Not an OB guy but an alarm is going off non-stop but sensors are unplugged, how does that happen?
If its not overheating then it may just be an issue with the alarm and not the motor. Do find out if it is doing something to cause an alarm
Is there any difference in RPM between motors when trying to get on plane?
One chip will not cause what your seeing
The fuel is old and seafoam is crap IMO and cannot make bad gas into good gas. If the gas is bad, there is no fixing, it has to be used up and new added or you just have more...
So far not sounding like an issue at all.
The thermostat will not open until its at least 140* and your saying it stays 150-160. The hem gauges are not normally real accurate and can vary +/- at least 10*
Your plugs look fine
Crank it over a few times then put old or new plugs in and see if it will start.
If it starts and runs ok, check your exhaust manifolds to see if there is a leak and it gets hydrolocked
Stop making new threads for same problem
There is a fitting on top the drive that the raw water hose connects to. This fitting can get clogged up. Remove it and see if that is the issue
For a 5.0 it's part number 21951348
https://www.volvopentastore.com/Maintenance-Parts-5-0l-5-7l/dm/cart_id.069313114--session_id.048509256--store_id.366--view_id.787187
Don't go there, will be a long con-vo
The brass fitting that screws into the block is the standard 1/4 NPT. The NPT changes it to the Merc thread which uses the Blue plug or Hradin Marine SS plug
Motor came out today
This is new, a tray under the intake. Have not seen that before, guess we will install in rebuilt motor. Injectors go out tomorrow to Smitty's in Michigan
Using your part number "YSC10103100C" the part comes up at a few different places. Are you looking for a cheaper place or any place? If cheaper I cannot help