71 Johnson 9.5 HP not revving out

[lexkyboater]

This old motor starts and runs good at low rpm. I've already replaced water pump, lower prop shaft seal and fuel pump. At WOT, squeezing the bulb doesn't help to make it run better (although it did before the new fuel pump!). I've rebuilt carb (didn't replace expansion plugs) and made sure I blew out the high speed jet and the port, and even made sure the jet was .048 with a drill bit. It was initially quite gunky. I also replaced points, plugs and condensors, but not the coils and plug wires. Plug wires seem in decent shape. Coils checked out with primary and secondary resistance at 1.0 ohms and 7 thousand ohms, respectively. Adjusted points according to the excellent article at http://outboard-boat-motor-repair.c... 5.5 HP 1954-1964 Ignition System Tune-up.htm, under the section "A simple but effective method to test the ignition timing." If you haven't seen this before, you should take a look. I've always blindly gapped my points at 0.020 or whatever at the top of the cam lobe but this guy correctly pointed out that's just a starting point. When the points open, the plugs fire, and you need to set them to open with the timing mark on the flywheel.

Noticed that there are broken sections of insulation on the wires going from the points to the stop button/kill switch. Bought some electrical sealer/liquid tape and am going to try sealing those wires just in case. The coils look like they've been replaced as they have a nice rubber coating around them, but the wires going from the coils have old looking insulation on them, so may try the electrical sealer on them too. Haven't run at night yet to see any arcing. Link and Sync done when carb was rebuilt and the butterfly on the carb opens all the way up as the timing advances. Looks right. Am also in the process of decarbing, and have sprayed it 3 times now and letting it sit for the day with Deep Creep.

Took out yesterday morning and it ran good and clean for about 5 seconds, then started missing/bogging and slowing down and stops planing well. Seems electrical to me. I took the flywheel off again and found that I hadn't tightened the screw on the front coil's condensor. When I tighted it back down, still missing and won't rev out. Since that condensor wasn't tightened down, did that ruin it? I bought two new condensors just to make sure but haven't replaced yet. I also haven't checked that the plugs are firing consistently after taking them out and holding them to engine ground. Maybe I have a few things left to do, but I've had this thing out 5 times now and will hopefully get it solved. Any other tips?

 

[Bruce San]

Re: 71 Johnson 9.5 HP not revving out

Have you tried running it with the cowl off at WOT? (in gear on the boat)

 

[lexkyboater]

Re: 71 Johnson 9.5 HP not revving out

Not yet. Are you saying do this at night to see sparks jumping or am I looking for something else?

 

[Bruce San]

Re: 71 Johnson 9.5 HP not revving out

The exhaust housing seals go bad on those motors and exaust will build up under the cowl and starve the engine of oxygen because it's breathing exhaust. sounds like the symptoms you describe. especially when you said it starts out running fine and then bogs.

It's worth a try.

 

[lexkyboater]

Re: 71 Johnson 9.5 HP not revving out

Hadn't ever heard that - that's good information - but I did pull the cowl at the lake yesterday and run it a few minutes in an attempt to see any problems. When I killed it, replaced the hood, then took off again, it was still bogging. That 5 seconds of clean running is the first time it's ever done that since I've owned it. But I've always had 2+ minutes of no-wake zone and yesterday I didn't because I launched at a main lake access location. Hmmm. I'll definitely try running it with the cowl off though tonight.

I have had bad condensors on my '59 Ford 601 tractor and it ran rough, even at low idle, but didn't know if they could go bad because of a lack of ground.

 

[Bruce San]

Re: 71 Johnson 9.5 HP not revving out

You'll do that in the lake right? Just don't ever rev a 2 cycle without a load on it. You'd hate the results.

Let us know how it goes.

 

[lexkyboater]

Re: 71 Johnson 9.5 HP not revving out

Absolutely! I've heard you shouldn't even rev the bigger motors much above idle on the muffs. I did start the decarb process at the lake yesterday, and the wind shifted and started blowing all my white smoke at the marina, and I thought, "oops." I went back home and put it in a trash can and it blew all my white smoke at our house. I'm sure my wife loved that...

