Military Surplus Johnson 25hp

I just boought a OD green, Military Surplus, extra long shaft 25hp Johnson, Model RDM-14. <br />Some research revealed that it was built in 1953 and used to move barges and combat bridge sections. It's built like a tank with armored spark plugs and wires, etc. The overall construction is heavier than a commercial Johnson, but it is mil-spec. In fact, it weights 140 pounds.<br />I plan to mount this on my Aquarius A-23 sailboat, which can make good use of the extra long shaft.<br />This motor has been stored for decades. I plan on breaking it down partially, cleaning it up and replacing parts like the impellor, points, plugs, carb kit, etc. <br />The prop has a few minor nicks in it and some small bends. It's a 11 x 9, with extra big blades. This would hardly power a speed demon, but it would push a house. As far as repairing the prop, I'm a Master Clockmaker and used to moving metal around and finishing it.<br />My big proplem is, where do I find a shop manual for this vintage Mil Spec motor?<br />In fact, I can't even find a spec sheet or shop manual for a commercial model Johnson 1953 RD-14. I figured 80-90% of the commercial parts will interchange with the Mil-Spec. The armored spark plugs and wires can be replaced with regular ones, etc. I have no intentions of paying $20-25 for NOS armored spark plugs, even if I could find them...Besides newer plugs are much better performing. <br /><br />I still would like to have a shop manual or tech/spec sheet on this motor. I suspect all of the early 1950s Johnson/Evinrude 18-25 hp motors are pretty similiar. I have a 1950's 18hp Evinrude which has a very similiar powerhead. <br />Can anyone point me in the right direction?

Re: Military Surplus Johnson 25hp

dp,<br /><br />I think the manual reference below will be of help. That's a rare unit you have there.<br /><br /> http://www.iboats.com/boatproducts/mallsearch/johnson_outboard_manual/ <br /><br />"MIL" units of that age were super built regular production engines with the nifty protective items you mentioned.<br /><br />With that said, that unit should still run with a 24:1 gas/oil ratio using a good TCW-3 rated outboard oil.<br /><br />Before you get into it too deep, I would rebuild the carburetor/fuel pump and water pump with regular production service kits. They're readily available, here on iboats. I doubt that carb and H2O pump kits are different from regualar production units.

Re: Military Surplus Johnson 25hp

if i were you i would just look on ebay. they usualy have a big range of used outboard books. but i wouldnt bother i have restored and repaired many outboards without a service manual. service manuals are only good for specs like fuel mix breaker point gaps spark gaps and things like that. if your only doing minor teardown like taking cylinder head off and carb and leaf plates its simple. i usualy take a few minutes to look at the part ive taken off and and remember where things go before i tear it apart. this might be a usefull link http://ww3.kencook.com/evinrudejohnsonmanuals/index.cfm?fuseaction=search.search

Re: Military Surplus Johnson 25hp

dp,<br /><br />I agree that Ken Cook is a great source for manuals.<br /><br />However, ignoring ESSENTIAL items such as H2O pump and carburetor will soon turn a classic into a paper weight, albeit; a "serious one".<br /><br />Let me add this.<br /><br />Those engines were really "jewels" of craftmanship. They are capable of outliving ANYTHING on the market today, WITH PROPER CARE. <br /><br />They're not necessarily efficient, or clean, yet they are bulletproof, again, with proper care and maintenance.<br /><br />We'll help you through.

Re: Military Surplus Johnson 25hp

If your A-23 is 23 feet long, that 25hp would be insanely large for it.<br /><br />The prop that was used on that outboard was also used on 28, 30, 33, 35 and 40hp engines up into the 70s. Replacements if you need one are easy to come by. In fact, you can buy one brand new from Iboats if you need to.<br /><br />Those engines share a lot in common with yours. Your 25 was developed in '56 into the 30hp, in '57 that was developed into the larger displacement 35hp and in '60 that was developed into the even larger displacement 40hp which they sold for years afterward. In '62 the 30hp was reincarnated into the 28hp and it got replaced in '65 by the 33hp (a reincarnation of the 35hp).<br /><br />The 15/18hp (22.0 CID) engines had their own parallel run, winding up in the 70's as 20hp and 25hp engines (still at 22.0 CID, but many small changes were made).<br /><br />Spark plugs for the civvy version were Champion J6J (now J6C's) gapped at .030". <br /><br /><br />Neat project! Keep us up-to-date!

Re: Military Surplus Johnson 25hp

Paul,<br /><br />Wow!<br /><br />Was I "off" on the advice?

Re: Military Surplus Johnson 25hp

I once got my hands on one of those engines, and as you say! they are quite unigue. The transom clamps are different than any thing you will see on a regular engine. The shielded ignition can be taken down to bare bones. You can get rid of all the shielding, and end up with a magneto the same as the civilian version, use a j-6-c plug. The gearcase was also heavier with all roller, and ball bearings. I think I still have that 25" drive shaft lying around somewhere. Where the heck did you find that critter? Carb & ignition parts are still available, not sure about the water pump.

Re: Military Surplus Johnson 25hp

Back in the mid to late '60s, the government contracted with OMC to produce those 1953 motors again but this time for VietNam. Quite a few were built on a special production line and shipped overseas back then.<br />Your "1953" model may likely be 1968 built.

