Clams Canino
06-14-2002, 09:44 AM
Lets go to the very beginning of the cylinder Merc project. Behind Kiekhaefer's back, chief engineer C. D. Strang started development of the inline 6 as secret project. Three 2 cylinder crankshafts were welded together and two 4 cylinder blocks had one cylinder sawed off and were welded together. A six cylinder car distributer was grafted on in place of the magneto and a new motor was born. During development it was always covered or hidden whenever Carl was around. After it had been tested and adjusted, they called Kiekhaefer down to the dock and pulled a blanket off of the prototype. At first Kiekhaefer laughed out loud!! When he was done laughing they convinced him to take it for a test run.....when he returned to the dock he is reputed to have said "It speaks with authority. Build it."
The production motor was ready for the 1957 model year.
This first version, the "Mark75", got 60 hp from its 60 cubic inches. To tell these powerheads from other similar Mercs the name "Marathon Six" is cast in on the fuel pump side. This motor is based very heavily on the 2 and 4 cylinder motors from which it was derived.....10 ci per cylinder and one 3/4" Tillotson AJ series carb per pair of cylinders feeding the Kiekhaefer internal reed valves. Even though there are 3 fuel pump pads, only 2 are used. The two pumps are piped in series to give greater suction/lift capability to the pump system to lift fuel from remote tanks low in the boat. Ignition came from a special 6 cylinder distirbutor that over comes what would be the normal limitiaitons of a 2 stroke 6 cylinder distributer by actually being two 3 cylinder ignitions incorporated in unision. 2 coils, 2 ballast resistors, 2 sets of points, one distributor. Inside the distributor, on the rotor button, there are 2 contacts that meet the spark plug contacts. One feeds from the bottom center coil brush in the normal way, the other from an insulated slip ring on the side. Each feeds only 3 cylinders because of the way the points trigger the coils. The firing order is 1-6-4-2-5-3. Back in the 50s lower unit technology wasn't yet developed to handle the power of such an outboard, so Kiekhaefer simply followed the example of some other steam drive and marine drive propulsion systems and set up the now famous "Direct Reverse" system. With this system the lower unit gears stay engaged all the time. Reverse is achieved by starting and running the motor counter clockwise instead of the normal clockwise. At the helm a special control box controls the throttle and selects which direction the motor will start and run. The throttle handle moves through a Z shaped gate and actuates an array of micro switches to stop the motor and allow starting in the desired rotation. On the top of the handle is a button that you press with your thumb to actuate the starter motor itself. The "pistol grip" shaped handle and thumb button strongly resemble a World War II fighter plane control stick and machine gun actuator....great symbols of power in 1957. There are 4 special parts on the motor for the Direct Reverse system. First and most obvious is the special starter. This big clunky thing has 2 drive gears. At rest one is in the normal position below the starter ring gear on the flywheel, the other is on the extended end of the starter shaft above the starter ring gear. The starter also has 2 solenoids. For forward one solenoid engages the starter motor to run counter clockwise...the lower drive gear runs up its spiral ramp and engages the flywheel gear turning the crankshaft clockwise. For reverse the other solenoid engages the starter motor to run clockwise and the upper drive gear runs down its spiral ramp to engage the flywheeel gear and turn the crankshaft counter clockwise. The motor's second special part is throttle linkage that pushes the carbs OPEN at both extremes of the throttle cable's throw. This is necessary to increase motor speed as one pulls the pistol grip throttle farther back to go faster in reverse as well as the normal throttle opening for forward. Special part number 3 is the Direct Reverse water pump. Regardless of which way the motor runs water must be pumped up to the powerhead. This is achieved with a water pump with two check valves. Each check valve is located a few degrees off of the water pump's "tight" side where the water is squeezed out of the pocket. The simple rubber check valve allows water to exit the chamber from whichever side it is being squeezed and not back down (into the pump) on the side where the impellor is opening the pocket to draw water in. OK so now you are wondering what special part #4 is.....
