1961 Evinrude 18 won't idle

[bonvicken]

In order to hold an idle, I have to set the idle adjust screw so high that the idle point is past the timing mark on the throttle cam...even set this high, the engine gradually slows down and will die if I dont give it a little more throttle. Smokes a lot 'cuz it's running really rich (throttle is open but it's running at low idle speed). Runs fine at WOT. Hesitates a little when going from idle to WOT, but then picks up and runs fine. I've replaced the coils, points, plugs, condensers, properly gapped the plugs and points. Cleaned and rebuilt the carb. Is this a reed or crankshaft seal problem?<br /><br />Thanks for the help, I've lurked around this board for a long time and this is my first post. I've gotten a lot of good info, and this is the first time I haven't found the answer in the archives.

 

[Paul Moir]

Re: 1961 Evinrude 18 won't idle

It could be, at least the symptoms sound familair to me. Compare the insulators on the firing end of your spark plugs. If they're different, that can point towards a crankcase leak.<br />Invariably, the leak will only be in one crankcase half, causing the engine to run leaner on one cylinder than the other. 'Reading' the sparkplugs will show the problem if the leak is bad enough.

 

[zantz]

Re: 1961 Evinrude 18 won't idle

Does it idle real rough? Check the compression with a gage. My motor had some of the same symtoms and it turned out to be scored cylinders.<br /><br />Why do you have it set rich? Will it not idle at all set correctly?

 

[bonvicken]

Re: 1961 Evinrude 18 won't idle

Originally posted by Zantz:<br /> Does it idle real rough? Check the compression with a gage. My motor had some of the same symtoms and it turned out to be scored cylinders.<br /><br />Why do you have it set rich? Will it not idle at all set correctly?

Doesn't idle rough, it just slows down and quits. The idle adjust jet has absolutely no effect, since the point at which it's 'idling' is past the timing mark on the throttle cam; i.e. the throttle is starting to open (this is why it's running rich, not because of idle adjustment). Engine won't run with the throttle fully closed. I've rebuilt the carb, and verified that the idle circuit is clean.

 

[bonvicken]

Re: 1961 Evinrude 18 won't idle

Originally posted by Paul Moir:<br /> It could be, at least the symptoms sound familair to me. Compare the insulators on the firing end of your spark plugs. If they're different, that can point towards a crankcase leak.<br />Invariably, the leak will only be in one crankcase half, causing the engine to run leaner on one cylinder than the other. 'Reading' the sparkplugs will show the problem if the leak is bad enough.

Thanks, I run it for a while and check the plugs. I checked the compression; it was 80 lb on both cylinders, but I don't trust the Harbor Freight gauge I bought....I checked the compression on a 10 horse I have, and it read 50 lb on both cylinders. That motor runs perfectly. Anybody else have any experience with these gauges?

 

[R.Johnson]

Re: 1961 Evinrude 18 won't idle

Inside the float bowl, there is a washer shaped gasket called a boss gasket that slips down on the high speed fuel nozzle. If the gasket is shrunk, or missing, the carb will suck outside air and not idle. As for your compression guage! I don't know as I've ever seen two in agreement. What you are looking for is the difference between cylinders. One thing that can effect readings is the tire stem like check valve at the inlet end, keep this clean, and don't over tighten. I have heard not to use tire stems, but I don't know if this is true, or not. You can buy these stems from a Snap-On, or Mac tool route man.

 

[bonvicken]

Re: 1961 Evinrude 18 won't idle

Originally posted by R.Johnson:<br />[QB] Inside the float bowl, there is a washer shaped gasket called a boss gasket that slips down on the high speed fuel nozzle. If the gasket is shrunk, or missing, the carb will suck outside air and not idle. <br /><br />Thanks, R.Johnson, I rebuilt the carb, has a brand new boss gasket. Compression on both cylinders (according to my gauge) is within a pound or two.

 

[Solittle]

Re: 1961 Evinrude 18 won't idle

Your symptoms strongly point to a carb problem even though you rebuilt it.

 

[bonvicken]

Re: 1961 Evinrude 18 won't idle

Assuming the idle circuit is clean and the boss gasket is OK, what else should I look for?

 

[Paul Moir]

Re: 1961 Evinrude 18 won't idle

Air leaks around the mixture control valves (tighten the packing), needle valve leaking (does pumping the primer bulb cause the carb to flood or have any effect with the engine running?).<br />Assuming the idle circuit is clear. Poke out all the orifaces with a wire. There may be two on your carb, one fore and one aft of the throttle plate when it's closed.