Re: Military Surplus Johnson 25hp

Oh, I know the 25 hp is a wee bit overkill....But you have to mind that, unlike a powerboat, I've no intentions of running WOT all day long. The outboard is mostly for manuvering around the dock and for emergencies. For normal manuvering, part throttle is all that is ever needed. <br /><br />Besides, I've heard of horror stories of having too little motor on a sailboat when tides and winds overcomes your headway and smashes sailboats on the rocks. At best, too little motor means you get nowhere fast. I think a 10hp would be the least you would need in a 23 footer; Winds and tides are not always calm or going your way. Hanging a 3-5hp on an A-23 is like pulling out into a fast moving, crowded Interstate with a Pinto. You're better off with sails and prayers.<br />With common sense, the worse can happen with that Johnson is that I get lousy fuel economy... But if I have to MOVE NOW, the 25hp Johnson will allow just that. <br />The main reason I got that motor is that is has an extra long shaft. With your friends up front checking out the forward scenery, if there is any wave action, a short shaft will have the prop out of the water most of the time. If you need to stop or back up, it can be embarrasing, if not downright dangerous, to have a prop turning in the air while you crunch into something.<br />A mil spec motor is realiable if well care for and tuned. The only objection I have is the weight (140lbs).<br />I still want a shop manual. I was raised up in a service station in the fifties and sixties...I've built many a engine for motorcycles and car/trucks in my younger days. I've even worked on some airplane engines (glorified volkwagons), I can even do some top knotch work with an air carbide tool in porting a race head...Yet, the first thing I want to do is get a shop manual. I always like to have my ducks lined up before I break the first nut loose. If nothing else, it saves time trying to figure out how things work, and how they go back togather...Never underestimate the challenge.<br />There are many times novice clockmakers show up on my doorstep with a pile of gears and brass plates...having forgotting just where one little screw or wheel goes. The reason I am a Certified Master Clockmaker (CMC)is because I studied every shop manual on clocks that I could lay my hands on...Until the point where not only did I know just where one little part went, but exactly why that little part went there...and If I needed, I could take a sheet of raw brass and steel rod, and fashion a better one by hand.<br /><br />When the novice came to me with his basket of parts, not only could I reach in and tell him where every part went, but to tell him to go home and search under his work table for that part that wasn't in that basket...because I knew exactly what the maker of that clock was thinking when and how he made it. Everthing has it's place and fuction...And it was my fuction to know what that was.<br /><br />So sincerely, with all do respect, even though an outboard motor is child's play compared to the average grandfather clock movement, I'd rather have a shop manual to be sure I get it right the first time. And when I'm done, I want it to work like...well, you know.<br /><br />Donald A Plisco (CMC) <br /><br />

Originally posted by Paul Moir:<br /> If your A-23 is 23 feet long, that 25hp would be insanely large for it.<br /><br />The prop that was used on that outboard was also used on 28, 30, 33, 35 and 40hp engines up into the 70s. Replacements if you need one are easy to come by. In fact, you can buy one brand new from Iboats if you need to.<br /><br />Those engines share a lot in common with yours. Your 25 was developed in '56 into the 30hp, in '57 that was developed into the larger displacement 35hp and in '60 that was developed into the even larger displacement 40hp which they sold for years afterward. In '62 the 30hp was reincarnated into the 28hp and it got replaced in '65 by the 33hp (a reincarnation of the 35hp).<br /><br />The 15/18hp (22.0 CID) engines had their own parallel run, winding up in the 70's as 20hp and 25hp engines (still at 22.0 CID, but many small changes were made).<br /><br />Spark plugs for the civvy version were Champion J6J (now J6C's) gapped at .030". <br /><br /><br />Neat project! Keep us up-to-date!

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Re: Military Surplus Johnson 25hp

BTW: What's the displacement on this 25hp Johnson?

Re: Military Surplus Johnson 25hp

She's 35.7 cubic inches, or 585cc.<br /> '53 Johnson catalog, click here. <br /><br />(for more specs you'll have to look at the '52 or '54 Evinrude catalog).<br /><br />OMCFreak gave you a URL to where old OMC manuals come from. Although the don't list the RDM-14, they do have the original service manual for the civilian RD-14. You may want to contact KenCook to find out if they do have the master for the RDM-14 anyway and just haven't listed it. Otherwise, try over at AOMCI.org. Someone there might have it.<br /><br />As much as I can applaud you for wanting to fix up this old engine, I still think your intended application is poor. From what I can see, your sailboat wants a 6-9.9hp engine, not a giant 25hp from the 50s. You may need to reinforce the transom and outboard bracket to support it bouncing around back there. For comparison, on my brother's Shark 24 (light & small for a 24' at ~2400 lbs) we use a 4hp and we hit boat speed at around 2/3 throttle. I would agree more would be better for headwinds & tides, but the boat is only rated for 4-6hp according to her designer.<br /><br />Fuel economy is especially poor on these engines when they are operated in the mid-range. Compared to modern engines, they're not so bad at 3/4-full throttle.<br />There's also the fact that in idle you'll be going faster with the larger engine. Which can make docking manuevers a little tricky. But if your good at figuring out when to cut the power and put it in neutral, that won't be so much of a problem.<br /><br />Another thing; these older engine's must be set a little deeper than new ones for their water pumps to work correctly. The only real trouble is in neutral - once in forward water is shoved up the intake by the propeller. The 15" transom engines measured the way a modern outboard is measured check out around 18". Just make sure it pumps water in neutral properly once you have it set.<br /><br /><br />I hope I'm not coming across as too down on the idea! I think it would be really cool to have a 23' with a '53 military Johnson on the back. But there's a reason you rarely see anything over a 9.9hp outboard on a sailboat.<br />I think I've got my brother convinced to paint a shark's mouth and eye on the bow's sides.