To start at the end, alphas click when the prop is turned and they are
in gear. That's the gears skipping. Alphas use the input torque from
the engine to hold the gears in mesh. When you apply pressure from the
prop the beveling on the gears works the opposite way and forces them
apart. Completely normal.

A crack in your cap means replace it. Not epoxy. If the wires are old
replace them too. When you say magnetic points you mean it has the
merc thunderbolt ignition? It does seem like an ignition problem.
Does the ignition advance when you watch it with a timing light while
someone revs the engine? You should be able to see the mark swing away
with the light. Look down the carb throat with the engine off and make
sure you are getting a good squirt of gas from the accelerator pump
when someone moves the throttle.

Paul wrote:
Hi All,

This is a 4.3 V6 Merc newly rebuilt. EST, magnetic points. Boat is 19
ft B/R with 19P Laser II prop.
Idles OK, goes to 2000 rpm and that's all. When trying to accelerate
above that it backfires and stumbles, rpm drop to below 1500. You back
the throttle off and it speeds up (but not above 2000 rpm). It won't
plane.
Pushing the throttle all the way will cause carb and exhaust backfire
and stumble with rpm drop but it won't die (accelerates and decelerates
on its own erratically).
Wires are OEM Merc old but seem good, distr. cap had a tiny (!) crack
(from constant manipulation) on the outside of no.1 collar but I
covered it with lots of epoxy (no.1 fires OK). Timing 4-8 deg. before
TDC (not much change). Idle at 550 is OK up to 2000 in neutral (never
tried above unless in gear). Problem appears at higher rpm. Don't wont
to kill freshly rebuilt engine...

How to test all ignition components? Could this be fuel starvation
(pump or fuel tank vent)?

Any ideas?


I also have slight clicking when turning prop dry (especially forward),
less loud in reverse (sounds like lower unit ...) Much louder in the
water though (knocking - ticking) when in gear. Could this be
maladjusted linkage? Oil level was OK when checked last time (not
recently). Any reason to be worried?