My engine water temp gauge stopped working last weekend so I replaced it during the week. To my shock when I went out yesterday,the motor was running 165 degrees at idle and 220 at WOT! The old gauge was indicating 145,165. The gauge was installed correctly and the sensor bottomed out in the hole.

The water PSI runs 5 at idle and 15-18 at WOT.Lately I noticed at little steam when I come off plane when the boat settles back down at idle. Did I damage my engine? It seems to be running OK and I had it serviced last summer (new impeller). I am thinking it might be the thermostats. The motor is a 84 2.0 Merc 150.

Any opinions? Should I have the motor checked for damage?

Is the overheat sensor hooked up and working correctly? Has it gone off?

You need to do this:

Run a compression check.

If the thermostants have not been changed lately pull them and check them, or just go ahead and replace them.

You are probably ok, but check it out. Compression should not vary over 10% from each cylinder. If it sits 120+ you should be good to go. If the cylinders are in the 90-100 range it is weak.

I just transferred this motor to a Ranger hull that has a quicksilver box. I am assuming that the alarm is incorporated into the harness. My OB mechanic did the install. The alarm has not gone off. There is no test beep when you turn the key. The compression was 138-144 in 2008.

I am definitely changing out the stats and then see if the temps read normally.

I just transferred this motor to a Ranger hull that has a quicksilver box. I am assuming that the alarm is incorporated into the harness. My OB mechanic did the install. The alarm has not gone off. There is no test beep when you turn the key. The compression was 138-144 in 2008.

I am definitely changing out the stats and then see if the temps read normally.

FYI, I assumed in august of 09 with my Mercury.

Total cost: $5,063.23

Make sure...Or pay the price.

I just transferred this motor to a Ranger hull that has a quicksilver box. I am assuming that the alarm is incorporated into the harness. My OB mechanic did the install. The alarm has not gone off. There is no test beep when you turn the key. The compression was 138-144 in 2008.

I am definitely changing out the stats and then see if the temps read normally.

FYI, I assumed in august of 09 with my Mercury.

Total cost: $5,063.23

Make sure...Or pay the price.

No doubt. One mistake or assumption can be costly. I can change the stats and check the compression myself. How can I test the alarm on the quicksilver controls / ranger boat?

Chech the thermastats,if good your water pump housing could be defective, also make sure your head gaskets ar not blown which could cause a overheating problem at high RPM, and as well your hoses from the thermastats to the motor. I had a motor whith the same problem and it was a blown head gasket then a defective water pump housing that was leaking, and my buddy has a merc 200 that overheated caused from the bypass hose haveing a split in it.

Most of the temp sensors will go off at 190*. When you get over 200* you can start piston damage.

That's why I said you need to check it.

There is also the possibility that the new gauge is defective.

Thanks for your help guys. I am praying that the pistons, rings, and cylinders are OK. I believe that they are because the motor starts, idles, and runs without any hiccups.The compression test should give me the $5K answer though . Is changing head gaskets a big job? It does not look that difficult. I have rebuilt car engines and I have the tools.What are the chances that I warped the head and what will it cost for resurfacing?

No its not that big of a job, just get the proper torque specs and a manual took me about 1 1/2 hours.

If you are not set up to do it just run it by a shop and have them check it out.

I'm betting everything is ok.

Check the impeller. Could be weak.

This is where one of these would be helpful:

http://www.amazon.com/dp/B000O80B5M/ref=asc_df_B000O80B5M1020031?smid=ATVPDKIKX0DER&tag=googlecom09c9-20&linkCode=asn&creative=380341&creativeASIN=B000O80B5M

These have come way down in price over the years and can pinpoint many different engine problems, including hot/cold spots, dead cylinders, etc. If you had one you could confirm if your new gauge was defective or not. I hope you have a bad gauge and have not cooked it.

Thanks for the link / tip.