Re: Johnson 70 timing
You can't judge how well it'll perform under load based on how it runs on the muffs. After sitting awhile, I'd rebuild the carbs before taking it out, just on general principle. High probability the hi-speed jets are gummed up. Also the water pump, soon as you get around to it. And gear oil change.
Water pump impeller (2 years) and gear oil (annually) are the only parts I change on schedule, before symptoms appear.
Your motor will run best with Champion QL77JC4 spark plugs at .030
Max recommended WOT RPM range is 4500-5500, prop it to run close to the upper end, a little over is ok.
Idle speed should be 900-950 in gear, pushing the boat. Set it at 1100-1200 on the muffs, then fine tune it after you get the boat in the water.
WOT timing is 19? BTDC.
Carbs have fixed jets, no mixture adjustments.
Make sure the choke plates are parallel, close fully when the choke is engaged, and stay open otherwise.
Make sure throttle plates are parallel, closed at idle and perfectly horizontal (not beyond) at WOT.
Refer to the picture below (it's a later model but the parts are all the same):
The idle set screw should be neither all in or all out, but it does need to be butted up against that throttle lever. If needed, adjust cable length using the black thumbwheel where the cable enters the cowl. The mark on the cam needs to hit the roller dead center (adjust the roller), else she'll fall flat on her face when you try to accelerate. Re-check throttle valves WOT position after completing these adjustments.
Finally, set the WOT timing (no need if you didn't take the flywheel off or mess with the timer base stop screw):
First set the TDC pointer (this needs to be done any time the flywheel is removed):
[note: Rotating the flywheel CCW turns the water pump impeller vanes backwards, so do it as directed for this procedure only, and as little as possible.]
1. rotate the flywheel (clockwise only) until the TDC mark is a few inches from the TDC pointer. Insert a piston stop tool into the #1 hole and rotate the flywheel (CW) until it contacts the stop. With a pencil, mark the edge of the flywheel at the TDC pointer.
2. rotate the flywheel (CW) a few inches past TDC, insert the piston stop tool, and rotate the flywheel back (CCW) until it contacts the stop. Mark the edge of the flywheel again, at the TDC pointer.
3. draw a straight line between your two marks.
4. draw a straight line from the center of, and perpendicular to, the first line to the edge of the flywheel.
5. if your 2nd line hits the 0? TDC mark embossed on the flywheel, you're done.
..........otherwise,
6. rotate the flywheel (clockwise) until the 0? TDC mark aligns with the TDC pointer.
7. loosen the TDC pointer and slide it over to align with your 2nd line.
8. repeat from step 1, until you hit TDC in step 5.
Then follow this procedure very carefully:
http://forums.iboats.com/showthread.php?t=228183
You won't find this in any manual...the manual will tell you it has to be done with motor running full throttle in a tank with a test wheel.
