFTER:

HEAD AND PISTONS BEFORE CLEANING


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AFTER CLEANINGTORQUING THE HEAD BOLTS IS IMPORTANT Reinstall the head to the motor. I use OMC gasketsealing compound on all the bolts and around the water jacket to help seal the cooling system. DO NOT put iton the area where the gasket seals to the cylinders. New head gaskets are treated with a thermal sealer and need

no additional compounds. DO NOT use spray gasket sealers, Permatex, etc. on this surface. It is also importantto properly torque these bolts, starting from the center out in a circular pattern. Do tighten the bolts in severalstages to the proper torque for the motor you are working on.


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WATER PUMP DISASSEMBLEDThe gearcase on this small motor is attached with only 4 bolts and should drop right off. I found even thoughthis motor has little running time several problems in the water pump area. In the picture of the pump

components on the bench, the small ring by the old impeller is some plastic melted through the plate and stuckto the drive shaft. You should NEVER run your motor out of the water as severe damage can occur to the pumpin just seconds on larger motors. Here the damage was minimal and I replaced this plastic hubbed impeller witha brass hubbed one from my stock. This was also missing the small rubber O ring that is used at the top to sealthe splined area where the shaft fits into the crank. Without this it would get rusty and soon wear out.

Clean the area where the stainless base plate is situated on the gearcase thoroughly to remove any old sealer,corrosion, or debris in the water intake area. Chase the threads where the housing attaches with a tap to cleanout any corrosion. Examine the inside of the housing for wear, these wear the most in the center around thedriveshaft and will suck air here and run hot at idle. Lightly face off the housing to remove any burrs, even ifyou are installing a new one. Of course this is unnecessary if you are working with a larger motor and a plastic


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pump with a stainless liner. Be sure to apply some molybdenum grease to the spline above the O ring. Withoutthis the spline will wear out rapidly. Avoid excess and don't put any on the flat top of the driveshaft.


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How to Tune Up an Older Small Motor