1971 25 HP Johnson 25R71 after tune-up

[cocotower]

http://www.youtube.com/watch?v=HgHBTvbRfYE

The motor was already a little warm. Can someone listen to it and tell me if if it sounds "normal" for an old 71 that just had all the ignition parts replaced?

I also cleaned the starter and I still hear the loud clank before each crank. If she's hard to start, as she was prior to my last points gap set, the clanking sounds like a jack hammer to my neighbor. That's with the hood off. With it on, it's a little quieter.

 

[kfa4303]

Re: 1971 25 HP Johnson 25R71 after tune-up

HI coco. That sounds about right. The idle is a little high (twist throttle down. back idel set screw out to allow throttle to turn to a lower position, if need be), but I didn't hear the bang that you mentinoed. Does it sound more like a backfire, or a metal to metal clang? Are you starting it in neutral? Perhaps it's in gear when you start by accident. You may also have some loose paws on the underside of the recoil starter. Those things can make a lot of noise sometimes. What fuel/oil mix are you running? 50:1 is ok, but I run 24:1 in my '66 just to be safe. It should start in one-two clean pulls with no bang or major fuss.

 

[cocotower]

Idle

Idle

http://www.youtube.com/watch?v=gTKCMVk66N0&feature=youtu.be

Here she is idling about as low as I could get her. I haven't even checked to see if she's running on both cylinders since I only replaced one coil, as the other one looked great. However, both condensers and points were replaced and gap set the best I could.

How does she sound? That's in neutral, btw.

 

[cocotower]

Re: 1971 25 HP Johnson 25R71 after tune-up

The clank is perhaps the starter gear hitting the flywheel. I see no other way for two gears to suddenly mesh real quick unless one bangs against the other one until it slips into gear since they are not synchronized beforehand.

The clank is there in the first video I posted but the cover is on and the camera was at the front of the boat so it's not that audible. It's probably just a 1971 "feature" I'll have to learn to live with. heheheh.

 

[kfa4303]

Re: Idle

Re: Idle

That's pretty good. As long as you can shift into/out of gear ok, you should be fine. I would try to get the leg a couple more inches sumberged in the tank, if possible, but otherwise I think you're good to go.

 

[cocotower]

Re: Idle

Re: Idle

I'm starting in neutral. I only put her in gear when I want to see water fly from the trash can faster.

Is that the idle set screw on the throttle linkage next to the carb? It's a tiny flathead adjustable screw?

The throttle hand lever is maybe at 10% and I was tapping it with my hand a little at a time until I found that sweet spot. I would rather have it idle that way when the lever is all the way back.

 

[AlTn]

Re: Idle

Re: Idle

the idle set is on the tiller handle side of the motor, lower pan, below the vertical shaft that connects to the armature plate..you'll see it..it adjust the stop for the throttle...starter motor engagement is a clunk ...make certain the screws holding the starter bracket are tight as this will add to the noise....I had a broken/stripped lower screw and had to go with a bolt and nut

 

[cocotower]

Re: Idle

Re: Idle

the idle set is on the tiller handle side of the motor, lower pan, below the vertical shaft that connects to the armature plate..you'll see it..it adjust the stop for the throttle...starter motor engagement is a clunk ...make certain the screws holding the starter bracket are tight as this will add to the noise....I had a broken/stripped lower screw and had to go with a bolt and nut

The lower mounting hole for the starter is halfway broken off the engine block. Imagine a washer cut in half. There's enough surface to still hold the starter down tight but I need to try to extend that mounting arm by maybe drilling another hold farther up and bolting another arm to the broken one. Again, it's tightly mounted now but worrisome.

 

[cocotower]

Re: 1971 25 HP Johnson 25R71 after tune-up

I am also baffled at why the richness knob on the front of the carb turns so freely and I don't see it connected to anything on the back side.

Also where is the float needle? I can't find any documentation in my multi-model Johnson manual which omits a lot of 1971 25 hp specs but talks aplenty about the other models (a $40 manual at the marine store). On the front it says my model is covered. Yea.

I can smell fuel a lot of times when trying to crank the motor. When I remove the motor cover the vapor is strong. I have seen the carb butterfly valve pretty wet most of the times. Float valve should be something I try first? Where is it?

 

[kfa4303]

Re: Idle

Re: Idle

Yeah I would try to fix the mounting screw for sure. Maybe a pic would help. Speaking of pics, here's one of the idle set screw we're talkling about. They're usually made out of nylon and can fall apart over time, but you should be able to twist it in to advance the timing and raise rpms and/or back it out to retard the timing and lower the rpms. Twisting the screw out will also allow you to physically twist the throttle grip down to a lower position. The trick to dialing in a nice idle is finding a balance between the lo speed idle screw on the carb and the set screw in the pic below. It just takes trial and error. You'll probably need to tweak it one last time oince you're on the water and the motor has more/sufficient back pressure.

