Howdy, need some help troubleshooting

So I bought a Ranger 518 VX. It has a 1999 Johnson 200 on it. I ran it on clappers at my house and everything seemed to be fine, but I found an issue when I took it out to the lake this weekend. It was pissing water like it was supposed to, but the gauge was showing no water pressure. My buddy said there must be something wrong with the gauge as it was possing water. After driving around on the lake for a little while, the hot light came on. I immediately turned off the engine and let it cool down. While waiting I looked in the rubber grommet in the rear that the motor pisses water out of was torn all around the threaded insert. I drove back to my trailer and loaded it up with no issues and have ordered the replacement rubber grommet. I also put my air compressor on the line going to the gauge from the engine and verified that the gauge is working. I can't see that grommet letting extra water out cause the engine to overheat and that doesn't really explain the lack of water pressure on the gauge. Does this mean I need a new water pump or water pump impeller or new thermostats? I've only really ever worked on inboards or inboard outboard with cloaed cooling systems so this is a little foreign to me. Thank you for your help!

Ps while the engine was cooling down I caught my first bass so the day was definitely a success!

Looks like you bought some ones problems. I see this over and over. People buying boats without test running on the lake and not having them checked out. I tell all boat buyers to talk to his or her boat mechanic. First off you should have your location in your sig. That motor when all is well the stream will almost sting your hand. If not it needs a new complete water pump. I would do a complete cooling system service. Did you get any service records because this motor may need a lot more than that. That motor needs the VRO pump changed periodically, check the lower unit oil for water contamination. The main shaft seal is bad to start leaking on this motor. Time to change the seals is when your changing the water pump as the seals are under the water pump. Fuel lines may need replaced. Could need a de-carb and new Champion sparkplugs. On and on.

Most likely the impeller is bad. We see boats come in everyday that is over heating and it is still peeing water with a good enough stream that would appear to be sufficient flow. But sometimes its more about volume and not pressure. It also could be that some of the fins have separated from the impeller and are stopping up the discharge tube. It could be a number of causes. The best thing to do before throwing parts at it is take it to a qualified repair shop and have it looked at. If you need any help, I am the service manager at North Texas Marine and would be glad to help. We are open Tue-Sat and you can always feel free to call me at 940-665-9331.

Thank you both for the responses.

Gary, the boat was bought from a long time friend, I have been fishing on it many many times before over the years. I do have all the service records, and it has been maintained very well until two years ago when it was put up due to some personal issues. The fact that there are some problems are no surprise to me, that is what happens when things, especially boats, sit. Lets just say I got a good enough deal on the boat to be willing to mess with the problems. I will make sure and update my signature... I thought I had done that quite some time ago when I joined. I already changed all the plugs, cleaned out the fuel system, changed all the oil, and looked at all of the fuel lines, and various hoses under the cover for dry rot. I work on cars quite a bit so I have the basics down pretty good. I will definitely look at the VRO pump as well, I was unaware that was an issue on these engines, but then again, I know nothing about them.

BoatRx. That's a clever username. I am down in Houston, so unfortunately you are no where near me, but I definitely appreciate the advice. I will try to find someone local that can look at the engine for me. Thank you very much for the advice!

No problem. There are plenty of qualified shops in Houston that can help. Its always a great idea to have the service records available when you change shops so that if they are needed the tech would have access to those. Again, good luck and tight lines!

I can recommend Strack's in Spring Tx. I sold an old Ranger to a friend because no one could fix the engine. Took this guy 2 days and it runs better that it has before. Give them a call 281-353-7075.