Re: WOT Timing Procedure Evinrude V4 115 SPL 1998
Sure....
It is just as I described it....but varies from motor to motor. (Maybe that is why it is not widely recommended...too many variations...)
Anyway. I am going to go real basic here, OK?
As you know, timing on these OBs is all mechanical. The timer base rotates under the flywheel to effectively change the point in time when the pack is triggered to fire.
Optical is the same way, but it uses a light source and wheel with slots in it to trigger the pack. The wheel with slots simply rotates around as you advance the throttle.
You can watch the movement on the timer base models fairly easily. Just look up under the flywheel while you advance throttle (engine OFF). TB will rotate around and hit some sort of stopping device. Maybe a metal boss, maybe a screw with a rubber tip on it...something to positively stop that TB rotation when the throttle is at WOT. It rotates about 25 degrees from idle position to WOT position.
So, with that in mind, you will study your complete throttle linkage and find a very conveninet place to disconnect the timing function from the throttle function. It will be there somehere. On my V6 loopers, you just pop the TB timing rod loose right where it attaches to the TB. It is very easy. Some models will require a different method.
Once you have that TB disconnected, and you can advance it by hand, you are ready.
Rig up a manual way to move the now loose TB. I use a piece of coat hanger bent to a hook. KEEP THROTTLES CLOSED. Start engine, muffs, etc....let it warm up to correct operating temp, get your timing light ready, and slowly advance the timing all the way to the stop by manually rotating the free rotating timer base.
THE THROTTLE WILL ALWAYS REMAIN CLOSED.
The engine will rev up, race up to maybe 2500 or so, but it will not go much beyond that. The engine is now at WOT timing because the timer base is against the stop. You check the timing, let's say like on my engine V6 looper....and find for instance it is at 16*.. OK, shut engine down, adjust the stop, re-start and check again. Once I get 18* (my spec, yours might be different), it is set and will probably never need checking again, unless TB or flywheel is changed.
So, it is not as complicated as it sounds. Just find that linkage separation point, disconnect it, start engine, rotate TB manually to stop, check timing and set as required, reconnect linkage.
Go boating.
EDIT:
I have used this method on V6 loopers, V4 crossflows, three cyl 70s and an old Force 50.
I have not used it on an optical yet, but should work.