Re: 95 evenrude 115
Yeah, you can't always trust the telltale as they are seemingly "pressurized" to a point and think that makes water deceptive. I would drop the lower unit and have a look see at the impellar. If it's in good shape (still plyable, not cracked or having broken nibs), then I'd leave it and we'll go from there. Do you have a service manual? The thermostats would be the next culprit to start looking at, but they're a bear to deal with. Hopefully you'll drop that lower unit and find a corroded old impellar and that will be all she needs.
Since the motor is new to you, it never, EVER hurts to buy a basic compresion tester (Harbor Freight for like $10.00) and do a compression test to make sure everything is as it should be. If you've got a Harbor Freight, then it also wouldn't hurt to pick up a basic spark tester while you're there. A lot of prevention while she's on the trailer can make for a lot more happy days on the water. As I'm sitting here browsing iboats, I've seen one neighbor pulled in by SeaTow and another yelling up to me that he had to "crawl home on one motor" (two engine jet boat). Knowing both of these fellows (good guys, btw), neither one of them even looked under the hood to see if they still had sparkplugs, let alone did any checking, lol.