Logo
FULL SITE MENU

1976 Evinrude 70HP Timing issue

C

cobburn

New member
Hello all,
I have an 1976 Evinrude 70hp that has been a pain for me as I am trying to get it going for my brother. Compression test good all cylinders. Power pack is new, carbs have been cleaned twiec now. Synced the linkage but I think it still off. stator output is good. good fuel, new plugs. If i hold the the timer base back with my hand all the way and give it throttle it will rev but as soon as I move the timer base forward it bogs and dies out. brother replaced the stator and if I am correct you can't clock it wrong when installing it?? we are pretty sure the key is in the flywheel and that is good although we are going to double check that along with the stator clocking if it is even possible to clock it wrong. I just wanted some advisement before we dig back into her. any ideas or suggestions would be greatly appreciated. also I need to know the idle timing spec as to where the timer base should be and how to I check the timing and what kind of timing light/tools do I need? -Burn
 
Last edited:
If the flywheel key was sheared, even ever so slightly... the engine would not run at all.

Quite unlikely the idle timing or full spark advance setting is off unless you changed it... just make sure that the scribe mark on the cam aligns with the center of the throttle roller just when the throttle butterflies start to open.

Double check the linkages between the carburetor throttle butterflies to make sure that one of them isn't set wrong. The butterflies (all of them) should just start to open and close at the same exact time... you do not want one of them slightly open at idle when the others are closed.

Carburetor modification bulletin sent via email. Timing light should be an induction type light but the wire thru lights will suffice. Tools... timing light, 7/16" open end wrench, spark plug wrench, regular screwdriver. Timing specs... see your service manual. Timing procedure as follows:

(Timing At Cranking Speed 4°)
(J. Reeves)


NOTE: If your engine has the "Fast Start" feature", you must disconnect/eliminate that feature in order to use the following method. The "Fast Start" automatically advances the spark electronically when the engine first starts, dropping it to normal when the engine reaches a certain temperature.

The full spark advance can be adjusted at cranking speed,"without" have the engine running as follows.


To set the timing on that engine, have the s/plugs out, and have the throttle at full, set that timer base under the flywheel tight against the rubber stop on the end of the full spark timer advance stop screw (wire it against that stop if necessary).


Rig up a spark tester on the #1 cylinder plug wire. Hook up the timing light to the #1 plug wire. Crank the engine over and set the spark advance to 4° less than what the engine calls for.


It's a good idea to ground the other plug wires to avoid sparks that could ignite fuel that may shoot out of the plug holes. I've personally never grounded them out and have never encountered a problem but it could happen.


I don't know the full spark advance setting your engine calls for, but to pick a figure, say your engine calls for 28°, set the timing at 24°. The reasoning for the 4° difference is that when the engine is actually running, due to the nature of the solid state ignition components, the engine gains the extra 4°.


If you set the engine to its true setting at cranking speed, when running it will advance beyond its limit by 4° which will set up pre-ignition causing guaranteed piston damage! You don't want that to take place.


No need to be concerned about the idle timing as that will take care of itself. The main concern is the full advance setting.

A fellow member from one of the various marine forums suggested having water supplied to the water pump (flushette or barrel) simply to provide lubrication to impeller. A worthwhile suggestion I thought, and entered here.


Be sure to use your own engines spark advance settings, not the one I picked out of the air here in my notes.

Thousands of parts in my remaining stock. Not able to list them all. Let me know what you need and I'll look it up for you. Visit my eBay auction at:

http://shop.ebay.com/Joe_OMC32/m.html?_dmd=1&_ipg=50&_sop=12&_rdc=1
********************
 
all of the butterflys are dead even with each other, i do have the scribe line off, thought it was to be lined up with the throttle completely closed thank you for that. I have been trying to follow my clymer manaul but its for many years and models so i dont think it has everything you need to know. Are these motors very sensitvie to where the timing is in relation to the butterflies? it seems so. I am going to go back through everything again and try. right now at idle I can still push the timer base back (retard) a little. Without knowing exactly knowing what the idle timing is ive read it should be all hte way back?? or just disregard that and it will be where it will be when set at 4 degrees. the full advance on this motor is 17 degrees. It has has been a learning process surely so in the beginning I probably have adjusted things I shouldn't have. The carbs do not have an "x" on them to state the have been modified but I think they need to be. Why would they would for so long not modified and then need to be? I see where others have had a problem that the modification fixed but seemed like it they were fine for many years. also it does crank over like the timing is too far advanced at times too. I will have to start from the ground up and double check the keyway and all linkages and timing settings.
 
ok I've reread your post so I may have restated/confused some of the info so my post may have been restating some of that. Thanks for your help.
 
If that engine ran properly in the past, it's highly unlikely the carburetors would require modifying.

It is more likely that when cleaning the carburetors, the high speed jets that are located horizontally in the bottom center portion of the float chamber... way in back of the drain screw/plug... have been overlooked and are somewhat clogged. If so, clean them with a piece of single strand steel wire as solvent just doesn't do that job properly.
 
Well after a hiatus from the boat (it's my brother's so he gets easily frustrated and has to take a break from it.) and it's time to get back into it. I set the timing as it was way advanced and that helped. I have not modified the carbs per the bulletin as I still can't get over if they have been working for so long like that then why all of a sudden? With the timing set closer to correct it still was bogging down. Put some premix in a spray bottle and was able to get her to open up. The bottom carb seemed to be of issue so after being sure of clean carbs we finally noticed one of the reeds on the bottom cylinder isn't opening up...certainly makes sense. Tat's where we are now so hopefully I can report a better outcome soon!
 
The high speed jets are located horizontially in the bottom center portion of the float chambers.... way in back of the drain screw/bolt. Sounds like at least one of them is clogged... clean them thoroughly.
 
????-----------There is more than one reed petal and if one stays closed while cranking the motor that does not indicate a huge problem.
 
Back
Top