Trojan Boat Forum

Posted: **Mon Jun 09, 2008 1:13 pm**

Well Fellas,

I just finished up a ten day..(daylight til dark) (2000.00) rebuilding the top half of my 1974 Mercruiser 351 W / 302 Ford. Fun-Fun! Won't ever do that again...Anyway. My Thermostat gauge is not working properly. At first I had a automotive thermostat in there with an automotive sender... I happened on it in the book that I should never do that

and took it out before ever starting the engine. Still waiting on the sender to arrive tomorrow. Nonetheless, I don't see why the gauge is doing this.... When everything is off, including the key... it registers 220 and beyond (maxed out), when I start the engine it goes back to 180 and then slowly (within ten seconds) on over to maxed out again. Also, oil pressure gauge is maxed... Anybody?

Thanks,

John

Posted: **Sun Aug 10, 2008 4:41 pm**

John,

Some aftermarket gauges behave funny like that. They seem to "rest" wherever they feel like when they're not getting a signal. When you turn the key on, it drops down to a correct reading (about "0" when cold). If you're starting the engine dry or just circulating a small amount of water through, like with a pickup hose and bucket, it'll heat pretty fast. Up to 180 in 10 seconds is probably about right for bench running a dry engine. But it sounds like you had it in the water?

Pumping 50 degree lake water in there should keep it nice and cool, if it opens up the T-stat at all.

Whoever had my '61 292 Interceptor before me had no thermostats (it has mountings for 2) and I have no idea if the sender or gauge even work. It runs too cold, but I'd rather have that than the alternative hot chunk of iron in the middle of the boat. The water-cooled exhaust manifolds need a steady supply of cool water for sure. I'd hate to crack one of those babies.

I'd try it in the water with no thermostat first and see if the normal restriction of the pipes brings it up to an adequate temp like 180 or so. Just run it dockside or even on the trailer backed into the water, if you've got a launch where they won't breathe down your neck to get going.

Hope this helps.