What's the compression readings?
When you cleaned the carbs, did you make sure the jets were clear and no build up in them?
Where are the air/fuel needles set? should be at 1 turn out, maybe 1 1/8?
If they don't make any difference then the port cover gaskets might be sucking air? Do the...
The backfire could be the gaskets on the port covers have gone bad and
the motors sucking air.
Do the starter fluid test: start motor, spray SF around the intake side of the motor. Any change in the way it runs means it's sucking air.
ONE!!! backfire can blow the port cover gasket/gaskets.
The...
Usually adjustments aren't needed unless someone tinkers or "adjusts" something.
The cables: unless the ends are exposed to the weather then they don't
need lube. The ends or connectors,, you can lube with a couple drops of oil.
Silicone sprays end up getting sticky and can clog.
If you lube...
Backfire/smoke: Could be the system is flooded or there's an air leak somewhere?
Changed floats?? what floats did you change to? Most aftermarket floats won't work and cause flooding.
Load test the battery.
Rebuild the starter, the brush kits are cheap, they sell them here.
You said (the motor sound good for a few seconds and then abruptly stops. It also pops when trying to start.) This sounds like there's an air leak somewhere?
The popping could be the air screws are set wrong or the port cover gaskets are bad and sucking air?
Remove the carbs and check the reeds?
When did they go with stainless bolts?
I've not seen them?
If it started at all I'd say the gasket should be ok???
You do a compression test?
Did it backfire or cough while starting? could be a blown port cover
gasket or 2.
1 backfire can blow the gaskets and hard starting and poor running...
Your not answering all the questions??
(Does the motor continue to rev up after you get to 18mph?
Check / watch the linkage as you have someone push the throttle forward(turn prop as you push throttle, otherwise the linkage binds).
Watch the timer base as you throttle up.) Linkage broken?
How...
More info?
Does the motor continue to rev up after you get to 18mph?
You have Trim@Tilt ?
How big a load are you carrying?
Check / watch the linkage as you have someone push the throttle forward(turn prop as you push throttle, otherwise the linkage binds).
Watch the timer base as you throttle up.
Check for spark??? You try starting fluid?
Clean the plugs or new plugs?
These small motors can get flooded and very hard to start since there's no electric starter.
Every time you pull the cord your adding gas/oil into a cylinder that has a lot of that already in there.
Now that you know the possible year is there any marking ANYWHERE on the motor giving the model or serial#??
On the very
Need a side pic of the lower unit and then the coils and if there's a pack or voltage reg?
If it's not leaking oil, Not sure I'd do anything, same with the pump, the important parts are the impeller, the impellers cup and wear plate, again
not sure I'd do anything??
JB Weld or sillycone.
IF???? there's no gap??? then you missed a nut somewhere???
I'm guessing the middle of the drive a deep hole with a nut way up inside????
Take a pic(might need 2-3 of the bottom side of the cavitation plate showing the screw holes with the fin removed.
