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Appreciate all the help.
OK, so you bought a 1988 140hp, which is a loop scavenged, 90 degree V4, I am assuming it is a 20" model, so it uses the standard V4 gearcase with a different shift rod. This engine uses the conventional integral PTT unit, which is very rugged. Like I say, these engines lack mid range power, so you will want to prop it out as close to 6000RPM as possible. I guess you will want to begin with the conventional stuff, check gear lube and compression. If all seems good, then go ahead and pull the gearcase down for a water pump job and to lube driveshaft splines. The engine has a 9 amp alternator with a water cooled regulator which is under the powerpack (black plastic cover under rear of flywheel). All the electrical connections are under that powerpack cover, and can be real tough to deal with/easy to pinch the wiring, when trying to connect everything with the flywheel still in place. This engine uses both the quikstart and SLOW systems, like on your 70hp. The engine also has the crazy dwell linkage like on your 70hp, but it is adjustable (that dumb looking black plastic knob on stbd side). This engine has four plastic carburetors behind that crazy big ol air box which is attached with many SS bolts. This airbox is an integral part of the air intake system, the engine won’t run as designed without the box, its insert, gasket, and all bolts in place. Each carburetor has two air bleeds, the top is the mid range air bleed, the bottom is the idle air bleed, there are no adjustable needle valves. Keep in mind that this engine induction feeds in an X pattern. In other words, the stbd carburetors feed the port cylinders and visa versa. These engines are very difficult to deal with when idle problems erupt, and they love to spit lean…Don’t even attempt to make any adjustments/assessments running on a flushette, the engine must be run on its boat in the water when trying to deal with idle issues. Trying to make adjustments while running on a flushette will probably cause the engine not to idle at all on the boat in the water. And again, the recirculation system should be checked, which will help idle quality.
These engines use thermostats and a water pressure control valve to control temperature. I’m assuming the original plumbing is still in place on your engine, with hoses running from one head to the other, than on to the water pressure valve on the stbd side. It can be tough to get these engines to heat up at idle with this system, and salt water adds even more problems. The thermostat system can be simplified by simply using parts from later model engines, which eliminates the water control valve, using a big spring behind the thermostat like other conventional OMC engines.
Find an OEM service manual for this engine, don’t try to use the generic fits all books, to avoid excess confusion…..