BTW, I'm pretty sure I've got a new exhaust seal on the exhaust tube when I replaced the water pump. But I did notice that it seemed awfully big compared to the size of the exhaust tube, and I wondered how it would seal. Hmmm...

 

[Xcusme]

Re: 71 Johnson 9.5 HP not revving out

I have had bad condensors on my '59 Ford 601 tractor and it ran rough, even at low idle, but didn't know if they could go bad because of a lack of ground.

The condensers won't go bad from loosing their ground connection, they just won't work. If the condenser is shorted internally, now that's a different matter. The condensers job is to hasten the collapse of the primary coil winding when the points open. The condenser absorbs the current that would arc across the points when the points open. Without the condenser, the points contact surfaces would arc and pit rapidly. Electrically, the condenser (or capacitor) is in parallel with the point set.

 

[iwombat]

Re: 71 Johnson 9.5 HP not revving out

Its time once again for ask Dr. Science . . .

The condenser's main function is to minimize what's called "ringing" and it's by-product, arcing.

Any electrical coil acts as a damped driven electrical oscillator as it fights itself due to electrical induction while passing current (Lorentz law and all that). The condenser essentially flattens the discharge curve and prevents the high voltage produced in the coils from arcing back across the points and causing them to foul.

 

[F_R]

Re: 71 Johnson 9.5 HP not revving out

Way back earlier, it was said the coils have a nice rubber coating on them. Really? They are not normally rubber coated. Are we missing something? Maybe somebody has patched some cracks?

 

[lexkyboater]

Re: 71 Johnson 9.5 HP not revving out

Thanks for all the extra education guys. Those coils have a factory looking coating on them, and it looks kind of like rubber. I'll get some pictures tonight. The primary and secondary resistance did check out...

 

[lexkyboater]

Re: 71 Johnson 9.5 HP not revving out

I ended up running it last night after clipping the wires off the kill switch and removing the connectors and it seemed to run better, but still would not plane well and rev out. The wires were in bad shape and the insulation just fell off after I tried tugging on it at the clip that holds them down (thanks to iwombat's advice in another thread). But at least it doesn't seem to be missing anymore. I think the kill switch wires were probably intermittently grounding out. See attached pic. I didn't end up replacing that condensor, and I think it's okay. Also is attached a pic of my "rubber coated" coils. I scratched at them and that's what seems to be on them?

Also, it seems to run a little better without the cowl at speed, maybe a little better plane (1 - 2 mph?) but mostly just louder. I tried removing the cowl with it sitting in a trash can at home at low idle and with no wind mind you, and exhaust rolling up towards the carbs, it does die when I put the cowl back on. I attached a pic of my new water tube grommet and water pump. Doesn't seem like the water tube grommet would fit the exhaust tube tightly, but it at least is new. Running at night but with a 3/4 full moon and didn't see any sparks jumping anywhere.

I also checked the spark with the plugs out this morning, and the top plug threw a weak whitish-yellow spark, and the lower threw an even weaker yellow spark. Didn't look very strong to me. Don't know if this is a problem, but my local boat shop gave me Champion J4C plugs, instead of J4J that a Clymer manual recommends. What do you guys run in these motors, and will J4C be okay?

Another question - I noticed that pulling the starter rope even with the plugs out is very tight. When I replaced the water pump, after I got the water pump housing snugged down, I couldn't even turn the drive shaft anymore by hand with the lower unit separated from the motor. Is this normal? I was turning the drive shaft as I was tightening the housing down per recommendations in the manual so it doesn't pinch the new impeller. On the first pull of the starter rope of the day, it is typically very tight, then gets easier on subsequent pulls. When cold, it starts in 2 or 3 tries, and when warm, will easily start on the first pull.

But the biggest problem I found this morning is that the compression is only 68 psi on both cylinders. Odd that they matched exactly. Checked after running it a few minutes in a trash can this morning. After that, I decarbed with Deep Creep a fifth time and am letting it sit all day. I'm spraying 2 - 5 minutes each time and letting it sit for 5 min - 10 hours. Lots of white smoke rolls out, but it gets less each time. I think I'll spray some deep creep in the cylinders directly with the cylinders up and let it sit overnight tonight, then blow it out with the plugs out.

 

[iwombat]

Re: 71 Johnson 9.5 HP not revving out

I wouldn't worry about 68psi on a rope start. They're dead even and it idles good. That's all you really need to know about compression. Forget about the number.

