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As stated before the motor needs" Compression, in both the Combustion Chamber, and in the case of a 2 Stroke, in the Crankcase. Air-Fuel delivered to the Combustion Chamber, via the Crankcase. A Source of ignition at the proper Time

Evans lost to GM in the Courts. About 100 yrs ago, GM reversed engineered the Combustion enough to recreate the the turbulence, and not infringe on Ricardo's Patent, which was issued in the 1920s. Also the Ricardo patent was for Flathead Heads, GM's design was for an OHV engine, thus...

Maybe. Put you hand over the carb, blocking it completely, open the carb fully and have someone spin the flywheel. Do you feel any suction? If not, the gasket between the carb and block may be bad, the crankcase might not sealed, or the Reeds are bad. If you feel Pressure, the Reeds are...

I too recommend rebuilding the OEM Carb, using a Mercruiser Rebuild Kit. You say the previous rebuild didn't restore its performance, all I can say, is you didn't clean all the fuel delivery circuits, adjust all the linkages that could have been affected by slightly different gaskets on between...

Sad to hear that I was correct

That is a completely different engine, than what a 1994 engine would be.

There are a few more contributors on iboats that have access to MercNet. However, being it proprietary, they are limited to what they can openly reveal.

A 3/8" Gap is for testing the Ignition System's capacity to supply a Spark strong enough to jump a gap of 0.030" when the Spark Plug is subjected to the Conditions inside the Combustion Chamber on the Compression Stroke Something has happened to cause a loss of more than 50% of the Engine's Rpm...

High Humidity, which can happen when it rains, can wreck Havoc on Plug Wires. It can also help create conductive Paths on the Ceramic Insulator of the Spark Plug, especially if that Insulator is cracked Outboards can be just as finicky, the newer ones, with all the Electronics, even more so

What was approx 3/8" gap? A regular spark plug has a gap of 0.030", 3/8" is 0.375", almost 13 times wider

All the Cylinders getting fuel? If not, they aren't getting Oil. What do the Plugs look like? As for Good Spark, is it good enough to jump a 3/8" gap? Have you tested the Compression?

However since you don't know the Service-Repair History, what is the Gear Ratio of the Outdrive currently on the Hull? What is the Manifold Vacuum at Idle, and at WOT, read from an actual Vacuum Gauge? I know on my 5.7 it is 18" at Idle, and 4.5" at WOT with the 500cfm 2bbl, and with the...

An Unregulated Charging System hitting 16 volts in pretty much normal at high Rpms. Those charging systems don't put out much Current, and simply use the Battery(Wet Cell ONLY), as a sacrificial Reservoir, boiling when the Voltage is high. After the drain on the battery, from cranking, and use...

Low vacuum, as well as an Inverted Vacuum curve, I would be inclined to think the Sensor that monitors it defective. In Post #24 you said the Boat-motor was new to you, so you haven't got the repair History of it. I assume this below the WOT range of this motor, rpm you posted is how it has...

How long have you owned this Boat and Motor? Before this low rpm issue came about, what Rpm was it getting at WOT?

Idle speed is set in Gear, under load, and is generally 600rpm, give or take 50rpm. 1100 in Neutral, will do a lot of Damage to the Clutch Dog, and Gears. Do you have the correct Factory Service Manual for the Motor? If not, get one. It will have the correct Specs and the process of the Link...

Those POS, are also for pushing the Bow Down Here are some general suggestions as to what Height the Engine should be mounted. Choice of Prop, is also a factor as to how high it can be raised. That said, Heights higher than Flush with the Hull, only start to offer benefits above 45-50mph

Cable may need replacing. In the 60s the Cable Ends could be tightened when they got loose. I don't know if the Silver Item, between the Thumb and finger is actually Screw

Air-Fuel, Compression, and Spark at the proper time and it should fire. You have fuel, in the cylinder What are the Compression Numbers?(this is a very long thread) You have Spark at the Plug Wire The chances of both Plugs being bad is unlikely Maybe the Spark Timing is was off Maybe there is...

It appears to be functioning, but once it warms up, it could become unstable.