Logo
FULL SITE MENU

1975 Evenrude 70HP ignition problems

R

route11

New member
" I'm working on a 1975 Ev

" I'm working on a 1975 Evenrude 70 HP that has ignition problems. My fishing buddy just purchased it and it ran great the first time out. On the second trip to the river, it quit and wouldn't restart. Cylinders one and two weren't firing and three had a weak spark. He purchased a Clymer Evenrude/Johnson outboard repair manual and I volunteered to try repairs.
A fully charged Eveready deep cycle 115 amp marine/rv battery is in the boat I've installed a new stator ring that produces exactly 175 volts AC and tests at 727 ohms, slightly higher than the given range of 555 - 705 ohms. The three ignition sensor coils tested at 8.3, 9.1 and 9.3 ohms, within the specified 7.5 - 9.5 ohm range.
I still have a weak spark at coil three and don't have spark at coils one and two unless I disconnect coil three at the power pack. One and two then have a strong spark. If I switch the power pack coil lead from coil three to terminals one or two of the power pack, it then throws a strong spark. Any one of the three coils connected to terminal three kills one and two. I've checked the power pack ground and it's good. I've removed the key switch lead at terminal six (which doesn't change the problem) and checked the circuit to the ignition switch (the black/yellow lead is fully grounded only in the key "off" position.)
The repair manual tells how to check the power pack with a spark tester, which I don't have. I need to rely on sparkplugs pulled from the motor and grounded for spark testing and a timing light. Anybody have any ideas how to do check the power pack without a spark tester, or am I overlooking the problem altogether???? "
 
"Route11..... A poor mans spar

"Route11..... A poor mans spark tester can be rigged by simply inserting the proper size philip screwdriver into the plug bubber boots so that it is within the metal spring like terminal that normally grabs the spark plug.

Hold the shank of the screwdriver away from the block approximately 7/16" which is the called factory gap setting for testing.

The cranking of the engine should be performed by jumping the starter solenoid.... battery cable side of the solenoid to one of the 3/8" nuts containing the wire that energizes the solenoid, not the ground wire 3/8" nut. And absolutely NOT from one large solenoid terminal lug to the other!

Remove the spark plugs. Turn the ignition key to the ON position. Crank the engine and observe the spark. If no spark or erratic weak spark, disconnect the main electrical RED plug at the engine. Crank the engine again and observe the spark. If you now have proper spark, which would be a strong blue lightning like flame jumping that 7/16" gap, replace the ignition switch.

If the spark is still non existent or erratic and weak, replace the powerpack.

Joe (30+ Years With OMC)"
 
" Joe - thanks a bunch! My fri

" Joe - thanks a bunch! My friend really wants his boat for this coming week which is his vacation. I'll try the screwdriver thing in the morning and hopefully have the problem narrowed down. Since ordering parts for either fix will be needed, do you know any suppliers that can do overnight or express mail with my charge card? "
 
I am changing the spark plugs

I am changing the spark plugs on my off shore boat . For grins I ohmed them . To my suprise none of them ohmed the same .What should spark plugs ohm at .They are 135 Mariners dual using NGK BU8H .Will this affect the performance of the boat?


Larry
 
Back
Top