1969 40 hp Evinrude coughs at idle

[JPickett]

To say the least I thought I like many have replaced everything on this engine to make it as close to as new as I could. Here is the list of replacement parts.
Coils, points, condensors, plugs, plug wires...Engine wiring harnes, new fuel lines, rebuilt carb, then had it set and linked by a professional shop. Lower unit resealed, along with a new water pump.

So here is how the problem came about. The engine fired and idled flawless, then all the sudden it would just cough then idle for 5-8 more seconds then cough. It would do this until the I brought the rpms up to the 1k range. It would do this in or out of gear. The engine would run fine all the way up to full rpm. I finally stopped and opened the inspection door and noticed that when the engine coughed it would squirt fuel out around the hose and the hose barb on the carb. I replaced the origional wire type hose clamp with a small screw type hose clamp. That solved the fuel leak, and about half of the cough problem. I had to richen up the low speed needle 1/8 turn to solve the coughing. I will admit that the fuel was purchased in late May and had stabil added at the same time. What do you believe caused the coughing, and is what I did the correct way to solve it?

Second problem of the day

A little time passed and it started to feel like it the prop was cavitating. I checked the rpm no gain, pulled the prop, no slipping of the hub. Then for some reason I checked the primer bulb. It was dry. After no joke over 100 pumps on both tanks it wouldnt take prime. I could hear the fuel being drawn into the hose "not the bulb" then it fall back into the tank. I finally held the bulb vertical and rapped on the check valve end with a screwdrive and it took prime. This solved the cavitating feeling. I am guessing that the check valve got stuck. Is this common or a common thing with Walmart primer bulbs?

Thanks for all your help and I am sorry for the long post. Here are a few pics of the engine fully restored.

 

[tx1961whaler]

Re: 1969 40 hp Evinrude coughs at idle

Beautiful motor! Mine would look like the "before" part of the restoration, since mine has been outside since 1969, been used a lot in saltwater, and is now made up of various parts of 3 different outboards. I couldn't deal with the electric shift, once it started acting up.......
The mixture adjustment was what fixed the cough, and was the proper thing to do. It's hard to get them adjusted until it's actually on the water.
Yes, third-party fuel line assemblies can be a problem. I have an Attwood assembly that I have to beat on sometimes.
Is the cable (wire rope) on your steering in good shape? I thought I could see a little discoloration at the end of a cable in the photos, but maybe it was the lighting. Make sure to inspect the steering system regularly, since it's pretty bad if something lets loose while underway.

 

[DJ]

Re: 1969 40 hp Evinrude coughs at idle

She's a beaut!

I was going to say that you have a 'lean sneeze'. The mixture really needs to be set while in the water or a test tank.

Even at that, changes in weather and barometric pressure may affect it, especially if it's set on the lean side.

Nice to see one in that condition!

 

[JPickett]

Re: 1969 40 hp Evinrude coughs at idle

Thanks for the compliments. I just got the paint layed down last weekend. That was a chore in itself. I had to have it hand blended. Yall probably know that the paint is not to be found.

TX1961WHALER. My cables and pulleys are next to be changed. The cables are still okay, but the vinyl cover has discolored. The pulleys just started to crack. So I will be on the hunt for those soon. So I figured while I had it all out the cables would be changed as well.

DJ. come to think of it the humidity was in the high 80's when I last ran/set the carbs with the temp in the low 100's. That being said those conditions were a far cry from the 40% humidity and high 70 temps of last Saturday. I had the carbs set in a tank. But while at the lake I reset them while tied to the dock. I put the engine in gear and set it. I still cannot get the rpm's as low as I would like, but I am not gonna trust my tach. I think I will pull the tiny tach off my big Scag mower and set the rpms, then make a note of how off my in dash tach is.

 

[F_R]

Re: 1969 40 hp Evinrude coughs at idle

Great job!! May I ask what you used for the electrical cable covering? Looks like regular automotive stuff, is it? Did you get it at an auto parts store?

Your coughing is what is commonly called "lean sneeze". It is because of not enough fuel for the amount of air being drawn in, which varies slightly with prevailing temperature. That is what the adjustment on the carburetor is there for. You did right. The setting varies slightly according to prevailing air temperature, but the thermostat on your Lark should hold the engine temp pretty stable once it warms up.

