General
The 60 horsepower Mercury four stroke was introduced some time around 2001. Besides covers, bracketry, electrical and fuel delivery, the design has been consistent through 2019. From Mercury Marine‘s site:
- 2.56″ bore x 2.95″ stroke, inline 4 cylinder, 60.8 cubic inches
- 2 valves per cylinder, overhead camshaft
- 20″ or 25″ shaft, (15″ Formula Race model only)
- 1.83:1 standard ratio, 2.33:1 Command Thrust
- 247 pounds at lightest factory configuration
- 13 spline prop shaft (same as previous non Big Foot 40-60HP 2 stroke models)
Other useful facts
Crankcase oil is stored in the midsection.
Ignition
Carbureted models used two coils in a wasted spark configuration. EFI models went to a coil on plug configuration initially (4 coils) and then switched back to a 2 coil configuration sometime around 2012.
The crankshaft position is measured by a variable reluctance (VR) sensor triggered off of the toothed ring (tone ring) that is molded into the flywheel. The tone ring is located about an inch above the starter teeth. Three different flywheels came on these motors. Earlier models had fewer tone ring teeth, approximately 25. At some point, they switched to a 60-6 tooth tone ring. Newer models (1C104424 and Up, the same time they switched back to a 2 coil configuration) call for a different flywheel part number. Although it doesn’t appear to be drastically different in pictures, part interchangeability isn’t guaranteed.
Fuel Delivery
Presumably, the carbureted models could be converted to EFI with aftermarket fuel injection with about the same difficulty as converting OEM EFI to aftermarket fuel/spark control. Until certain, we won’t talk about it.
In EFI models, fuel is pumped from the fuel tank by a low pressure fuel pump and then fed to the high pressure pump. The high pressure fuel is internally regulated within the vapor separator (huge aluminum canister above the oil filter).
The low pressure pump is mounted onto the valve cover and is driven off of one of the cam followers. The hose running straight through is water and used cool the pump.
The high pressure pump is powered via the yellow plug in the top of the vapor separator. Water runs through the black block to the left of the vapor separator to cool the bypassed fuel. Fuel is fed to the round distribution block from the vapor separator and then to the fuel injectors.
The fuel injectors are low impedance so they’re easily driven by modern fuel injection controllers.
The throttle body can be seen in the photo above. The throttle position sensor and throttle linkage are both visible. The Idle Air Control Valve (IAC) on these motors is obnoxiously loud. The motor is quieter and idles lower if the IAC port on the valve is plugged. Perhaps they addressed the problem in the newer motors.
Cylinder Head, Camshaft and Oil Pump
The camshaft is driven by the cogged pulley on the top of the cylinder head. The lobes have 170 degrees of duration at .050″ lift and 220 deg @ .005″. The total valve lift is .318″ at both valves.
The oil pump is a gerotor type and resides in the bare aluminum housing at the opposite end of the cylinder head from the drive pulley.
The combustion chamber is hemispherical in that the valve axes are not parallel. The exhaust port feeds exhaust gas into the cylinder block where it is cooled by an adjacent chamber of raw water. The exhaust is then fed through the mid and out through the lower unit.
The intake ports are just shy of 1.25″ diameter and, based on the displacement, should support a peak torque around 7000 rpm. The intake and exhaust ports both make a 180 degree turn so port modification would be arduous. Fortunately, they are well formed from the factory and don’t have any sharp edges or turns.
Valves removed and cleaned. American Quarter for size reference. 
Exhaust port back lit. Dimple in runner visible in lower right hand corner of exhaust port. 
Intake port back lit. 
Exhaust runners cleaned in preparation for port holing. 
Non serviceable cam bearing surface. Slight wear visible.
Short Block
The block is an open deck design in that the cylinders are not constrained by the block where they meet the cylinder head. The cylinder walls are pressed in steel sleeves.
The main caps are integral to the oil pan. Although oil pan is a misnomer in this case since the oil is stored in the midsection of the motor. The small end of the rods are floating and rotate on a superfinished surface, not a bronze bushing. The crank shaft is in the conventional four cylinder configuration where the inner two pistons and the outer two pistons are at the same vertical location. The crank drive shaft splines are larger than those used on the 40-60 HP 2 stroke motors.
There is a removable cover over the water ports that cool the exhaust gasses. The cover houses the coolant temperature and also has an access hole to the exhaust. The exhaust hole would be ideal for an O2 sensor.
Cowling and Midsection Covers
During the renovation of 2012, Mercury changed the cowlings from fiberglass to plastic and improved the design of the covers that go over the midsection.
