timing a '77 Evinrude 85

[DaMoos]

I have 1977 Evinrude (85799S) that I am trying to time.

My biggest problem is that the book I have covers many models for a decent range of years, and evn when I read the part that seems to be for my year/motor, it describes adjustments that my motor doesn't seem to have.


Here is what I have so far. To get the pick up timing right, the book made it seem like there was a screw that would rotate the cam that interacts with the carb throttle lever to where I want it to be. The only way I see on my motor to do this was a plastic piece threaded onto the control arm that could only be adjusted by removing 2 cotter pins, and unhooking the cam to free it. A combination of messing with that and adjusting the contact on the carb achieved lining up the mark correctly. I think I did this right, but it was no where near what the book described, and thus my discomfort.

The other and more difficult issue is the actual timing and idle. Here is where I am greatly confused.

My understanding is that at idle, and for the initial range of acceleration the throttle plates remain closed and the engine is accelerated solely by timing advance, until a certain point after which the throttle plates open in concert with the timing continuing to advance.

The book says I am looking for 4-5 degrees BTDC at an idle RPM of 6-700. My confusion is this. The motor "sounds" decent at around 8-900 rpm. At that rpm, the timing is almost at TDC, assuming the pointer is correct. I can advance the timing, but obviously the rpm will go up.

The book implies that I should be able to adjust timing and idle separately, but I see no way to do this. I don't see how I can advance the timing while maintaining the idle rpm I should have. My understanding is that the carb has fixed orifices, so what else is there? Once the throttle plates are closed, what other way besides retarding timing is there to slow the idle?

I just rebuilt the carbs if it matters. I leveled the floats, if that makes a difference. The engine runs the same as it did pre-carb rebuilds.

 

[Bosunsmate]

Re: timing a '77 Evinrude 85

Before you do timing its important to know the motors different systems are running right. You have rebuilt the carbs, have you checked that all cylinders are sparking and have you also checked compression?
Your idle rpm will seem decent as you say at a higher rpm if somethings not right in the engine.

You should also check that tdc is at 0 on the pointer and flywheel.
I agree with you, i cant see how you can adjust idle and timing independently when you have fixed orifices.

Have you checked what your max timing is at?
If your idle timing is at tdc then is suspect your max advance timing might be too far advanced and you would risk engine damge if you kept it at that for any decent period

 

[emdsapmgr]

Re: timing a '77 Evinrude 85

I don't recommend you get into timing issues unless you are working from a factory manual. The 4-5 degrees is a suggested timing at idle. Those stated idle timing degrees are only a suggestion-as an initial number/setting-after an overhaul. You set the timing by setting the idle rpm's: float the boat in the lake, shift to forward and then set the idle rpm's to 650-700. When you get it to idle at that rpm's the idle timing is set correctly-regardless of the degrees-for your boat only. The factory would have you adjust the WOT timing when the engine is under power at 4500-5000 rpm's. This is not a normal thing a consumer can tackle on this engine. Suggest you look for an alternate procedure in the "top secret" files-the top thread at the first line of this forum page. It's a procedure by Mr. Reeves, and can be done statically/at idle. Best to verify the timing pointer setting (by the factory manual) before you try to validate your WOT timing. If, after reading the factory service manual, all of this seems Greek-let a skilled marine tech set it for you.