 

[JPickett]

Re: 1969 40 hp Evinrude coughs at idle

Thanks. I will admit that I can set a carb on a automobile like its old hat. But when it comes to these older engines I am lost. I guess it stems from being so fearful of messing something irreplaceable up.

FR that cable loom I scavanged off of a min 1980's Evinrude troling motor. I couldnt find anything that would open up wide enough to go over the master connection on the wiring harnes. But that stuff worked like a dream.

 

[charliedaubitz]

Re: 1969 40 hp Evinrude coughs at idle

What prop did you use, mine has a 10 1/2 x 12 and I haven't run it yet. I think I may need a 10 1/2 X 13 for my 15" aluminum boat with the same motor as yours. Did you replace both vacuum lines, Mine were bad. There are 2.

 

[tashasdaddy]

Re: 1969 40 hp Evinrude coughs at idle

your high speed jet is fixed, it is deep behind the drain plug on the carb bowl, but the low speed is adjustable. Joe Reeves graciously provide these instructions.

(Carburetor Adjustment - Single S/S Adjustable Needle Valve)
(J. Reeves)

Initial setting is: Slow speed = seat gently, then open 1-1/2 turns.

Start engine and set the rpms to where it just stays running. In segments of 1/8 turns, start to turn the S/S needle valve in. Wait a few seconds for the engine to respond. As you turn the valve in, the rpms will increase. Lower the rpms again to where the engine will just stay running.

Eventually you'll hit the point where the engine wants to die out or it will spit back (sounds like a mild backfire). At that point, back out the valve 1/4 turn. Within that 1/4 turn, you'll find the smoothest slow speed setting.

Note: As a final double check setting of the slow speed valve(s), if the engine has more than one carburetor, do not attempt to gradually adjust all of the valves/carburetors at the same time. Do one at a time until you hit the above response (die out or spit back), then go on to the next valve/carburetor. It may be necessary to back out "all" of the slow speed adjustable needle valves 1/8 turn before doing this final adjustment due to the fact that one of the valves might be initially set ever so slightly lean.

When you have finished the above adjustment, you will have no reason to move them again unless the carburetor fouls/gums up from sitting, in which case you would be required to remove, clean, and rebuild the carburetor anyway.

 

[JPickett]

Re: 1969 40 hp Evinrude coughs at idle

Tash Thanks for that carb setting info. I had seen that b/f but had not been able to find it. I will deff. Try to find that sweet spot. I had it out this weekend and it ran flawlessly. I had to back out the s/s 1/8 turn and it set up on its idle like a new one.

Charlie I am running a 10 3/8 x14 in. prop on mine. The Old Chiltons guide that I have says that this about this prop. 33, 40 HP all years. 13-15 ft. light loads 26-35 mph. My boat 14.5 straight measurment from bow to stern. With it fully loaded it will plane at 1/2 throttle and will do 27 mph at WOT. I usually run the engine trimmed in the farthest hole from the transom. If the water is rough or its windy the boat will want to porpus so I will back it in one hole. This wont affect the top speed on my boat but it will not plane out as high out water as the farthest hole position.

I didnt change the vacume lines on my engine. I truthfully didnt even think of changing them. One of those hoses is right under the bottom cylinder isnt it? If so where is the 2nd hoses? I would love to know. I mean what is a few more dollars for a little more peace of mind.

 

[charliedaubitz]

Re: 1969 40 hp Evinrude coughs at idle

the vac lines are both located under the carb on the block, one high and one low. the high one is a little bigger than the lower and goes to the vac switch next to the starter. the smaller one goes to a barb under the stator plate about above the vac switch, at the top part of the block. Both of mine were bad, cracked and leaking.

 

[JPickett]

Re: 1969 40 hp Evinrude coughs at idle

Thanks, I will throw a vac test on them and see if they need to be replaced. Might replace them anyway. I think I need to find out why by battery is draining overnight. Anyone know if it would drain if it was hooked to a bat charger and the power went off for 6 hours? I only had 30% capacity left after it went off.