'57 3hp Johnson operating RPM

[BrayD]

I inherited a JW-13 so I've been tinkering with it trying to bring it back to its former glory. Not sure how long it has sat, but it was in fairly good condition. I changed the plugs, ensured the air intake was clear, threw a new impeller in it, changed the gearbox oil, put some fresh gas in it and fired it up. Starts first pull after it's up to temp and runs smooth as can be.

It's terribly slow though. 3mph on my shallow 14' v hull with only me (140lbs) in it. I put a tach on it to see where it's running. Idles down to 900rpm (take ~1/4 throttle to hold idle) and constant speed at max throttle is 2450rpm. Target rpm for this little guy is 4k. Something's amiss.

Just checked compression today and it's around 80psi on both cylinders. Pretty happy with that. My next thought is it's starved for fuel, so I'm considering a carb rebuild. Just wanted to touch base here to make sure I'm on the right track, or see if there's anything in particular I should do / investigate while I have the carb apart.

Still running the OEM prop for what that's worth. How do I pull some more rpm out of this motor?

 

[airshot]

Idle speed should get down to 600 rpm or in that neighborhood. Had one many years back, would idle down so slow you could almost hear each cylinder fire. I don't know what wot rpm is, but it is much higher than 2450 !!
I would start with a good carb rebuild, you will end up there anyway even if you find another issue. Get a kit ( factory) so you have the new gaskets and needle and seat. No since doing half the job....

 

[BrayD]

Nice. I have a new kit on order and just stripped the carb down last night. No smoking guns that I found. It's currently soaking and I've been periodically scrubbing all of the nooks / crannies / orifices I can find to ensure everything is open and clear.

Good to know it should be running well north of 2450. It seemed to run so well that I almost convinced myself that it's just how this little old motor runs. Looking forward to getting it dialed in and singing again!

 

[lightflyer1]

When I looked it up it said 4000 rpm.

http://boatspecs.iboats.com/Johnson__JW13__3hp__1957/bpe/57e13015

 

[Pappy]

Probably running on one cylinder. They will run pretty good on one.
Pull each plug wire to see.
Pull the flywheel and install new condensers bare minimum. Preferably new coils as well and the old ones are no doubt on their last legs. Clean and set the points at .020. Watch the points arm when setting and make sure you feel the feeler gauge drag but no points arm movement.
What fuel/oil ratio are you running. Should be around a 20:1 mixture and no leaner than 24:1 with the old plain bearings and 3-ring pistons.

 

[BrayD]

Hadn’t thought about that, but it makes perfect sense. Wasn’t seeing much smoke and I’m running 16:1 in it right now.

I pulled the flywheel tonight. Coils and ignition in general looks great. Must’ve been replaced fairly recently. That said, one coil ground wire was rubbing the flywheel and wore the insulation off in one spot. I put some liquid tape on it and moved it away from the flywheel.

Setting the points - if I set it at .020 with the follower at the arrow on the cam, they open far wider as the high point of the lobe is around the ‘O’ location of the ‘TOP’ stamping.

Should I set it at the arrow or the ‘O’?

 

[BrayD]

Follow up - bottom cylinder was dead. I have continuity in the plug wire and had condensors/points on hand. Replaced those parts and still nothing. That only leaves the coil.

Bummer I don’t have a spare coil on hand, but I’m happy I found the culprit.

Edit: checked resistance across the coil and it appeared good. Cut the wire back a bit to get a fresh core and it worked! I’m firing on both cylinders now. Hoping to get it on the water this weekend. I’ll report back. Thanks for the insight.

 

[BrayD]

She runs like a top! Throwing a nice wake and pulling 4k at WOT. Thanks everyone, I feel like I know this motor inside and out now.

 

[Pappy]

Welcome.....glad to know we could help. Now.....about your points. Set them at the o in "top" if you want but, and this is a big one, there is a good chance the new points you have are not as well made as the originals. I would polish the originals and reinstall them and set them properly. Always good to start out with new condensers at the minimum.

 

[mirrocraft16]

I found this article online when working on my '63 3hp,
Johnson J series

I got mine, (a JW18), to idle just over 500 rpm, and it'll max out in the tank at 4150, but on the lake 3,991 is its top rpm.
Mine is a low hours original motor that was handed down to me by a relative who bought it new to use on a duck boat in PA.
It was still in its original box.

 

[BrayD]

I've been reading up on points, how they work, etc. I think I have enough info to be dangerous at this point. Once it was running clean at top RPM, I could hear that cylinder drop out a time or two as I lowered the throttle. Even so, it was idling down around 650 during this outing.

My next step is to replace both plug wires, then start dialing in the location of the max points gap. Once I have reliable spark I think this motor is going to really shine on the lake.

A bit more history on mine: my father in law bought it from his boss over 30 years ago. Ran it on a small boat for a number of years before getting into river fishing. Upsized his boat/motor and this one sat for a while before he gifted it to his brother in law. Same story - he ran it for a while before ultimately letting it sit.

I ended up pulling this 14' V hull out of the woods at our family farm a few weeks ago and my father in law said he had just the motor for me. Enter the JW13. He delivered it with a new Sierra impeller and condenser/points kit still in the package.

Considering how much it has been passed around, I'm sure it's had many hands it in over the years. Super cool to have it running again and pushing another novice fisherman around the lake.

 

[Pappy]

Sierra points are hit and miss.....mostly miss. That is why I said to polish up the original points and reinstall them. Good time to do it will be when you replace plug wires. When you look at the OEM points side by side with the Sierra you will agree. Points alignment alone on the Sierra is pretty bad compared to the OEM.

 

[BrayD]

I hear that, Pappy. I'm just not convinced that the old points are still OEM. I'll look a bit closer when I have it opened up again.

 

[Pappy]

how many years ago were the points looked at or possibly changed?

 

[BrayD]

Hard to say. The motor has been with the previous owner for at least a decade. That's how long I've been with my wife and I've never seen it at my FIL's house.

The Sierra parts came from the previous owner which makes me think they were proactive about maintenance. Coils are different colors so someone has had their hands in it at some point.

Best pic I have from when I had it apart. Shows the wire with the worn insulation and the (one set of) points as I received them.