TOPIC: 1973 Johnson 115 Major Tune Up!

Recently purchased, been sitting up for a few years. Just wanted to get organized into one thread for ease of reference. Only previous experience on anything of this size was on Merc700FGS, so this is all new to me. Had the wrong spark plugs installed, got the new proper ones ready to go in when we get to that point
The compression check was good, 'bout 149 on all four holes!
Spark check good, nice blue flame across each plug - so far so good.
Getting ready to refresh carbs and fuel pump, pics for reference on linkage, hoses, etc.
Did I mention someone used black "form-a-gasket" on carb to silencer and carb to intake mounting? NEVER a good idea folks!
Fuel pump is newer high output model according to the shop manual, really doesn't appear to need the kit!?
Enough for tonite, still kinda weak and sore from recent surgery.

Looks good. What you gonna put it on?

Thanks, Dave. It came on the 73 Glastron V178 Starflite I bought a couple weeks ago. The whole thing is in pretty good shape, or so it appears. I needed something to get out on the water with while re-doing my 58 Cutter Tornado with a 62 Merc 700 FGS.

Anybody have an exploded view/diagram of the 438559 fuel pump? I was kinda tired when I put it back together, wanna make sure I got it right! My biggest question is the placement of the small oring
Also just noticed the green gasket that goes between the pump and the silencer wasn't on there when I took it apart! And he wondered why it wouldn't idle. Guess I'll have to break that kit open after all.

I too have a 62 Merc 700 FGS

Very nice, wish the paint on mine looked that good. I've enjoyed working on the Merc, but this Johnson is like starting all over again with the "learning curve". It does seem to be a little easier to work on, but then it's not as old and a few less cylinders. (At least you don't have to pull so much stuff to get the carbs off!)

Pulled the carbs off today, black rtv silicone everywhere! What a mess. It was down in the float bowl too, so this is definitely a BAD IDEA to anyone thinking about using this stuff on carbs or fuel pumps.

I need some advise/guidance on how to safely remove the "welch plugs" you'll see in the last pic below. I really need to clean out all the bad gas and chunks of silicone. I have blasted carb cleaner through all the holes and orfices, but something tells me to pull these plugs for inspection, if nothing else. The carb kits contain new ones, I just don't want to bugger up the carb housing getting them out!

Simple ---take a 3/16" drill bit. Put some tape on it so you will only just drill thru the plug.

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Pry them out.

Thanks, Adrian, I'll give it a go. After cleaning, just put the new ones in place, put a socket (or something flat) on it, and whack it with a hammer to flatten it out , right?

Have a peek at this video Mark...might help.

It sure did help, thank you my friend! That was almost as good as having someone come over and show you how to do it. I'm going back out in the garage and finish up the carbs this morning, was starting to get a little sore and tired last night. Like Frank says, I'm learning to listen to my body when it tells me to quit for a while.

Well, I finally got the carbs & fuel pump rebuilt (with a little help from my friends, Thank You!), and reinstalled. So I took her out into the driveway today for a test fire, sounded pretty good. Actually, it was popping and belching a little, then I remembered unhooking the bottom carb choke linkage to install the choke solenoid. Opps. Yeah, it was closed completely. Once I got that straightened out, she smoothed right out.

I've gotta read the instructions on my digital camera, think it might take short videos. Time for the old dog to learn another new trick!?

There was very little water coming out the tell-tale holes, so I shut it off after a couple minutes and rolled it back into the garage for a water pump kit install next weekend. Now that I think about it, I'd better read the manual to see if this motor has a thermostat. It didn't run long enough to get hot, but that may explain the low water output. Gonna do the pump kit anyway, it's gotta be a good idea since I know it's been at least three years since it's had one.

While we're on the subject of cooling, does anybody know where I would hook up a water pressure gauge on this engine? As always, any help would be greatly appreciated.

Stay tuned, film at eleven. Just not tonight.

There's a video for that too Just in case it helps.

Thanks, Chris!

Most/ allof the bigger OMC outboards have had a thermostat/s since 1960's

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Spitting out those two exhaust relief is normal.

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Temperature gauge kit is available as well.

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If you do not know the condition of the impeller , replace it.

Thanks for the input, Adrian. I'm definitely going to install the new impeller, already have the kit. (Just have to wait on my hernia surgery to heal another week before I tackle that project.) I plan on installing a water pressure gauge soon, just don't have the funds right now to procure the parts.

Update - Found a 30psi water pressure gauge for a super reasonable price, still need to know where to "hook it in" on the motor!

Decided to pull the lower unit today to install the water pump kit, and hit a snag right off the bat! The manual said to simply pull a snap pin to disconnect the shift linkage, but there wasn't one in sight anywhere. I could see the shift rod sticking up under the bottom carb, but it appeared to have a drift pin holding the rod to the bellcrank. NOT wanting to pull the carbs again, I disconnected and removed the control cables from the starboard side of the motor to get a better look. The front side of the pin is still Johnson green, and the back side is right up against the intake manifold. After studying the BRP site parts breakdown, I figured out that the pin is pressed/welded into the front half of the two piece bellcrank. After taking out the center bolt and separating the front half, the pin came off with it and the shift rod was disconnected! The rest of the job was pretty mundane, will reassemble tomorrow.

Also found a water passage cover on top of the engine where the v of the cylinders comes together that appears to have provisions for drilling and tapping in a water pressure gauge line! It's been a good day.

Sounds like you have had success. Good to hear.

Thanks, Chris, I'm pretty well pleased with the progress. Hoping for a shakedown cruise next weekend if all goes well.

Tune up and water pump kit complete, ready for test run at the lake tomorrow. AMAZED that the lower unit on this holds a full quart, the Merc 700 only took a pint. Mo lube mo better, right!?