1965 9.5 HP Johnson MQ-11C - Rough Idle Help

Hello to All,

As the senior member of our boating family, I was recently tasked with bringing back to life an old “Turtle”, MQ-11C. By inspection, this motor has lived a rough life, with about the only good things going for it when it arrived at my workshop being that it was not seized and had good compression (75 lbs. ea.).

The next thing I did was test for spark…only one plug wire was hot. I removed the flywheel and found one seemingly “original” coil and the other being a Sierra replacement. Interestingly enough, it was the Sierra coil that showed no spark. After removing this coil, I noticed that the HV wire end was heavily corroded. I snipped off about an inch of this wire, reinstalled the coil, and retested for spark. Both coils then tested good. Disclaimer – I don’t have a “spark jump tool” I have a plug-in tool that lights up when spark is present. It hasn’t failed me in the past on prior OB rebuild projects.

Feeling pretty good about the coils, I decided to go ahead and get some new parts coming. I ordered a new carb kit, tune-up kit, impeller, and T-Stat. I removed the old parts and installed these new ones without incident. Then, with freshly mixed gas on hand, I placed the motor in my test tank and began pulling….no luck….then after a squirt of starting fluid, she roared to life. Following several stops and starts, I was able to keep her running long enough to warm up. My hope was, after warming up she would “smooth out” and allow me to fine tune the low-speed jet adjustment…no luck….she never smoothed out….lots of coughing and sputtering, every time I attempted to slow her down this happened.

Having read many articles on this forum and others, I thought it may be helpful to provide you a bit more specifics as to exactly what I did in performing the repair work. First, the points were set to 20 with a feeler gauge and, as per J. Reeves, a size 22 would not pass through. The points were brand new and cleaned. The carb was completely disassembled, thoroughly cleaned (every orifice), and then reassembled with new parts and gaskets per kit. The initial setting of the low-speed jet was 1.5 turns out after first gently seating. The water in the test tank was well above the water pump and the exhaust contained plenty of water (not an overheating issue). The motor cowling was left off, eliminating the possibility of exhaust backfeed.

So, what’s your thoughts as to where I should begin a “deep dive”? Carburetor? Ignition? If so, where? I’m leaning toward this being a fuel issue, as she really comes to life with the starting fluid. One other disclaimer – how big of a deal is the “synchronizing fuel and ignition” adjustment? Quite honestly, it’s not very well written in the manual and I can’t say for sure I understand what they are trying to get across with “center of the mark”. What mark? I can sure see where the throttle first begins to move, but how do you correlate this with “a mark”? Could this lone adjustment be the entire source of my difficulties here? I’m thinking not, but would sure appreciate more guidance as to how this “synchronization” is supposed to work on this little 9.5 Turtle.

Thanks in advance for your feedback!!!

First synchronize throttle opening.-----It must not open too early.----Factory came out with an anti-vibration kit for the 64 / 65 models.----They shook too much at idle.----I was tasked with installing those in 1967 and 1968 on many of them.-----There is a cam on the magneto plate.----Find the mark on it.----Adjust the follower so that it opens correctly.

Very informative write up. We certainly need to confirm strong spark, your tester really won't do that. It confirms spark, but not how strong it is. First remove both spark plugs....I'm assuming they are brand new Champions. If you can grab your #2 Phillips screwdriver, insert it in spark plug boot, then hold the shank about 3/8" from a good ground. Then have a helper pull over the motor. The spark should be able to jump that gap, without fail. When you shortened the wire was it copper core? Did you replace the spring contact inside the spark plug boot? If they are rusty, it will weaken spark too.

If spark can jump a 5/16" gap why would a bit of rust stop it ?

Yeah, your probably right. Guess I just want to see it a nice clean connection. I use dielectric grease too.

Thanks for the feedback thus far. As for this mysterious "mark", I can't find it anywhere....as rare as a 3-legged unicorn.....is it an "etch" in the cam? is it located along the surface where the follower travels or is it on the upper side of the cam as viewed from above the flywheel? I see two "slashes" on the timing plate, but I'm thinking that's for setting the 180 degrees on the points.....right?

I removed the low-speed needle just to make sure it was properly assembled.....mine is the 4-washer design, with 2 cork washers squashed between 2 nylon washers, correct?

