engine timing..

[Caveman59]

1987 evinrude 70hp ELCOS, do these engines have a timing advance system ? If so how does it work and can it fail, working sometimes and not sometimes.. Bottom cylinder has 105 compression, has fuel and spark to the cylinder but makes no difference in the running of the engine when the plug wire is on or off,,,i have replaced every ignition part except the stator and it does test good on the multi meter..Thanks again Kevin ​

 

[jakedaawg]

Test spark on an open air gap spark tester set to 7/16"

what makes you say you are getting fuel to that cylinder?

what color stripe is on the oarnge wires going to each coil?

Timing is accomplished with the timer base, it seldom needs to be messed with unless someone with out knowledge started turning stuff on the linkage.

what was the compression of the other 2 cylinders?

have you torn down the carbs and cleaned them?

have you inspected Reed valves?

 

[jakedaawg]

Did you have the flywheel off? Reinstalled and torqued correctly? Flywheel key in good shape?

 

[Caveman59]

here is a few things I have replaced since this intermittent misfire. I have put new coils, ignition module, timing base, tested stator with a multi meter tested good, had all the carbs apart and fuel pump( everything was good all jets free flowing and clear of dirt, diaphragms good in fuel pump) all three wires to the coils are solid orange. compression on the other two cylinders is 120. I started the motor with the bottom plug out and it blew gas on my hand. spark plug has fuel on it. I have new plugs in and have switched plug wires around with the same result. it all started by boat running on a plane and suddenly losing a cylinder after idling for a bit it went back to three cylinders and ran fine. next time out ran on three for about 1/4 mile. then idled on two back to the ramp. threw more new parts at it and next time idled missing but soon as you hit the throttle would fire in all three and ran on 3 all day. drained all the fuel and refilled with premium, launched and ran about a 1/4 mi on three then dropped a cylinder. the rest of the time at idle went from 1-2 cylinders on the way to the ramp.

 

[Caveman59]

Did you have the flywheel off? Reinstalled and torqued correctly? Flywheel key in good shape?

I did have the flywheel off key was good went together good and torqued to spec..

 

[jakedaawg]

I might suggest that you verify that all the pins and sockets in the amphenol connectors at power pack are seated properly and to the correct depth.

Perform an open air gap spark check...does the spark jump 7/16"?

the oarnge wires should have a blue stripe for the top coil and a green stripe to the bottom coil...

Timing is not the problem unless someone messed with the linkage. You can not adjust timing for just one cylinder.

I prefer a spark checker that's let's you see all the spark at the same time...that way you can determine if the spark is properly sequential.

 

[Caveman59]

I might suggest that you verify that all the pins and sockets in the amphenol connectors at power pack are seated properly and to the correct depth.

Perform an open air gap spark check...does the spark jump 7/16"?

the oarnge wires should have a blue stripe for the top coil and a green stripe to the bottom coil...

Timing is not the problem unless someone messed with the linkage. You can not adjust timing for just one cylinder.

I prefer a spark checker that's let's you see all the spark at the same time...that way you can determine if the spark is properly sequential.

the spark does jump 7/16 while remaining a strong blue spark..it will jumpover 1/2" you can hear the zap..all of the connectors in the new power pack are like resin in place..what is crazy about it is after everything that has been done it will at times run on all 3 cylinders and run good then the next time out misfire like hell

 

[jakedaawg]

Were these aftermarket parts? If they are CDI brand contact them, they are very helpful.

Verify all grounds to each component are tight and clean.

Make sure the spark plug wire is run through the insulated clip to keep it from getting close to the cowl latch. That is usually a v-4 issue but is possible on others.

Test key switch.

You will have to perform the spark check while its having an issue. If all else fails it may be the weak compression?

 

[Caveman59]

Were these aftermarket parts? If they are CDI brand contact them, they are very helpful.

Verify all grounds to each component are tight and clean.

Make sure the spark plug wire is run through the insulated clip to keep it from getting close to the cowl latch. That is usually a v-4 issue but is possible on others.

Test key switch.

You will have to perform the spark check while its having an issue. If all else fails it may be the weak compression?

I would think weak compression too. but at times it clears up and runs fine. all parts were oem except timing base was CDI thanks

 

[jakedaawg]

Well, maybe the bottom cylinder is flooding from a poorly installed needle/seat, improper adjustment, various other reasons....a bad fuel pump diaphragm depending on the pump...etc.