depending on hours 120lbs------165lbs there should not be more than a 5lb difference between cylinders
125 is the least
anything over 100 on all cyl is fine and a good motor
I should be equal on all cylenders and about 110 to 120
Home Depot has a variety of items to choose from to accommodate your needs. The site will allow you to observe and select a particular motor manufactured by Mercury Marine.
I contacted Mercury Marine outboard division and they answered within a week. Very good response.
Mercury wants you to install a battery with at least 525 marine cranking amps if you boat in the summer, and 1000 marine cranking amps for winter boaters.
The water pump impeller on a 7.5 hp Mercury outboard, is located on top of the gearcase, and is driven by the driveshaft.
Mercury Marine uses a lifting eye that threads into the flywheel hub for mounting, and removing, the engine.
Hello.... it appears your outboard is a 1978.
Back in the days of leaded gasoline, readings in excess of 150psi were not unusual. Later models run in the 120 - 135 range, although the engine will run on around 90 - 100psi. The key thing here is that you get close to the same reading on all cylinders, no more than 10 - 15 psi difference between the lowest, and highest readings.
the lower compression of the marine pistons will alow you to cram more air and fuel into your motor, the disadvantages are harder starts in the cold and maybe some drivability issues.
difference of motor and marine insurance