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79 johnson 25hp what else to check before taking it out

T

Tom Soltes

New member
I am new to motor boating and recently found what I thought and still do think was a good deal on a 79 25hp Johnson. At first I had some difficulty getting it started but with a neighbors help was able to do that. It didn't seem to have as much power as I thought it would and it didn't seem like the throttle control moved very far. I found a stop screw on the cable leading to the carburetor, removed that and that took care of that issue. My guess is that it was used on a small jon boat and the stop screw was used to limit the power of the engine. Next issue was the water pump. When I first got it started I wasn't getting water out of the "pee" holes. I used a jet stream water hose to flush both ends (intake and exhaust) of the water outlets and started her up and it was working. Next is I got a lot of smoke out of the engine but my neighbor said that wasn't anything to worry about. Now with all of the above I really did not have it running that long and all seems to be okay. This was all done on a stand with the engine in a barrel of water. One last thing I wanted to do before taking it out was change the gear lube. I checked with an online manual and learned that process. Got new gaskets for the vent and fill then opened up the vent then drain. What came out looked to me to be clear water. I had it drain into a tub that I had used for an oil and gear change on my moped so it already contained residue from that. Not much came out but it certainly appears to be clear water. I started to pump in gear fluid and then after several minutes of doing this I noticed the gear lube dripping from the other side of the motor. I checked and found it coming from a missing bolt hole that connects the propeller housing to the lower unit. I checked all six of the bolts and three were missing. Ran out to the store and picked up stainless steel bolts and put them in to all the missing holes. One was missing on the vent and drain side of the engine and two on the opposite side. I then completed the gear lube process as described in the manual. That was all completed yesterday and none of the gear fluid has leaked. What should I do next on land before taking her out ? I would like to get some suggestions on anything else I should look for before taking it out and also any thoughts or ideas on why it had only water in the gear case. What precautions should I take before going into the water and when I do what should I be looking for to tell me that trouble is ahead. Thanks
 
I would change the impeller before running it too hard. They should be changed about every two years. They sit in a cup with the rubber fins bent back pretty far, eventually the rubber hardens and looses it spring and the rubber fins are permanently bent back. It only pumps a little water at high rpms when this happens. Never run it out of the water either. It will overheat and also burn up the impeller in a few seconds because there is not water to lubricate and cool the impeller. After you run it on the water the first time for a while and get it back to the house, drain the lower unit again and see if there is any water in it. Look for rust, metal shavings and water. If there is, you will for sure need to rebuild or replace the lower unit. Hope that helps. If all is well, enjoy the motor for years to come. They are great motors.
 
i would also check your fuel lines for dry rot and if so replace because you dont want to end up having to rebuild the carbs because of small rubber pieces from the house clogging the carb if they are working fine now and also try and find none ethanol gas older motors seem to run better on ethanol free gas
 
All above are good and proper suggestions. All outboard motors run better on non-ethanol fuel! If at all possible, try to use non-ethanol exclusively. If that is not possible, always use a good stabilizer like Sta-Bil Marine or Startron.

There are some really knowledgeable folks on the Johnson/Evinrude forum on this site. Go to "Forum Home" at the top of this page, and pick the Johnson/Evinrude forum and post your questions there also. Bubba is right, these old Johnson 25's were built to be workhorses and are rugged old engines. Keep them on clean, fresh fuel, change the plugs and impeller every season, and make sure you keep the proper fuel oil mixture running through them, using a high grade two-stroke oil, and they will run forever. The more often you can run that engine, the better it will run. The only thing I would add to the above is to pull the thermostat and test it or replace it. If that engine runs too cold, it will smoke a lot and carbon up quickly.

Once you are up and running, decarbonize the engine. That will both clean your carbs and clean out hard carbon deposits on the pistons and valves, and will generally improve performance. The preferred decarbonizer around here is Sea Foam. Use a small tank that you can hook up to the fuel inlet on your motor. Run through a mixture of SeaFoam to gas in the 3:1 mixture. You only need about a half gallon at most. Once the mixture is injested well, shut off engine. Let it sit for 15 to 20 minutes. Restart. Don't be surprised to see all kinds of black junk and white smoke coming out of the exhausts. Repeat the process one or two more times. I've seen this decarbonization procedure revive old two-strokes that looked like they were on their last legs. After that, make it a habit to throw in a can of SeaFoam in your fuel tank about every second or third fill up IAW the instructions on the can. This stuff works well in all kinds of small two-stroke and four-stroke engines.

Good luck, and let us know how it tests out on the water.
 
a good brand of two stroke oil would be amsoil johnson manufacturer recommends the johnson 50:1 lubricant johnson also says if you cant find this that any BIA,TC-W or TC-2 certified lubricant my be used but i have always used the amsoil for all of my 2-strokes and it works wonderfully burns clean and does not leave carbon build up and i personally love the smell it gives off it just smells like it is burning clean and i have never had any problems with build up on any power valves, reeds, pistons or cylinder heads
 
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