J4C is the replacement for J4J, it's what you should be running.

Did you do a spark test with a spark tester, or was that just using the plugs? You probably want to do a real spark test at this point and eliminate any ignition issues.

Those motors will collect exhaust gas in a barrel. That it only ran a little better w/o the cover tells me that it just got a little extra boost from being leaned out and exhaust leakage is not an issue.


My money is on coils, condensers, plug wires or all three. A bad condenser usually leaves behind some charred points. If that's the case replace both the point-set and condenser. Inspect your plug wires. If they look bad replace them. Be sure to get solid core marine plug wires, not carbon core automotive wires.

Those coils are normal, and they are not the original set (that's good!). That crankshaft might need a little dressing up with steel wool or emery cloth before setting the flywheel back in. Looks like it's got some good ridges on it.

 

[lexkyboater]

Re: 71 Johnson 9.5 HP not revving out

Thanks for help! The "spark test" was just with the plugs. I'm not a big time mechanic yet so I wonder if I should get a real spark tester for future use or just pick up some new coils? Or both? Yellow sparks don't seem good. Do I need a marine or 6 volt spark tester? What should I see in terms of numbers on the spark test (I've never used one)? The points, plugs and condensors have been recently replaced, but I do have two new condensors I could put on just to make sure.

Agreed on the lean running with the cowl off. Do the burrs on the crankshaft cause uneven movement of the flywheel and cause uneven fire due to the distance between the coil and the flywheel?

 

[iwombat]

Re: 71 Johnson 9.5 HP not revving out

A spark tester is just a c-clamp looking thing. You can easily make one yourself with some nails. The idea is to create a 7/16" gap between two metal points. one side is grounded, the other side is hooked in to your plug wire. 7/16" in the air simulates the load across your spark plug's gap in the combustion chamber under pressure and fuel mix.

To make one at home put three nails through a board in a straight line. on the back side, put 90-degree bends in the outside two. Solder or securely wrap a grounding wire to the middle nail (side opposite the bended nails). you can turn the bended nails to get that 7/16" gap with the center nail. (well on a 9.5 ignition 7/16" may be a bit much - probably 3/8" or 1/4") Attach both plug wires to the nail heads on the outside nails (the ones with the bends).

Pull away.


If that made any sense you'll have plug wires and ground wire attached to one side of the board. A center post and two bent nails on the other side. You should see some nice bright arcs from the bent nails to the center post.

Those burrs in the crank will cause the flywheel to not seat properly and potentially sheer the key.

 

[lexkyboater]

Re: 71 Johnson 9.5 HP not revving out

Okay, got the spark tester made. Put unused plug screw-on terminals on my nails for the plug wires to connect to and worked out great. Initially, could only get the top cylinder to fire at 1/8" gap, and the bottom at 5/16". Replaced coils, and in the process found that wiggling the top plug wire produced an open circuit. So replaced plug wires with good 7 mm copper core Tractor Supply replacements. Retested spark and got only 5/16" gap jump on both, but nice blue sparks. Also reset points and verified .020 gap. Verified old coils have secondary resistance of 77,000/80,000 ohms, where new ones were at 92,800 and 93,800. Old coils had primary resistance of about 1.0, but forgot to check new ones, but since I'm getting good spark should be alright. Okay, so ignition should now be solid.

Went for a lake test and have about the same results - maybe 8 - 10 mph and about half way planed off by myself on a 14 foot aluminum v-bottom. Rpms seem really low to me. Tried pulling choke and that causes it to about die when at WOT, so that means it's getting plenty of gas. Seems that now I have verified ignition, compression, that leaves gas/carburetion. I have rebuilt the carb but didn't replace the core plugs, but TashasDaddy says he replaces and seems not too bad to put new ones in. The larger core plug is leaking a little on my carb and both plugs are no longer rounded, but flattened. Also, I did not soak the carb when rebuilding - I just blew it out, but it seemed to be clear after I was done. Maybe not? I guess I can reuse the new but now used gaskets again when reinstalling carb? Also, have gas that is 4 months old but did mix in a fresh gallon, but am going to try all new gas.

