If that was a gas motor you would have blown a head gasket. That temp can also damage the diesel . Temps should not go above the thermostat setting, no more than 180
Replace the impeller
What you have just makes no since as to why it's happening. If it was the manifold then why doesn't number 6 have same issue. The hoses are routed the same for both manifolds and in most all cases the port side does get a tad bit hotter the the starboard bank.
Scott's idea may provide some...
Welcome
All boats have some sort raw water pump that moves water either thru the motor or thru the heat exchanger. Most likely yours has a belt or crankshaft driven water pump.
In other forums I'm finding the Sherwood G7B pump used...
You have a Weber AFB (also Carter AFB) model 9777s, same as Edelbrock 1410
Rebuild kit numbers are 809064 old and 8M0120193 new. Either number will bring up the kit
From what I've read your good
I wouldn't worry about the PS cooler, it's high on the rear of the motor and will drain automatically. A concern would be IF you have a Bravo outdrive, and if so drain the pump.
You said Carb and 5 plugs (2 block, 2 exhaust) so is the other on the raw water pump?
Don't know which it is so looking at the 10A 2 bank manual, it could be the charger or the Battery. Swap the leads between the Bats and see if it starts flashing on the other one
Manual
As mentioned before, run until the problem starts or at least long enough to be able to start and create a vacuum (if this is the issue).
Stop boat, get your ear close to gas cap and open it, do you hear air being sucked in?
That's about it
Don't know which code number, but you did say sensor reads 198.
If a sensor thinks the something is overheating, it will limit rpm to try and save the motor. This can be a brand new but defective sensor. Can be a bad connection to the sensor, in correct voltage applied to sensors. The scanner...
Injectors are supplied on one side with 12V, the ECM applies a ground to the other side to turn then on/off
With key on, motor off there should be 12V on both sides of the injectors because the ECM is not applying a ground
Saying it will start on starting fluid but not off the gas, then...
