Re: Joe Reeves I need some info
(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.
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(Compression & Spark Test)
(J. Reeves)
1st - Regardless of what problem one might encounter, always start with the basic troubleshooting procedure. Check the compression which should be in the range of 100+ psi (somewhat less on the smaller hp engines) and even on all cylinders.
2nd - With the spark plugs removed, rig up some type of spark tester whereas you can set a gap to be jumped. On magneto ignition systems.... and also the Battery Capacitance Ignition system OMC engines from 1968 to 1972, set the gap to 1/4". On the solid state OMC ignition systems from 1973 to the present, set the gap to 7/16". The spark should jump the gap with a strong blue lightning like flame..... a real strong blue snap!
NOTE: Checking the spark via using the spark plugs is a waste of time and proves nothing. The above stated gaps must be used for a proper test.
If there was no spark, on engines from 1973 up (If the electrical plug exists), disconnect the RED main electrical plug at the engine. Remove the s/plugs. crank the engine via the starter solenoid (jumper bat term to small 3/8" term nut, not the ground nut) and observe spark. If spark is now okay as stated above, the usual cause is a shorted ignition switch BUT that black/yellow wire could also.be shorted to ground at some point wthin the wiring harness.
For the later model engines where that large RED electrical plug was discontinued for updated electrical connections, find the black/yellow wire leading to the powerpack and disconnect it to run the above ignition switch/wiring harness test.
If the above checks out as it should, and the engine dies out when throttle is applied or won't idle, it is usually due to one or both of two things. The carburetors are fouled, in which case the cure would be to remove, clean, and rebuild them..... or the timer base under the flywheel is sticking which would result in a retarded spark. If the engine will not fire/start at all even though you have the proper spark and compression, it's usually due to fouled carburetors.
To check the timer base for sticking (Engine Not Running), spin the prop to align the shifter dog with forward gear and while doing so, put the engine into forward gear. Now, while watching the timer base, slowly apply throttle clear up to full throttle. The timer base should move smoothly all the way up against the black rubber cap that is atached to the end of the full advance spark setting screw. If the timer base sticks, find out why and correct that problem.
Usually any sticking of the timer base is caused by one of the four retaining clamps being slightly too tight. Putting a very thin washer under the clamp cures that problem. Some boaters use a thin screwdriver to bend the clamp upwards slightly but I prefer the thin washer. The sticking can also be caused by having a faulty stator start to melt down, resulting in a sticky substance dripping down on the timer base nylon retaining ring.
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WATER PUMP
Remove long shoulder bolt from shift linkage under bottom carburetor. Bolt is horizontal and is removed sideways.
Scribe a mark on the trim tab and lower unit so that the trim tab is replaced in the same exact location.
Remove all bolts that retain lower unit including the one under the trim tab.
Drop the lower unit, remove the water pump, replace as needed.
DO NOT turn the shift rod! the measurement is critical. If it is turned, the shift will be faulty!
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Parts replacement..... stator, reg/rectifier, etc.... make notes, take pictures before removing, don't rely on memory! Assembly is simply the reversal of taking something apart.
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Link/Synchronization......
The scribe mark of the cam should be dead center of the throttle cam roller just when the throttle butterflies are just starting to open.
Linkages between carbs should be such that the butterflies start to open and close all at the same time.
Unless you've changed the distance on the rod (nylon threaded item) between the vertical throttle lever on the engine and the metal scribed cam... leave it where it is, otherwise you'll need to set the idle timing.