In the distributor there must be some mechanism to throw the ignition to the other side of TDC to compensate for "BEFORE" and "AFTER" TDC changing places. This is achieved with slack in the distributor drive shaft. The upper part of the distributor shaft that is driven by the distributor drive pulley is not the same piece as the shaft with the cams for the points and the rotor button. The coupling between these 2 shafts has quite a bit of slack. This allows the timing slip over to the other side of top.
GAP TO BE FILLED HERE
"Turning the corner from the 50's to 1960 brought the end of the "Mark" designations as well as the loss of the 60hp Mark 75 Marathon Six. 1960 however, heralded the introduction of the brand new 76ci powerhead. For 1960 the 66ci Mark78A was retained as the Merc 700 and the new 76ci powerhead was designated the Merc 800. The new 76ci powerhead also received a new firing order to reflect the change in exhaust tuning mentality from “three twins” to “two triples”. This new firing order is 1-4-5-2-3-6.
In 1960 both of these engines were only available in direct reverse configurations. In 1961 the same two blocks were back with the welcome addition of of full gear shift lower units. 1961 is the only year that both Direct Reverse and Full Gear Shift were simultainiously available. This came about as Kiekhaefer was adamant about not wanting to put FGS lower units on the Inline Six’s for fear of reliability issues with the extra power. Enter again Charlie Strang with yet another project behind Carl’s back. Only when he had the unit perfected did he let Big Carl in on the project. Carl finally relented to offer FGS on the Inline Six’s so long as the Direct Reverse was also offered. Overwhelming public responce to the FGS models signaled the end of the line for the Direct Reverse "Dockbuster" lower units. From 1962 forward Inline Six motors were only offered in FGS configuration.
A cosmetic note is that 1960 and 1961 uniquely featured chrome MERCURY lettering on the top cowling in place of the previous red or blue decals. Different letters were used for the left and right sides and they are not interchangeable. (there is also a rumor that the 700 and 800 has different *size* letters - please confirm someone?)
1962 was another year of big advancement. Introduced in 1962 was the new "Powerdome" combustion chamber, as well as the introduction of a new 89ci powerhead. The "Powerdome" combustion chamber puts the combustion chamber center more over the top flat land of the piston and I think it fills in some of the dead space shielded from the flame front by the deflector dam of the piston. Racers had been filling in this space with welded in "pads". Compression is increased, turbulence increases, dead "end gas" area decreases, decreasing the octane demand over a similar combustion chamber. Externally Powerdome spark plugs sit off center of the crankshaft and bores, earlier non Powerdome heads have the spark plugs on center with the bores and crank. The 76ci powerhead got the Powerdome combustion chamber (and sporting an extra 5 horsepower) was upgraded from the 61 Merc 800 to the 62 Merc 850.
The venerable 66ci powerhead got to live one final year as the 1962 Merc 700. The 62 Merc 700 us unique in this respect: Except for the 62 70 hp full gearshift all 60 and 66 ci motors use the smaller spline used on the 40 and 44 ci motors. All 76ci and larger use the same larger splines. What this means: if you want to jam an old 60 or 66 ci motor on a later driveshaft you need a 62FGS 70hp or 76ci 80/85 hp crank for bolt up only type work. Reverse would also work; if you found a Mk75 or Mk78 Merc 600/700 DR LU and have only a 76ci DR or 76 or 66 FGS motor you need the smaller spline crank from the old motor for work that doesn't require welding. Conversely though, from the 76ci motor forward. you can indeed use a lower unit/driveshaft of equel or later vintage as a bolt on proposition. The length of the shift-shaft changed over time, as did the locating pins, but a lower unit from a 1988 Merc 1150 will indeed bolt on to a 1961 Merc 800 FGS leg and work.
The real news however in 1962 was the all new 89ci powerhead in the new Merc 1000 "Phantom" becoming the first production outboard to break the 100hp barrier.
This engine was the first of the Inline Six's to be painted black, with the rest of the line to follow. To this day Mercury Black is properly designated "Phantom Black". This time it was Charlie Strang’s mother who came up with the idea in response to the problem that the motors had grown so much that they were beginning to look unwieldy. “Well, a large woman always wears a black dress. Why don’t you paint it black?” Again Charlie set up a surprise viewing for E.C.K. When Carl saw the A-B comparison he said: “MY GOD! Let’s paint them ALL black!” And so began the end of the "White Mercs" Also, the chrome MERCURY letters on the top cowl vanished in favor of a large decal on the wraparound. A new diode rectifier replaced the previous selinium plate models and there were significant changes to the starting solenoid and ignition coil resister / ballast system. (though the distributor and fireing order stayed the same as the 76ci Merc 800/850.)