It is NOT the 2 vertical lines on the magneto plate .----Those are used to time the points to open at the correct time.

Thanks Racerone....you've confirmed my suspicion as to what the marks are NOT......can you please share with me what the marks ARE? Where are they? Again, an etch, dent? I don't know what to look for or where????

A cam that opens the carb throttle is on the magneto plate. That cam pushes on a vertical plastic rod. The vertical rod pushes on the lever on the carb throttle lever.

All that to say that the mark is on the cam close to the end that first hits the vertical rod as you come off dead slow position.

Fact----If throttle plate is open too early the carburetor idle circuit does not work !-----Throttle plate must be closed at idle.

So, if I can't find "the mark", can I just adjust the throttle (via cam follower) to begin movement at the beginning of the cam?

I am quite sure there is a mark on that cam.----Clean it and look carefully.

That's the general idea'. But I thought the problem was hard start without starting fluid, AND poor idle. That motor/year was not known to have great idle. They shook themselves to death. The reason for the vibration damper kit previously mentioned

thank you for your insight.....I've called it a night and am nursing an adult beverage to soften my failure....I'll look very close tomorrow and report back.

thanks again

Ah....yes, a fine glass of wine can ease all pain! Better check that spark, young man....forget that stupid cam....rarely find 'em messed up! Agree with Gator, not the best idling motors....but I'm thinking poor spark at low rpm's. When you idle it down and lean the low speed needle, does it "sneeze" on you? What's your mixing ratio? I have a dozen of these 9.5's around. Love 'em. I mix 64:1 on Amsoil Saber, or 100:1 Pre Mix Amsoil, but mixed at 64:1. Make sure crankshaft seals are good. If the seal will suck air, it will cause the motor to "sneeze" as well. Usually the result of ethanol fuel use. This motor uses rubber composition crank seals both top and bottom. Upper seal is most often the first failure. As Racer has mentioned in other posts, the seal will also spit out oil/fuel mix, and you will have signs of oil under the flywheel and often spilling on the block.

I just went through the same thing this last summer with one of those motors. I did all of the same things, carburetor kit, new spark plugs, tune-up kit, impeller, lower unit seals. The whole 9 yards. I also had to do a fuel pump overhaul as the diaphragms were rock hard and the check valves were shot as they wouldn't seal properly. After I did all of that it would start up and run 100% better than when I first got it. But I had issues at idle it wouldn't idle smooth and would cough and sneeze and then die out. If I richened it up it would no longer cough and sneeze but I couldn't get it to idle down low. So then I pulled the power head off to check the crankshaft seals. There was no oil residue around the top crankshaft seal and both of them felt nice and soft and look like they were making a good seal around the crankshaft. But I changed them anyways being I was that far into it and put the whole works back together. Then I took it back out on the lake and tried it out. That is one of the nicest idling motors I have ever used! It idles down just as nice as my dad's 1959 Evinrude 3 horsepower. It will idle down so low and so smooth the boat doesn't hardly move in the water. You can barely hear it running. Not says the seals are shot, but they will be eventually.. just my $0.02....

Agree, Brian. The crank seals really saved that one too. I think I remember a video you sent or posted on that repair. The fuel pump is also noteworthy. Why? A leak in the diaphragm which adds extra fuel into one cylinder, may not be noticeable at high speed, but causes a very poor idle.

BRUPP79 said:

I just went through the same thing this last summer with one of those motors. I did all of the same things, carburetor kit, new spark plugs, tune-up kit, impeller, lower unit seals. The whole 9 yards. I also had to do a fuel pump overhaul as the diaphragms were rock hard and the check valves were shot as they wouldn't seal properly. After I did all of that it would start up and run 100% better than when I first got it. But I had issues at idle it wouldn't idle smooth and would cough and sneeze and then die out. If I richened it up it would no longer cough and sneeze but I couldn't get it to idle down low. So then I pulled the power head off to check the crankshaft seals. There was no oil residue around the top crankshaft seal and both of them felt nice and soft and look like they were making a good seal around the crankshaft. But I changed them anyways being I was that far into it and put the whole works back together. Then I took it back out on the lake and tried it out. That is one of the nicest idling motors I have ever used! It idles down just as nice as my dad's 1959 Evinrude 3 horsepower. It will idle down so low and so smooth the boat doesn't hardly move in the water. You can barely hear it running. Not says the seals are shot, but they will be eventually.. just my $0.02....

