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1974 Evinrude 50 HP ignition problems

B

bb56

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Hello I am looking for some help on a problem I have with My outboard it is a 1974 Evinrude 50 hp Model 50472M. Once it is started it will run smooth for a few seconds and then it catches and the RPMs go up as if it either got more fuel or one cylinder kicked in. I have been completely through the fuel system rebuilt carbs replaced fuel pump and fuel lines clear back to the tank. It also has new plugs and coils a new stator timing base sensor and a new power pack. I replaced these items based on what I had been told by a mechanic who looked at the boat last year when the problem first cropped he also said I should replace the timer base but it seems to be in good condition. My question is are there wires or something internal other than the sensor to the timer base that would cause it not to work? and could it cause the problem I am having.
 
Check the compression. What are the psi readings of the individual cylinders?

S/Plugs removed... Check to see if the spark will jump a 7/16" gap on all cylinders with a strong blue lightning like flame... a real SNAP!

Spark plugs should be Champion L77JC4 or QL77JC4 plugs gaped at either .030 (long life) or .040 (strong spark)

Let us know what you find.
 
Thank you for your response Joe
I am going to have to get a compression tester to test compression but I do remember that the mechanic said one cylinder had less compression than the other. I want to say it was 10 psi less than the other. I tested the spark and it was very weak and intermittent it would not jump a 7/16 gap. I went through all the tests that came with the ignition parts the stator brown wire to ground tested 465 Ohms DVA voltage connected was 0 when I removed the brown wire and tested it it was 230 V. The timer sensor was 19 Ohms between the white black and black white wires, white black to ground was open, as was black white, no DVA output on either of the sensor wires when brown stator wire was connected and they were .19 V when brown stator wire was disconnected. I checked the kill wire and it had .01 V with key off and .02 with the key on. I also disconnected the rectifier wires from the stator to see if it made a difference no change. The literature from CDI said if the stator output was good when the brown wire was disconnected the power pack was bad but it is brand new and when I did the test with a AA battery for trigger signal it tested good although the spark seemed very weak and the DVA output at the terminals for the coils only registered 10 V on my meter which seemed rather odd unless I was reading it wrong. The plugs that are in the motor don't match the numbers you recommended they are surface gap plugs that were called for in the manual but I will try one of those other plugs and see if it makes a difference
Thank you for your assistance.
 
Compression gauges are fairly cheap and if you intent to continue boating, it will be in demand.

Keep in mind that the engine must turn over fast, at least 300 rpm in order for the stator to generate the proper AC voltage to the powerpack capacitor, needed to energize powerpack. A slow cranking engine will emit weak, erratic, or no ignition/spark.

If a slow cranking engine... run good known jumper cables from a good known fully charged battery directly to the starter. If that makes a world of difference rpm wise, clean all cable/wire terminal ends associated with the electric starter including the battery terminals and all components that the cables/wires attached to.

The surface gap plugs that you mention (probably UL77V) are cold nature plugs regardless of what their heat designation states and are prone to fouling. I (and many others) avoid them like the plague with few exceptions.

Carefully and closely view the stator to see if any sticky looking substance is dripping down from it upon the powerhead area. If so, the stator has failed regardless of whatever readings you may obtain.

Keep in touch.
 
Thanks Joe
Bought a compression gauge and checked compression #1 cylinder was at 110 and #2 Read 100 one time and 105 another time. It seemed like I had pretty good rpm when cranking the motor but I cleaned all the terminals and grounds anyway the stator is brand new and I didn't sticky substance at all. I replaced the plugs as you suggested with the champion QL77JC4. Started the motor and it runs without the surging it was experiencing before. Its just a little rough at idle but I probably should check the timing and the carburetor adjustments as the mechanic who looked at it before played around with all those when trying to diagnose the problem. I haven't checked it yet at wide open throttle but it looks like I may be back in business. Thank you for your insight and assistance.
 
Hello Joe
Today was the first time I had to work on the motor since your last post. Started the motor with the warm up lever up and slowly pushed it down but at lower RPM the motor wants to die I adjusted the carburetors to get it to stay running. I shut it off then could not get I checked the spark and it is still very weak I don't know how it even started. At this point I am about to give up and take it to the local boat shop.
 
The engine must crank over at least 300 rpm in order for the stator to generate the proper AC voltage to the powerpack capacitor... a slow cranking engine will emit weak, erratic, or no spark even with all of the ignition components in new condition.

If the engine is cranking over normally (FAST)... see if you could borrow a different known good stator to try as that's what it sound like it could be... that is if the engine is cranking over fast.

Is this how you adjusted the carburetors?
(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 1: 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.
 
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