I'm also concerned about my water pump. It seems real stiff after the new housing and impeller I recently replaced. The first pull of the starter rope is real tight and stiff. Subsequent pulls are easier, and the engine seems to idle and rev out okay in neutral. Is this a problem? It also makes a racket of rubber squeaking against the housing when pulling the starter rope when it's out of water (like to check point gap). I guess that means the water pump is working and it's pumping water good. Have also replaced thermostat.

Next steps?
1) Replace gas
2) Clean gas tank
3) Complete Deep Creep decarbing (have done this 5 times and still getting smoke)
4) Replace carb core plugs
5) Check reeds when running by holding card to carb throat to see if mists or heavy gas blowback
6) Pull carb and soak this time
7) Can it turn that big 8 1/8 x 8 prop anymore?

Agreed, or would you change order or try something else? This is getting frustrating at this point, and no longer seems like a fun project - it's now work! Thanks for all the help guys!

 

[ezeke]

Re: 71 Johnson 9.5 HP not revving out

Clean and rebuild the carburetors first. When all is said and done, you will probably find that cleaning out the high speed jets will give you the most improvement. Because they lie horizontally at the bottom of the float bowls, they are the first things to clog up.

 

[lexkyboater]

Re: 71 Johnson 9.5 HP not revving out

Alright guys, got this fixed! The final problem ended up being more of an adjustment/setup problem with the carb though. After I cleaned the carb a second time, letting it soak after pulling the carb core plugs, I set the idle rich/lean adjustment, and went to the lake. It did the same thing, essentially not revving out. I decided to turn the rich/lean idle speed adjustment knob in to lean out the carb, and it took off! I turned it some more, and it took off again. My problem was that it was just running too rich to clean out and run. At that point I was getting a wake crest about 10 feet behind the boat, and then I tilted the motor out to the max adjustment and got another 2 mph! The wake crest was then around 14 feet behind the boat. This thing was scatting! Probably upper teens. All that may indicate my high speed jet has been reamed out a little and could either use a new one or one jet leaner for best results. I verified it as close as I could with the blunt end of a drill bit, but I didn't have one that's exactly .048 inches in diameter, so it's not exact. Here's some additional things I either learned or needed to remind myself:

1) Those idle adjustment screws wear out with age, which allows more gas to pass by it. I ended up setting mine just a little more than 1/3 turn out.

2) You must set your idle adjustment rich/lean mixture before trouble-shooting the high speed jet. That's because the idle port still feeds the cylinders at high speed. If it's rich at low speed, it's probably rich at high speed, unless there's a problem with the high speed jet. See attached pic, which I adapted from http://au.geocities.com/ozcross250/needles.html.

3) Always confirm jet orifice size, if possible. In my case, it's .048 inches on the high speed jet. Someone could have reamed it out in cleaning it, and that could cause performance issues.

4) Always remove those core plugs when rebuilding carbs. In my case, I had a good amount of crud behind the top core plug and some glazing on the small ports under the lower core plug. If these aren't cleaned, you may be removing the carb and cleaning a second time like I did.

5) Always ensure, prior to each lake test, that air, fuel, fire and compression are all still good. Carburetion is the most complex, but that doesn't mean ignition is always working. My engine had multiple problems, which I had to isolate and resolve before it worked well. After replacing the fuel pump, points, condensors and plugs, it still didn't run right. Compression remained stable at 68 psi, but I had a plug wire that had an open connection, preventing good fire. I then had a plugged high speed jet which cleaning fixed, but then had to lean out the mixture for it to open up and run. Plus the engine sat for at least a year before I acquired it. Just needed some TLC.

Thanks for all the help on this thread and this forum. I definitely couldn't have resolved everything without the expert advice here! --Steve

 

[iwombat]

Re: 71 Johnson 9.5 HP not revving out

Good to hear it's all good now.

#5 is sure a key one, isn't it?

 

[lexkyboater]

Re: 71 Johnson 9.5 HP not revving out

You betcha, and it sure saved me some frustration on that final lake test. After all the work I'd done, and not knowing that compression and spark were still good, I would have probably gone back home irritated with the whole thing. Since I knew and had confirmed my compression, spark, and carb (including low speed adjustment) were all good before heading to the lake, I probably would not have found the problem.