Mercury 150 4 stroke (2014) won't turn off after installing new battery.

SOURCE: alarm system

yes
u have to reset it get a new controler

SOURCE: 2003 Saturn Vue Alarm - Ignition Kill

Removing the battery cable is something the alarm companies no the theifs can do. Find the valet button, this along with a few steps that you can find with your alarm manual will reset the system.

SOURCE: Was washing and waxing 1997

put key in door lock,unlock/hold key over windows will go down....then lock/hold key over,windows will go up,press and hold unlock button on remote for 30 secs,you have just reset the alarm/immobiliser.

Testimonial: "Also found out that locking and unlocking the trunk will reset the alarm function. Thank you."

SOURCE: 2001 Jeep Cherokee 4.0 Installed new

Hi. A single click from under the hood on an attempted start could mean a bad starter relay. You may want to test the battery also if there is a charge. Might be the car is not charging the battery.

SOURCE: My 2007 tundra went dead. The ignition won't start

There are several possibilities ranging from a defective starter, to bad cable connections, to the onboard security system locking out the starter relay, or an aftermarket accessory interfering with the starter circuit, or a locked-up/damaged engine.

I have had vehicles towed into my shop for similar complaints when the only problem was that the customer was using a cheap duplicate key that they had made at the hardware store that did not have the required computer chip in it.

I have also had vehicles towed in where the customer had replaced the battery and did not have good cable connections or forgot to connect one of the wires that was supposed to to get hooked-up to the battery connector.

Then there are the questions: Are you getting any kind of "clicking" noises when turning the key or is it completely dead? If it is clicking, WHAT is clicking? Is it the starter motor itself that you hear or just the starter motor relay? Do you have battery power at the starter "S" terminal when turning the key? If not, is the transmission selector in "PARK"? Does the shift indicator on the dash indicate that the transmission range sensor is in "PARK"? (possible defective transmission range sensor) Are there any fault codes stored in ANY of the modules connected to your onboard computer network?

It is really hard to say without being able to see the truck.