Where is leaking badly from? 84 was the 1st for the Integrated Tilt-Trim system with everything mounted between the Transom Brackets. I recommend getting a Factory Service Manual
It would be easier to find a used Engine, up to and including1983, with the Trim System, and just transfer over the Parts
If it is on an 80hp, or 85hp 4 cylinder, or the Inline 6, it should fit.
4500-5500rpm is the WOT Range
As mentioned Above, 42mph at 5200 with a bit more Throttle is Meaningless. You/we Need to know what it actually is at WOT.
Is the motor in good Mechanical Shape? Compression numbers, please
Is the Spark properly advance at WOT?
Are the Carbs fully open at WOT?
Is...
110hp will be about 1 mph slower
Regarding the Fishing, if you are fishing just beyond the Dock, even a 20hp would probably be fine. But if you have to get up on Plane to get to the Fishing, then very close to, or the Max would be wise
I suspect an Ignition Issue, due to Heat, possibly Corrosion. Verify that all Connections are clean, and secure. Switchboxes in the 80s Engines were Prone to Failure from Heat.
However, a Fuel Starvation can produce similar Action. A collapsed Primer Bulb happens when the Tank isn't venting...
Looking at the Plugs, I would say the Carbs, need some attention:
Are the Floats set correctly, and not lacking Buoyancy
Are the Metering Jets correct and properly tightened?
Correct Gaskets, O-rings in place?
Is the VRO/MRO Pump working Proplerly?
Is the Enrichment System for Cold Starts...
Plugs look horrible. Running very Rich?
Does the Ignition System produce a Spark that will jump a 3/8" gap for every Cylinder?
Some will say the Compression Numbers are too Low... Might be the Gauge, though.
How long have you owned this Motor?
BTW, the prop is a 17, that stamped Number is...
The Clacking Sound, is the Clutch Dog being 'Eased' into Gear. Causes Severe Wear on the Dog and Gears.
If it were mine, I would be opening the Gearcase up, and inspecting the Parts
In the late 70s we used to "borrow" the neighbours Boat by doing something to get it running without the Key, but we had to wrap a Rope around the Flywheel to start it. Once it was running we could use it. I can't remember if we had Neutral and Reverse, or just Forward.