The production motor was ready for the 1957 model year.
This first version, the "Mark75", got 60 hp from its 60 cubic inches. To tell these powerheads from other similar Mercs the name "Marathon Six" is cast in on the fuel pump side. This motor is based very heavily on the 2 and 4 cylinder motors from which it was derived.....10 ci per cylinder and one 3/4" Tillotson AJ series carb per pair of cylinders feeding the Kiekhaefer internal reed valves. Even though there are 3 fuel pump pads, only 2 are used. The two pumps are piped in series to give greater suction/lift capability to the pump system to lift fuel from remote tanks low in the boat. Ignition came from a special 6 cylinder distirbutor that over comes what would be the normal limitiaitons of a 2 stroke 6 cylinder distributer by actually being two 3 cylinder ignitions incorporated in unision. 2 coils, 2 ballast resistors, 2 sets of points, one distributor. Inside the distributor, on the rotor button, there are 2 contacts that meet the spark plug contacts. One feeds from the bottom center coil brush in the normal way, the other from an insulated slip ring on the side. Each feeds only 3 cylinders because of the way the points trigger the coils. The firing order is 1-6-4-2-5-3. Back in the 50s lower unit technology wasn't yet developed to handle the power of such an outboard, so Kiekhaefer simply followed the example of some other steam drive and marine drive propulsion systems and set up the now famous "Direct Reverse" system. With this system the lower unit gears stay engaged all the time. Reverse is achieved by starting and running the motor counter clockwise instead of the normal clockwise. At the helm a special control box controls the throttle and selects which direction the motor will start and run. The throttle handle moves through a Z shaped gate and actuates an array of micro switches to stop the motor and allow starting in the desired rotation. On the top of the handle is a button that you press with your thumb to actuate the starter motor itself. The "pistol grip" shaped handle and thumb button strongly resemble a World War II fighter plane control stick and machine gun actuator....great symbols of power in 1957. There are 4 special parts on the motor for the Direct Reverse system. First and most obvious is the special starter. This big clunky thing has 2 drive gears. At rest one is in the normal position below the starter ring gear on the flywheel, the other is on the extended end of the starter shaft above the starter ring gear. The starter also has 2 solenoids. For forward one solenoid engages the starter motor to run counter clockwise...the lower drive gear runs up its spiral ramp and engages the flywheel gear turning the crankshaft clockwise. For reverse the other solenoid engages the starter motor to run clockwise and the upper drive gear runs down its spiral ramp to engage the flywheeel gear and turn the crankshaft counter clockwise. The motor's second special part is throttle linkage that pushes the carbs OPEN at both extremes of the throttle cable's throw. This is necessary to increase motor speed as one pulls the pistol grip throttle farther back to go faster in reverse as well as the normal throttle opening for forward. Special part number 3 is the Direct Reverse water pump. Regardless of which way the motor runs water must be pumped up to the powerhead. This is achieved with a water pump with two check valves. Each check valve is located a few degrees off of the water pump's "tight" side where the water is squeezed out of the pocket. The simple rubber check valve allows water to exit the chamber from whichever side it is being squeezed and not back down (into the pump) on the side where the impellor is opening the pocket to draw water in. OK so now you are wondering what special part #4 is.....
In the distributor there must be some mechanism to throw the ignition to the other side of TDC to compensate for "BEFORE" and "AFTER" TDC changing places. This is achieved with slack in the distributor drive shaft. The upper part of the distributor shaft that is driven by the distributor drive pulley is not the same piece as the shaft with the cams for the points and the rotor button. The coupling between these 2 shafts has quite a bit of slack. This allows the timing slip over to the other side of top.
