1970 4 hp evinrude lightwin running on one cylinder

this motor has been tuned up, the carb has been completely rebuilt, and the ignition system has been tuned up as well. Most of the time it is running the engine only runs on one cylinder and when it runs on both it misfires very often. The points are set to .020 and the spark plugs are new champion J4C set at .030. I did a spark test, and I saw a big fat blue spark jump across both spark plugs at the right time, every time. At this point the only problems I could possibly think of that are causing this is either
1. The air/fuel mix is for some reason not being burnt in one cylinder
or 2. no or not enough air/fuel mix is being delivered to one cylinder, therefore it does not fire.
pretty much everything in this engine has been fixed up, I don't know why this would be happening. could it be low compression in one cylinder? Maybe I should try a decarb or something? or maybe something shorts out in the ignition system from the vibrations of the running engine, so when I do a spark test (engine is not running) is comes out as successful, but that success does not translate to two firing cylinders during operation?

I used to have it running great, they're amazing little outboards (when they work properly )

any help/suggestions would be greatly appreciated

Re: 1970 4 hp evinrude lightwin running on one cylinder

Use a timing light while the engine is acting up and check the spark on each cylinder. Maybe you have a coil breaking down under load. Do both plugs look like they are burning the same?

Re: 1970 4 hp evinrude lightwin running on one cylinder

I agree with above. Coils often wait until they are warm before they give trouble. You could also fire it up in the dark and have a close look to see if spark is jumping to ground somewhere. Despite your findings of good spark it has me thinking your spark does fail. I'd be interested in knowing what your plugs look like too. I hope no water is present. Best of luck. Rick.

Re: 1970 4 hp evinrude lightwin running on one cylinder

What is the compression on each cylinder?

Re: 1970 4 hp evinrude lightwin running on one cylinder

both plugs look pretty much the same, though the plug that goes in the top cylinder has some oil on the electrode while on the bottom it seems drier. and the compression is at 97 psi on the top, and 94 on the bottom. unfortunately I don't have a timing light :|

EDIT: And no water is present

Re: 1970 4 hp evinrude lightwin running on one cylinder

Dumb question; the spark plug wires aren't switched are they?

Re: 1970 4 hp evinrude lightwin running on one cylinder

You can get a Spark gap tester at most automotive store for about ten bucks. It has an adjustable gap you can set at 3/8ths of an inch. When your motor is showing symptoms put it on each plug wire and see if one is not giving good spark. Or you can pull the wires one at a time and see what happens. If one makes no difference it is not firing if one causes the motor to quit it is the one that is working. Rick.

Re: 1970 4 hp evinrude lightwin running on one cylinder

okay it turns out it was only running on one cylinder because the high speed jet was open way too far, so I turned it for a leaner mixture and it runs on both cylinders now. But it still misfires almost all the time, should I like get out on a boat or something and fiddle around with the needle valves until it runs the way it should? (assuming that is even the problem...)

Re: 1970 4 hp evinrude lightwin running on one cylinder

Glad your making progress. The book says to set the final settings on the water with your boat unrestrained (not tied to dock). I think it is most important for setting the hi speed though. Rick.

Re: 1970 4 hp evinrude lightwin running on one cylinder

Ugh.. still having problems. I have never personally replaced the condensers, and they look kind of old.. what is their exact purpose anyways? How do I test them? One of them could be causing my severe misfiring problems, maybe from a loose connection inside of it or something but I wouldn't know because I have no clue whether they are completely functional or not.

Re: 1970 4 hp evinrude lightwin running on one cylinder

Well that could be the problem. I know they store voltage but beyond that I'm not to sure. I know they have to work or they wouldn't be there. Have you done your needle settings on the water? I would do that first. Did you ever get a spark gap tester? Rick.

Re: 1970 4 hp evinrude lightwin running on one cylinder

Alright, unfortunately I am unable to get a hold of a spark gap tester, but I just did a very thourough spark test (took out spark plugs, connected them to the spark plug wires and wired them to ground on the motor and turned over the engine) and the spark is the same colour and size on both plugs, and both seem to be timed perfectly with the in and out motion of the pistons. I've went through and tested pretty much every part of the ignition system and it is working perfectly at least to my standards, so this extremely rough performance has got to be caused by something else.

Maybe it's my carburetor? I have put a kit into it, though I never got a new float because the old cork one looked practically in mint condition, though when I recently put the carb back together the float was not EXACTLY parallel to the float bowl.. didn't think it needed to be, does it? It just seems unlikely that it would be causing my problem. Either way, I'm gonna take apart the carb again (ugh) and make sure everything is lined up perfectly. Is it recommended that the float is replaced with one of the newer plastic ones?

Other than that the carb is completely clean and free of dirt.

After that ill get out on the water and try to set the needle valves to see if I can get the engine to run properly, but that could take quite a while. (Ill let you know when I do)

Re: 1970 4 hp evinrude lightwin running on one cylinder

Don't just re look at the carb. Re-clean it and blow it out well with compressed air. It does sound as though your spark is fine. Any chance you've got some bad fuel? Rick.

Re: 1970 4 hp evinrude lightwin running on one cylinder

Will do, I hate taking the damned thing apart so much though :facepalm:
As for the fuel, the gas in my tank was purchased last year, but I put stabilizer in it..
I think the fuel is fine though as I used it to fire up this engine for the first time this year a few weeks ago and it was working absolutely perfect then

Re: 1970 4 hp evinrude lightwin running on one cylinder

Well it is possible your gas is too old. It would be one more easy variable to eliminate if it were me. Rick.

Re: 1970 4 hp evinrude lightwin running on one cylinder

okay, looks as though I'm gonna be needing a carb kit. some gaskets seem worn out and I just don't trust that cork float. took everything apart and made sure all passages were completely clear.
will also be getting a fresh tank of gas.
I might as well get a new head gasket as well as the one I have seems to leak oil or something.
I live near Vancouver, know of any places I can order from online in BC so I don't have to wait for customs to clear the parts over the border?

Re: 1970 4 hp evinrude lightwin running on one cylinder

Funny you should ask. I just got a recommendation today from a fellow who was very impressed with a parts place in Vancouver. He was especially happy with the shipping costs. Last week I needed a power pack and the price was about 120.00 but shipping was an additional 42.00 which really makes the pack too expensive in the long run. No ones fault, it's just the way it is. I'm having computer problems and can't get to my opened email. I'll send you the company name when my P.C. is back up and running. It should be tomorrow morning. Rick.

Re: 1970 4 hp evinrude lightwin running on one cylinder

alright then let me know when you find it

Re: 1970 4 hp evinrude lightwin running on one cylinder

Check your message box. Rick.