Temp guage reads HOT

I recently had some work done on my 2002 Outback. I had a stereo installed in the dash and a depth finder installed in the dash. Both work fine.

However, when I launched boat for the first time after the install, i saw that my temp guage began to spike after a few minutes of running the boat.

I raised the engine box while idling and the block seemed cool/slightly warm to the touch (not 230 degress that the guage was indicating).

As a percaution, i asked a marine mechanic to take a ride with me to see if he felt the guage was reading accurately.

He ran the boat at 4000 rpm and the guage spiked again and would then bounce between 190 and 235 degress within seconds.

He also touched the engine and thought things were fine, but cautioned me that he was an I/O specialist not an inboard specialist. He said maybe its a thermostat problem.

The boat has been running well.

My question is:

Is it possible that the installed items in the dash are shorting out the temp guage making it bounce around?

Is it possible for me ( a B minus handman) to install a new thermostat myself?

Or is this something serious where I shouldnt run the boat until I get it properly diagnosed?

Thanks.

The engine is a 315hp carb.

I'd definitely check the wiring to the heat gauge to make sure they didn't knock anything loose. I'd also make sure there aren't any other problems in the cooling system just in case it's not the gauge. The easiest thing to check would be the impeller. I'd also make sure there are no blockages in the water pickup and I'd also check the water strainer where the transmission cooling lines run into the water line just to make sure that you didn't suck up anything that is causing a partial blockage. Changing the thermostat is also easy enough and it may be a good precautionary thing to do instead of having it lock shut later on the water.

To me it actually sounds electrical in nature, but if it was my boat I'd go through all the checks just to eliminate the chances of having it overheat for real and cause damage.

I would go through lowdrags steps first. Then, verify the ground connection on the backside of the gauge. When lyeing on your back, looking up at the gauge, verify that it is on your right hand mounting post of the gauge, if it is not, put it there. Brian Raymond

barefooter i just went thru something similar a few weeks ago.lowdrag gave great ideas to you pretty much the same brian recommended for my 02 ls. turned out to be my tstat.very simple to replace. do check you tran filter,replace you impellar a real good measure if you over 100 hrs and the tstat is 3 bolts 1 gasket mine(310hp carb) and pulling one hose off for ease of work.also dont forget to check wiring at the battery and any new connections for a loose ground .

Thanks much for the helpful posts....It really helps to have some outside guidance when troubleshooting!