What Should I Replace on A 49 Year Old Johnson Motor?

[cigarxtc]

Ok, so I'm going to try to get my motor up and running in time for spring 2004. It's a 1954 Johnson Seahorse, 25hp, RDE-16. It's completely stock. I don't know how long it's been sitting around, but externally it's in great shape. The compression tests good at 110 and 115 psi in the two cylinders. The starter motor works great.<br /><br />Here's what I'm planning to replace:<br />-points<br />-condensor<br />-both coils<br />-both plug wires<br />-impeller<br />-prop shear pin<br /><br />What else should I replace before putting it out on the water?(I'd rather not have to take the power head apart if feasible, but I will take the lower unit apart for inspection and impeller replacement.)

 

[Mark42]

Re: What Should I Replace on A 49 Year Old Johnson Motor?

How about replacing the following items too:<br /><br />- Lower case lube (until you get to pull it apart).<br />- Fuel line/bulb.<br /><br />And also do/check the following:<br />- Check wire harness for rubbing/chafing damage.<br />- Grease all linkage. <br /><br />Mark.

 

[ledgefinder]

Re: What Should I Replace on A 49 Year Old Johnson Motor?

Excellent motor! I concur on the impeller, coils & fuel line. I'd do a decarb. If you have any $ left over, a new prop can make a BIG difference, if the old one's dented and/or wrong pitch for your application.

 

[rolmops]

Re: What Should I Replace on A 49 Year Old Johnson Motor?

hello.<br />I would add the packing in the needle valves on the carburator to your list.<br />As far as the coils are concerned,I would first see if the old ones are cracked and decide accordingly.<br />good luck.

 

[JB]

Re: What Should I Replace on A 49 Year Old Johnson Motor?

Hi, Cigarxtc.<br /><br />Generally I don't believe in fixing something that isn't broke, unless it is a part with a predictable life span and is close to that span.<br /><br />That surely covers your impeller, needle packing, carb gaskets and lubricants.<br /><br />If inspection of coils and plug wires proves them cracked or brittle, change them. Otherwise there is no benefit. Fuel lines, "O" rings in the gas fittings and the primer bulb may also become brittle and useless with age.<br /><br />You can do no harm by changing the condensers and points, but there is a very good chance that you are just wasting time and money there, too. Some condensers dry out with age, but points are unaffected.<br /><br />Good luck.

 

[Chinewalker]

Re: What Should I Replace on A 49 Year Old Johnson Motor?

If you're planning on taking the gearcase apart anyway, I would go ahead and replace all the seals, particularly the shift-rod o-ring. These are items that can harden with time and lose their ability to seal properly.<br /><br />Also, if the condensers are of the type that have a rubber top, then they're likely okay. If they have the original fiber type, then I would change them as a matter of course - Murphy's law states that they will fail when you're down stream of your dock without a paddle...<br /><br />- Scott

 

[cigarxtc]

Re: What Should I Replace on A 49 Year Old Johnson Motor?

Thanks for the feedback, all. The coils are cracked and shot. There's no spark when the engine's cranked. The plug wires are also getting hard. The points and condensors look fine, but I'll replace them and keep them as a spare for when I'm on the lake. I guess I'll be rebuilding the carb too.<br /><br />Does Napa carry all these parts? How do I find part numbers for whatever replacement parts I might need for this motor? Are the plug wires a seperate part number from the coils?

 

[Paul Moir]

Re: What Should I Replace on A 49 Year Old Johnson Motor?

Yup. Those fall into the 'consumable' parts you can get aftermarket copies of from NAPA. They have a Marine parts catalog (Sierra parts).<br />18-5006 - Points and Condensors (includes two of each).<br />18-5181 - Ignition coil. (You'll need to order two.)<br />18-7024 - Carb Kit. (This does not have a float. You can get that from a J/E dealer)<br />18-3006 - Water pump Impeller.<br /><br />You can buy these from many online parts dealers as well. You can also buy the OEM equivalants (the part numbers are different) from a Johnson dealer.<br />I've got a '62 28hp Johnson that I've rebuilt from the ground, which has the same displacement as your 25. It looks exactly the same too.<br /><br />Good luck!

 

[alcan]

Re: What Should I Replace on A 49 Year Old Johnson Motor?

It sounds like everyone has covered the the bases pretty well. The one thing I find most guys tend to miss on these older motors is the fuel tank itself. These older presurized tanks are usually in need of an over haul. As JB mentioned eairlier, Replace the O-rings in fuel line connector (buy some spares also). I feel these o-rings are the weekest link in the whole show. I get more guys thinking their motor is shot and it is due to 50 year old o-rings or a leaking gas cap rubber. Another little problem related to the tank is the primer pump plunger button. This is the model with the aluminium plunger (later models had a plastic botton). The knob on the shaft needs to be free to rotate separate from the shaft. This joint has a tendency to freeze up. When you pump the primer with your thumb, your thumb tends to torque this knob. If the knob is stuck to the shaft, it will apply torque to the diaphram inside. This either causes the diaphram to tear or the nut on the end of the shaft to come loose, resulting in a leak. A lot of guys do not care for this presurized system. I believe this is mostly because they don't fully understand it, and do not fully repair it. Remember were talking about fifty year old equiptment here. If repaired properly it may be depenable for another fifty years. These 25hps are one of my favorate motors. I own several they all run and I use them as much as I can.

 

[Chinewalker]

Re: What Should I Replace on A 49 Year Old Johnson Motor?

Good points Alcan! I'm always puzzled by folks who try to jump ship from the 2-hose tanks right off the bat. Old dual-line tanks are available at swap meets and on eBay all the time, generally for less than it would cost to buy a new plastic tank, fuel pump and related plumbing.<br />Check out: Vintage Outboard Supply for rebuild kits.<br />- Scott