Velocity280
New member
Hope someone here has experience with this, and can help me out. I have a new engine in my boat. Gen 6 454, carbureted. There's not much mercruise left on it. New gm block, Brodix aluminum heads, Holley carb, aftermarket marine oil pan, Merlin aluminum intake , and Dana products water cooled exhaust manifolds... I've been having an issue with my temp gauge fluctuating. I've tried numerous thermostats. With bypass holes drilled with, and without. Currently I have a 140 thermostat in, with no bypass holes. The boat will come up to temp, around 150, then when I run it at anything higher than 3000rpm, it will slowly climb to 180, then from then on, it will climb rapidly to 240-250 (max the gauge out), first time I saw this I shut down right away, opened the hatch and checked everything out. All looked good. I got an infrared temp gun, and ran the boat to show these temps on the gauge again, and the block appeared to be around 165-175 , while the oil lines are around 200-210. I'm pretty convinced the engine isn't actually seeing these temps, but where should I look to fix the issue why the Gauge is registering these numbers?