On the water we opened the throttle all the way and then turned the
ignition to change the timing, it made a difference but resulted in
the low top speed..

I will get the boat to the dealer but would like to know whats up with
the boat beforehand ..

How fast (roughly) is such a 18.5 boat with 125 HP supposed to go ?

Matt


You should get your linkage fixed first. Ignition advance is a large
part of "throttle" travel on an outboard, and the carbs are timed to the
stator plate or distributor. Typically, the ignition is fully advanced
on larger outboards by mid-throttle, but on this Merc the ignition
advance should pick up the throttle shafts at about 8 degrees BTDC, and
travel with the carbs all the way to 34 degrees BTDC advanced when the
carbs will be wide open.

The engine has to be "running" to do this test with a timing light,
which is hard to do while moving & on the water, so the test must be
done while cranking instead, after the fuel has been run out of the
engine so it does not start.

Just flipping the carbs open at partial advance will not give you full
output.

Also, specs call for "no more than 15 psi variation between cylinders"
on this family of engines. You're in good shape here.

Rob