Click to expand...

Must have had vibration dampers (??)

Hey Guys....thanks for all the feedback....I've got the magneto plate back off in search of "the mark", just to get that box checked first. I'm going to attempt to upload two pics I just took.....my novice eyes now see TWO "marks", about an inch apart. One looks like an indention or divot (on the top of the cam) and the other like a "1" (at the very beginning of the cam, on the face of the cam). So, now I need to know which, if either of these marks, is actually "the mark."

Here goes with the pics....may have to upload separately, I'm not sure....bare with me.

Size photos at under 1000k. Everybody loves to help with these great old 9.5's.
Note to Gator: I think Brian changed the dampers on that one, he didn't use the stock originals....but yes, it really ran sweet when it was done. That young man has some real talent.

First picture, that is the "mark" on top of the cam. I really don't know what that other one is on the toe of the cam.

Thank you, Mr. Gator sir!!! You are a scholar and a gentleman

Racerone....you were right on "the mark" (sorry, I couldn't resist). I've already made the adjustment (it was pretty much spot-on anyway), but will have to wait until I return (see below) for another attempt in the test tank.

Thanks to everyone who has contributed. I'm leaving tomorrow for a warmer destination for a few weeks. I was hoping to get this baby running smoothly before I left, but I've learned a lot and will dive back in when I return. I will keep you guys up to speed on progress and/or failures.

Assuming I still get the same sputtering/coughing as I attempt to idle down, what would be your first plan of action if you were me? Here's what I'm thinking at this point

1. Perform spark gap "jump" test as per timguy; if test is good,
2. Replace fuel pump - What is correct part number? I've found some conflicting information on this part. Mine is a square one...should I just get the kit?
3. Redo tank test; if coughing/sputtering continues....new crankshaft seals? Is this also referred to as the "top seal"; Other ideas before I go that far???

Here are some answers to questions some of you have posed along the way:

1. Gas is fresh, new, no ethanol; I use Quicksilver 2-cycle oil mixed at 50:1.
2. Plugs are New Champion J4C, gapped at 0.030.
3. Plug wires have copper core; I did not replace boots, but did re-terminate ends at each coil after snipping off an inch of wire. Inside of boots looked OK (not corroded). Fit snug on plug ends.

Thanks again guys!

A new factory diaphragm at less than $10 will be all you need to make the pump like new.----That little pump was installed on models in 2005.-----Somewhere in all the motors built year after year you will find the part # for just the diaphragm.-----Yes a new diaphragm is available !!

ebowles said:

1. Perform spark gap "jump" test as per timguy; if test is good,
!

Click to expand...

Build yourself a spark tester for free, you probably have scrap parts lying around. I didn’t invent this, but copied what others here have done.
THE 1/4” bolt will screw into the sparkplug boot & give a good connection. The other bare end, just stick into the sparkplug hole in the head, the weight of the device will wedge it on angle in the hole. Adjust the “sparking ends” to whatever gap you desire.
I put some stain on the wood to make the spark easier to see.
Racer does it even simpler, IIRC he just glued a couple of wires to a piece of cardboard.

OK, I've returned from much warmer weather.....it was great....hoping spring will be here soon.

Jumped back into my motor project. Went ahead and got a new fuel pump on order before I left, so that was 1st thing I installed. Placed motor back in tank and had same coughing issue. Made myself a "spark jumper" (thanks Edchris177) and tested.....all good there. Decided tear back into carb again.....recleaned, then back in tank....same cough. Finally, I think I made a breakthrough....while running roughly in the tank, I began experimenting with different things to see if I could smooth it out....no adjustment worked....BUT....when I decided to pump the bulb, I noticed some fuel drops from the hose running from the motor face to the fuel pump....the more I pumped the bulb, the better the motor began running....could all of this have been a loose connection on the fuel inlet hose? Now, I want to replace all hoses with new and can't seem to find information on the correct size IDs.....1/4, 5/16, 9/32 ??? Is the hose size from the pump to the carb the same as the inlet? Thanks gentlemen!

Supply hose is 5/16 and pump outlet to carb is actually 3/16.

OK, thanks....I'll go pick those up and report back soon on progress.

Just replace the one o-ring in each connecter?-----Or if beer tokens are not an issue buy a complete new hose.