 

[AlTn]

Re: Idle

Re: Idle

the richness knob is mounted to an idler shaft, for lack of a better description, and is connected to the idle mixture needle by a rod and crank held to the idle mixture needle by a plastic piece that snaps over the splines of this needle...in operation, it gives you about 1/2 turn in or out on the mixture adjustment, so you need to get the mixture adjusted pretty close before snapping it on.
With the choke on you can expect the choke plate to be wet.
Float needle is inside the carb itself and as well as yours is running now I don't think I'd fool with it.

 

[cocotower]

Re: Idle

Re: Idle

I guess I should mention that my 25R71 is electric. I don't know if the 71's were converted and that in 72 the real ones came out but mine has the starter, solenoid, choke solenoid bracket, etc.

I've posted quite a few topics since I picked up this used boat/motor which needed some TLC to get her worthy of putting on the lake.

I'm now proud to show this little clip of the 71 Johnson on the lake after a tune up kit was installed and gaps were set, new coils/points/condensers/plugs, carb was adjusted and so forth. For now... she runs well and idles so low you can almost count the flywheel revolutions. I found out that tuning the carb needle on the lake gave better results than using a water bucket.

http://www.youtube.com/watch?v=WmFEsn60oDs

 

[AlTn]

Re: Idle

Re: Idle

thanks for posting the video..looks like the 1ST. Mate was enjoying himself...coco, I dunno, maybe it's just me, but I think you may be running on 1 cylinder or the motor is sitting too low in the water. It sounded to me like you weren't getting up to 3,000 rpm.
Did it seem like the motor was getting to 5,000 rpm?..maybe you didn't want to go more than 3,000 with the 1st mate at the helm?

 

[kfa4303]

Re: Idle

Re: Idle

I agree with AlTn. It seems like you're only getting about 1/2 the speed/rpms you should be getting. That motor should be pushing you guys along, on plane, nicely at near or over 20 mph. I would try a few things. The first would be to raise the motor on the transom, if possible. The motors of this era had sort of an odd shaft length. At around 18", they were longer than a standard "short shaft motor" with a leg of about 15", but shorter than long shaft motors with a leg of about 20". As a result, these motors, can often benefit by being raised up on the transom until the anti-vent plate is level, or slightly higher than the bottom of the boat (see pic). I raised my '66 20hp about 1 1/2" and it made a noticeable difference in top end and my ability to get on plane. These old motors can start and idle surprisingly well on only one cylinder too, so you may want to double check the ignition (perhaps a loose s'plug wire?). Here are some vids of guys running very similar set ups to your own so you can compare them to your own motor. Notice how much higher pitched then get at WOT, indicating the proper rpm range of around 4500 rpm. Give these a look-see and report back. You're almost there!




http://www.youtube.com/watch?v=BWEUrfp61OI

http://www.youtube.com/watch?v=teYIoPOR3h4&feature=related

http://www.youtube.com/watch?v=Clz-1FjsZ64&feature=related

 

[cocotower]

Re: Idle

Re: Idle

thanks for posting the video..looks like the 1ST. Mate was enjoying himself...coco, I dunno, maybe it's just me, but I think you may be running on 1 cylinder or the motor is sitting too low in the water. It sounded to me like you weren't getting up to 3,000 rpm.
Did it seem like the motor was getting to 5,000 rpm?..maybe you didn't want to go more than 3,000 with the 1st mate at the helm?

That was half throttle. Notice the lever is straight up. I have done the 1 cylinder test many times by only using one plug... I'm running on both, no doubt. I just have it set to idle very low so I can troll out beyond no-wake should my trolling motor prop fall off again. Don't ask!

 

[cocotower]

Re: Idle

Re: Idle

http://www.youtube.com/watch?v=s8RUBrewuMM

She was flying in this video... you can't tell because she doesn't sound like a dynamite going off on each fire like some other motors I've seen posted. She's fairly quiet. If I had to guess we were going 25 in this video... I *think* I had it at full throttle. With the water choppy I didn't want to go more than that with my little boy in the back. But I think it was full based on the way the linkage is set and all, I'm satisfied for now.

 

[cocotower]

Re: Idle

Re: Idle

I'm pretty sure I was going almost as fast as the second video.. the 68 Johnson. My son didn't turn the camera around to see the trail. Next time we'll get some more shots to help see if she's at max or not.

Thanks, guys.

 

[cocotower]

Re: 1971 25 HP Johnson 25R71 after tune-up

I am also baffled at why the richness knob on the front of the carb turns so freely and I don't see it connected to anything on the back side.

Also where is the float needle? I can't find any documentation in my multi-model Johnson manual which omits a lot of 1971 25 hp specs but talks aplenty about the other models (a $40 manual at the marine store). On the front it says my model is covered. Yea.

I can smell fuel a lot of times when trying to crank the motor. When I remove the motor cover the vapor is strong. I have seen the carb butterfly valve pretty wet most of the times. Float valve should be something I try first? Where is it?

Since that post I have fixed two bad hoses. One was off and the other was crusty.

 

[AlTn]

Re: 1971 25 HP Johnson 25R71 after tune-up

last video sounded MUCH better!

 

[kfa4303]

Re: 1971 25 HP Johnson 25R71 after tune-up

Oh yeah! Looks and sounds GREAT!!!! Looks like y'all have lots of vroom-vroom fun in your future! Happy Boating!