2000 75HP Merc 4 Stroke 4 cyl. Carburated WILL NOT START
I have a customers 2000 75 hp Merc 4 Stroke 4 cyl Carburated, he hit something and took the skag and 2 blades off the prop, he got that fixed now it will not start, the carbs have all new kits put in OEM, it has a new stator & ECM Unit & 2 new fuel pumps & filter, new spark plugs. it has good spark and compression, the coils, wires and caps test good by spec, all parts replaced were OEM, it has been sync'd and linked. The timing it right on. The fuel is perfect, it did have water in the inboard tank but we are using our test tank now. The Electric thermo valves are testing good, float level is correct, air screws make no difference where they are it still will not start but if it does it slowly peters out after a few seconds. Can even get it in gear before it quits. I did have it running for 100 yds perfect on the water but it died and now will not start. What are we missing?
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Locate the serial number plate by looking on your motor's transom bracket; the plate will have "Mercury Marine" written on the top. The serial number is the top number on the plate. The number directly beneath this is the year it was manufactured.
The year will be determined by the number of cylinders,,,
A 4 cyl. is a 1986 .
75 - 4 Cyl.
A197882 - B249479 = U.S. Serial Numbers
A70708 = Canadian serial numbers
I had a 1976 15 ft checkmate. Low sides. It was rated at 100 hp. A 100hp in those days was pretty big. My 90 was a 6 cal merc. Todays motors are much smaller for the same ratings. A 75-90 3 cyl should work nicely and be safe.
Most Briggs deco vaves are internal and pretty reliable, the valve clearances are very important, if the exhaust valve clerance is too wide the valve lifter will not work, if there is no adjustment yoy would have to fit a new service valve and re do the clerance by removing material from the valve stem
Your crankshaft turns 2x times the camshaft. Put it this way as # 1 cylinder reaches TDC (top dead center) of the firing/compression stroke, and this will be after a (8 degs BTDC) spark to ignite the air/fuel mix, the # 3 cyl. will be at BDC of the intake stroke and as #1 begins its power down stroke, (during explosion of air/fuel mix), #3 begins its compression up stroke, the #4 cyl. will be coming down with #1 cyl. but #4 will be in the beginning of its intake down stroke, and #2 cyl. will be coming up with #3 but #2will be in its BDC of the exhaust stroke. Which has just fired previously to #1. 1342134213421342 etc.
Now the cam turns to open / close the valves;
In the outline above, #1 cyl. valves will both be closed. #3 cyl. will have the intake starting to close at this point. #4 cyl. will just be starting to open its intake valve, and #2 will be starting to open its exhaust valve. Is all this clear as mud? So as the crank makes one full rotation (in a 4cyl. engine) only the firing of one cylinder has happened.and at every rotation one cyl. will fire. So #1 at TDC then one full rotation, #1 back at TDC, but this TDC is half of its 4 cycles, (1)Intake, (2)compression, (3)power, (4)exhaust. this 1234 refers to the 4 cycles of the rotation not firing order.