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Start by checking your batteries. A fully changed Bat will read 12.6 to 12.7V.
If the Bat reads much lower then that it could be it has a shorted cell
If Bats read good then it is probably the charger
Merc makes one but they kind of high 91-18078 but it's designed to use the hand held vacuum fuel pump tester
But could also get some 3/8 gas line, a plastic Tee and some hose clamps.
At max of 10 psi, line and hose claps will work. Most auto parts places will have a straight or elbow fitting...
The tube should go to the air pump on top the motor next to the thermostat housing. The tube connects to the air pump to purge water out during winterization
Many have had cracked housings and the biggest reason is are draining with pump the drain plug is reinstalled. Later there is a small...
The new motors have 12V stay alive power with fuses coming from the Bats. Might be a loose connection on the small wires or even a fuse not fully plugged in. Look for the fuses/wires at the Bats
Without a wiring diagram we're going to be guessing. Going to see if I can find find a diagram. Can you post some pics of the master key and helm switches?
I've driven one of your type but never got into the wiring. There is a main switch in the cabin which when turned ON it supplies power to the toggle switches at the helm. If power comes from the key or the cabin it comes in on the Red/Purple to your switches
The ON/OFF at the helm should have...
Sounds like the float is stuck
Could get another pump and float (or all in one unit) and attach to a piece of aluminum flat stock. Bend the stock so it can be slid under the motor and attached to the stringer. This way it doesn't have to be removed
No clue, if ya remember I had one of the 3 wire ones on the HP transom assembly. Added the digital to analog converter just like it said and it never worked
Hope you have better luck
Looks are ok, but are they flat?
Take a framing square or other steel ruler and suck and see if they are flat. Might need to put a flat file across them to true them up
Being CATs there will be exhaust bank O2's as you mentioned.
The injectors need to be tested by someone that knows how to test. If they go to a auto place they may not test them at high rpm over time and high flow.
The best guy I know is an OSO member that goes by ArticFriends (Smitty). Or...
From what I find about the GXI is it does Batch firing of the injectors and has a single fuel rail. Don't see how a scanner can do a misfire or tell which bank has more or less fuel. Motors like the 8.1 can because individual coils and injector control
With the motor getting worst the more it...
While the drawing is a bit messy looking I think I'm understanding what your wanting to do. Looks like most are lights and with that all the grounds could be tied together and run separate hots to each (except red/green)
My rule of thumb has always been 2 pitch up from 4 to 3 blade, or 2 pitch down from 3 to 4 blade.
My motors are 250HP each and they should be able to reach 6K RPM but have had them a bit over 5K just for a few seconds but didn't want to push it just yet. There is plenty of power, I can be...