GAP TO BE FILLED HERE
"Turning the corner from the 50's to 1960 brought the end of the "Mark" designations as well as the loss of the 60hp Mark 75 Marathon Six. 1960 however, heralded the introduction of the brand new 76ci powerhead. For 1960 the 66ci Mark78A was retained as the Merc 700 and the new 76ci powerhead was designated the Merc 800. The new 76ci powerhead also received a new firing order to reflect the change in exhaust tuning mentality from “three twins” to “two triples”. This new firing order is 1-4-5-2-3-6.
In 1960 both of these engines were only available in direct reverse configurations. In 1961 the same two blocks were back with the welcome addition of of full gear shift lower units. 1961 is the only year that both Direct Reverse and Full Gear Shift were simultainiously available. This came about as Kiekhaefer was adamant about not wanting to put FGS lower units on the Inline Six’s for fear of reliability issues with the extra power. Enter again Charlie Strang with yet another project behind Carl’s back. Only when he had the unit perfected did he let Big Carl in on the project. Carl finally relented to offer FGS on the Inline Six’s so long as the Direct Reverse was also offered. Overwhelming public responce to the FGS models signaled the end of the line for the Direct Reverse "Dockbuster" lower units. From 1962 forward Inline Six motors were only offered in FGS configuration.
A cosmetic note is that 1960 and 1961 uniquely featured chrome MERCURY lettering on the top cowling in place of the previous red or blue decals. Different letters were used for the left and right sides and they are not interchangeable. (there is also a rumor that the 700 and 800 has different *size* letters - please confirm someone?)
1962 was another year of big advancement. Introduced in 1962 was the new "Powerdome" combustion chamber, as well as the introduction of a new 89ci powerhead. The "Powerdome" combustion chamber puts the combustion chamber center more over the top flat land of the piston and I think it fills in some of the dead space shielded from the flame front by the deflector dam of the piston. Racers had been filling in this space with welded in "pads". Compression is increased, turbulence increases, dead "end gas" area decreases, decreasing the octane demand over a similar combustion chamber. Externally Powerdome spark plugs sit off center of the crankshaft and bores, earlier non Powerdome heads have the spark plugs on center with the bores and crank. The 76ci powerhead got the Powerdome combustion chamber (and sporting an extra 5 horsepower) was upgraded from the 61 Merc 800 to the 62 Merc 850.
The venerable 66ci powerhead got to live one final year as the 1962 Merc 700. The 62 Merc 700 us unique in this respect: Except for the 62 70 hp full gearshift all 60 and 66 ci motors use the smaller spline used on the 40 and 44 ci motors. All 76ci and larger use the same larger splines. What this means: if you want to jam an old 60 or 66 ci motor on a later driveshaft you need a 62FGS 70hp or 76ci 80/85 hp crank for bolt up only type work. Reverse would also work; if you found a Mk75 or Mk78 Merc 600/700 DR LU and have only a 76ci DR or 76 or 66 FGS motor you need the smaller spline crank from the old motor for work that doesn't require welding. Conversely though, from the 76ci motor forward. you can indeed use a lower unit/driveshaft of equel or later vintage as a bolt on proposition. The length of the shift-shaft changed over time, as did the locating pins, but a lower unit from a 1988 Merc 1150 will indeed bolt on to a 1961 Merc 800 FGS leg and work.
The real news however in 1962 was the all new 89ci powerhead in the new Merc 1000 "Phantom" becoming the first production outboard to break the 100hp barrier.
This engine was the first of the Inline Six's to be painted black, with the rest of the line to follow. To this day Mercury Black is properly designated "Phantom Black". This time it was Charlie Strang’s mother who came up with the idea in response to the problem that the motors had grown so much that they were beginning to look unwieldy. “Well, a large woman always wears a black dress. Why don’t you paint it black?” Again Charlie set up a surprise viewing for E.C.K. When Carl saw the A-B comparison he said: “MY GOD! Let’s paint them ALL black!” And so began the end of the "White Mercs" Also, the chrome MERCURY letters on the top cowl vanished in favor of a large decal on the wraparound. A new diode rectifier replaced the previous selinium plate models and there were significant changes to the starting solenoid and ignition coil resister / ballast system. (though the distributor and fireing order stayed the same as the 76ci Merc 800/850.)