1975 50hp 50esl75b Cooling System

Hello, brand new to forum and brand new to boating. Bought a 1975 50esl75b which had sat awhile, installed carb kits, new fuel pump, new fuel lines, starts and idles great! I also bought a new water pump to install yet. Have only ran it for a minute at a time with the muffs on. Looks as this motor has no tell tale? there is two slots on back of motor just under the engine which I think should let water out, just not sure if water should come out of these slots right away or after the thermostat turns on? If the water is supposed to come out of these slots after startup, I'm guessing it is not possibly if the old water pump cannot push enough pressure? Planning on installing new t stat also as should be quick cheap insurance.

i'm very interested in adding a tell tale unless a new pump shows water coming out of the two slots on the back. If some could verify this I would greatly appreciate it. Would adding the tell tale prevent the thermostat from operating as much and not running at optimum temperature? Any pictures of installation on motor like this?

finally, after the short amount i idled it there was a tiny amount of water sitting in the engine mount bracket beneath the electrical. Guessing either the t stat or gasket leaking? Any thoughts? Something I should be worried about or needed to start replacing gaskets back there?

thanks!

Red circle shows the slots on the back of the motor I was talking about above.

Thanks

Keaton

Water will spit out those 2 holes at idle.-----------Motor has lived for 40 years so no telltale is needed.----------Replace the impeller on a regular basis is the thing to do.----------Have seen many motors with telltales suffering from overheat so to me they are useless.---------Test the overheat warning horn that is in the control box too.

Thanks racerone! Any comment on the leaking around the head? Just new gaskets?

I've got pretty much the same motor (mines a 72) but it won't run on muffs. For whatever reason, it won't pick up the water even with a new pump. It works fine in the lake or running in a barrel, just not on muffs.