 

[R.Johnson]

Re: 1961 Evinrude 18 won't idle

Check to be sure the fuel pump to by-pass screws are tight, and the gasket is not shrunk. Lower, to upper main bearing recirc hose is not cracked, or broken.

 

[zantz]

Re: 1961 Evinrude 18 won't idle

I agree with these guys, since your compression is good. My cousin had a 15HP that would cut out and die. It turned out to be the fuel pump, but when he got the fuel pump fixed, since he messed with the mixture screws, it ran too rich, and died at idle, until he reset them. Spark plugs do tell a lot about how the engine is running. Best to pull them right after it dies.

 

[bonvicken]

Re: 1961 Evinrude 18 won't idle

Thanks, guys, appreciate the input. Don't think it's the needle valve, I can pump on it all day and the motor doesn't flood. The packing on the low speed jet raised a flag with me, though. When I rebuilt the carb, I put it back together exactly the way it was when I got it, but there was no bushing or packing washer on the low speed jet like there is in the parts breakdown. Do I need the washer for an airtight seal (the washer goes between the packing nut and packing). Also, it the bushing something that sticks up inside the low speed hole, or would it fall right out when taking the nozzle out? What does the bushing do, and would the lack of the bushing be a reason for my motor not idling?<br /><br />Thanks, <br /><br />George

 

[Paul Moir]

Re: 1961 Evinrude 18 won't idle

Oh, do you mean the thing that appears to be a cylindrical thing that goes into the carb first? If so, that bushing is actually the 'nut' for the low speed needle valve. That is to say, it is actually what the valve threads into. Normally, it doesn't ever come out, as it's been pressed into the carb.<br />If the needle valve is difficult to turn, your getting a good seal. Usually people reporting here who have air leaks at the adjustments also have problems keeping the adjustments in place while the engine is running, since they're so loose they vibrate out of position.

 

[bonvicken]

Re: 1961 Evinrude 18 won't idle

Oh. Dang, thought it was gonna be easy. Packing is pretty tight, enough so that the needle doesn't go anywhere when the motor's running. I've made that mistake before.

 

[bonvicken]

Re: 1961 Evinrude 18 won't idle

Been gone for a few days (Muskie tournament up north) and haven't been able to mess with the motor 'til today. Swapped the fuel pump with a known good one, that didn't fix it. I noticed that the problem got worse as the motor warmed up; i.e. she'd run down below the timing mark when cold, but after she warmed up a bit, the minimum point at which she'd keep an idle was at or above the timing mark. When cold, she didn't seem to bog down, either. Ran the motor in a 30 gal garbage can, so I didn't get it above fast idle. Checked the plugs, the top one was darker and oilier than the bottom, bottom was fairly white with a little oil on it. They're fairly new plugs, don't know how long they have to run to get a 'tan' appearance on the insulator. I guess I should mention that one of the coils went bad a few weeks ago, replaced it with a new OMC part, and the spark on the new coil wasn't as good as on the old. Had problems on the water with one cylinder intermittently cutting out, so I replaced the new OMC coil with one from another motor I have. When turning the flywheel by hand (using a wrench on the flywheel nut), the spark on the replaced coil still didn't seem as strong as the one originally on the motor, but now it runs OK at wide open. Don't know if turning the flywheel in this manner is a good spark test (hard to get the same speed for both sides), but the 'weak spark' cylinder is the one that has the blacker plug. I don't think it's a bad condenser, I've swapped them and the problem doesn't follow. I also noticed that the original coil (not the original part on the motor, it's a replacement) has a higher resistance on the secondary coil than the new ones I put in. Both replacements were around 4.5k, the original is about 6k ohms. Could this problem be caused by weak spark on one cylinder, or is the difference in plugs due to a secondary compression (crankcase seal) problem?<br /><br />Thanks a lot for the help, you guys are awesome!<br /><br />George

 

[bonvicken]

Re: 1961 Evinrude 18 won't idle

Thanks for all the helpful input, guys. Based on SoLittle's advice, I tore down the carb and really concentrated on the idle circuit using Gumout and a can of compressed freon. Got 'er back together today, ran in a barrel and after tweaking the idle jet, she purrs like a kitten...this old girl will idle all day. I just stood there and watched in amazement. Boy, am I a geek, my neighbors (and my wife) think I'm a nut. Going on the river tomorrow, thanks again for all the help.