Re: Black Max 150 has me baffeled
OK, here we go.
The throttle lever moves the timing and the butterfly throttle valves on the carbs in sync. Usually, on a merc, you start out at idle with the carbs fully closed, and the timing at the idle setting for the motor, (somewhere ATDC, 11* on mine.)
As you advance the throttle, it advances the timing. At some specified time (immediately on mine) a cam starts to open the carburetor valves and add fuel and air. About half way open on the carbs, the timing hits the maximum, (23* BTDC on mine). The timing change is accomplished by a linkage that rotates the trigger assembly under the flywheel. When that rotates, the wires connected to it, (7 on a v6) move with it. They can rub, wear, bind up, and otherwise either get damaged, or restrict the rotation of the trigger. I've seen folks replace a voltage reagulator and strap down the wiring with tie wraps and prevent timing from advancing past 10* or so. The freedom of that gang of wires is critical. Mine is carefully laid on top of all other wires and hoses on the top and starboard sides of the engine, and the first strap that holds it is half way down the switchboxes.
The early V6's had a high performance (sort of) bayonet fuel connector on them. When I got mine, it had been replaced with an aftermarket connector, and it just wouldn't flow enough fuel at WOT to keep up with the pump. I could feel it, and I put on a pressure gauge and could document it. The final fix turned out to be to just remove it and run the hose directly to the oil mixer. Along these lines, clean filters, proper sized hoses (Just use Mercury hose) good primer bulb (again mercury or OMC only, no aftermarket) are critical.
The other item is if you seem to have some sort of erratic firing, or unexplained damage to the power head, it's worth while to set up a dial indicator or depth gauge (I use a $25 digital caliper from Menards, or little machine shop tie wrapped to a fitting I made by welding a tab of steel to a gutted out spark plug) to set the timing mark for all the cylinders. Merc specs have you set a mark on the flywheel (.462" if my memory is correct). If you do that, then move the flywheel to WOT timing, you'll get another reading on the dial indicator. (.120, or.150, I can't remember) If you then move the dial indicator to each hole in turn, go past TDC to zero it, then move the flywheel to the WOT measurement, and mark it on the flywheel, you'll have a timing mark for each cylinder. Then go through all the cylinders and be sure it's reasonable close to on for each one, and not jumping around. If there's a problem, in order of probability, it could be the trigger, the internal magnets on the flywheel, or the switchbox in question.
When you do any of these things, remove any "advance" modules connected to the switch boxes. In a properly tuned engine, these modules are superfluous anyway. Mine eventually found a home in the chit can.
So, in summary, make sure all the fuel parts are good, and kosher. Check out the freedom of movement of all the linkages. Go through a formal link and sync of timing and carburation. Then to trouble shoot, do the all cylinders timing check and go from there.
hope it helps
John
ps, here's how the 50 MPH bote I bought goes now.
