1967 Evinrude 9.5 missing at low speeds

[iwombat]

I have a 1967 9.5 that runs rough at low speeds, rough enough that it's tough to hold a troll. Rebuilt carb, new plugs, set points. I haven't checked compression, but would weak compression cause an intermittant miss? I don't suspect bad compression anyway. Runs the same with cover on or off. Coils look pretty new, but I suppose it could be a cracked insulator.

Other ideas?

 

[tashasdaddy]

Re: 1967 Evinrude 9.5 missing at low speeds

email me i'll send you Joe Reeves carb adjustments, mine now runs like new and it's a '55 15hp.
tashasdaddy@comcast.net

 

[Scott in MN]

Re: 1967 Evinrude 9.5 missing at low speeds

Could be a bad spark plug wire? (Intermittent)

 

[tashasdaddy]

Re: 1967 Evinrude 9.5 missing at low speeds

could be, are you getting spark , the carb adjustment is simple and worth while. can't send till this evening, on different puter.

 

[iwombat]

Re: 1967 Evinrude 9.5 missing at low speeds

since it runs fine at high rpm I'm assuming spark is okay. Once I crank it down past "shift" it begins to miss.

 

[iwombat]

Re: 1967 Evinrude 9.5 missing at low speeds

Here's where I admit I'm a 2-stroke noob. (I normally live in 4-stroke
land with a small fleet of motorcycles and hot-rods.)

How important is decarbonizing at regular intervals, and is there a way to do it w/o removal of the head?

Head removal as part of routine maintenance has me a little out of my element as you can well imagine.

 

[tashasdaddy]

Re: 1967 Evinrude 9.5 missing at low speeds

you do not have to remove anything to decarb a 2cycle. you tank 3/4 to a gallon of gas put 16oz of Seafoam 3 oz of oil. you run on this mixtures until the engine gets good an warm , stop engine let sit 20 min to 1 hour, repeat sequence. it is going to smoke like a hiouse on fire. keep repeating until it pretty much quits smoking.. then take out on the water and run hell out of it. woeks thesame on a 4cycle just leave the oil out.

 

[ezeke]

Re: 1967 Evinrude 9.5 missing at low speeds

See if the motor speeds up if you pull the choke out a little while running. If the motor speeds up, you are running lean.

The service manual says to turn clockwise until gently seated and then back out 3/4 turn. That is a good starting point for the 9.5.

 

[iwombat]

Re: 1967 Evinrude 9.5 missing at low speeds

I've followed the procedure in the service manual and have it pretty much narrowed down to about a 15-degree range on the dial. Which, incidentally is about 2/3 turn. Thanks though.

And thanks a pile for the decarbonizing procedure. Saves me a trip to the dealer for a head gasket. The service manual recommends popping the head. It seemed a bit extreme.

 

[tashasdaddy]

Re: 1967 Evinrude 9.5 missing at low speeds

that was before the days of chem cleaning, althought seafoam has been around a long time.

 

[iwombat]

Re: 1967 Evinrude 9.5 missing at low speeds

I think I'll check the compression, decarbonize (with the old spark plugs) and then reset the low-speed adjustment afterwards. We'll see how it goes. Infrared temp sensor says the engine is chugging along at 147F at the thermostat housing, so we're good to go there.

My guess is excessive carbon build-up (maybe a stuck ring) and improper low-speed mixture in combination.

I've got a spare parts motor, so if that doesn't work I'll put it on the bench and carefully inspect the ignition components and swap out anything that looks odd.

Here's hoping it stays off the bench.

 

[iwombat]

Re: 1967 Evinrude 9.5 missing at low speeds

Well it went on the bench. I found some worn wires and some stripped outer housing on a plug wire. A little soldering, splicing, and heat shrinking was necessary for the coil leads. Plug wires just got shortened by an inch or so. Too late to run it tonight, we'll see what happens tomorrow.

 

[tashasdaddy]

Re: 1967 Evinrude 9.5 missing at low speeds

not to sound obsessive but has the engine sat up for a period of time? if it has ,do the impeller, before you run it hard.

 

[iwombat]

Re: 1967 Evinrude 9.5 missing at low speeds

Not particularly. It was another person's regular runner until he got a 15hp. The low speed setting was all the way up to "shift" so I don't think he ever ran it as a trolling motor.

 

[iwombat]

Re: 1967 Evinrude 9.5 missing at low speeds

Well it seems that the bad insulator or wires were the problem. This motor screams now. However, how low can these things idle? I'm all the way down on the cam (to the timing mark) for low speed setting now and it still seems pretty fast. Must have only been running on one cylinder before. I have compression under 100, maybe low compression keeps it from running slow. Can't exatly figure that out, but oh well. Anyway, it seems to be a lot healthier now.

 

[tashasdaddy]

Re: 1967 Evinrude 9.5 missing at low speeds

should idle at 700 in neutral, 600 in gear, in the water. low compression will effect idle. it will have to idle higher in order to shift. in the near future you need to address the comp. issue, dragging a cyl is not good.

 

[iwombat]

Re: 1967 Evinrude 9.5 missing at low speeds

Lake tested and approved. High idle is still a bit of a problem, so it probably won't see any salmon fishing this year - I use an electric for trout. I plan on rebuilding the powerhead on the parts motor this winter, then swap out later. As it is, it should see me through the summer a little zippier than my 6hp.

Thanks all for the support.

While we're on the subject, is a rebuild kit for the powerhead available? I haven't been able to locate one yet.

 

[iwombat]

Re: 1967 Evinrude 9.5 missing at low speeds

I'm also not exactly sure I got good compression measurements anyway. It's a little hard to hold the tester against the back of the motor while pulling the cord in the front. Next time I'll find a partner. I sure wish I had a threaded compression tester fitting.

 

[freddyray21]

Re: 1967 Evinrude 9.5 missing at low speeds

if you are getting just under 100 with one of those compression testers you probably have over 100 with a threaded one

 

[iwombat]

Re: 1967 Evinrude 9.5 missing at low speeds

Good to know. I generally don't bother with compression tests and
just do leakdowns. I'm guessing leakdowns would be next to useless on a 2-stroke.