When I say sides I mean the side of the thermastat body and not the top rim. Do you have to run a bypass. When I purchased my boat it did not have bypass set up. Am I damaging anything. Had no problems thus far.
Thanks

If you run a thermostat with a crossover, you must run a bypass. Not doing so results in not enough water going into the exhaust to cool it properly and too high water pressure when the therm. is closed. A couple of 1/8 holes will not flow enough water to make up for a bypass. No Cigarrete, I'm assuming that you were running without a thermostat before?Merc always used 140 degree thermostats in their carb engines. I'd feel safer running poker runs at 4000 rpms plus for long distance with a cool running engine.

I know this sounds dumb but....I am assuming that my x-over has a bypass because it has a short 1" hose coming out of the x-over into the thermastat housing with 2 more hoses coming out of thermastat housing and going to headers. Is this considered a bypass? It is a eddie marine thermastat housing that is tall, has a spring in it and a plastic peice that sits on top of this spring inside of housing. Boat came with this set up. Is this a by-pass set up? Have run this 1 season with 143 stats and 2 holes drilled in the outside body of stat. Do not have water press gauge or oil temp gauges. Engines run at 150-175*. When you are running say 4,000 rpm in summer you can watch temp gauge and see the temp start to drop when reaching 175 and levels out to 150 and then back up to 175*. I am supposing the thermastat opening and closing? Is this set up working as it should or am I headed for trouble.

Team Tickfaw,your setup sounds fine to me.If you are ever too hot drill another 1/8 hole in the thermostat.You do not have to run a bypass when you use a thermostat as long as you have at least 2 3/16 holes in the thermostat rim.I find it actually easier to "dial in" the prefered temp without a bypass because that way you know all the flow is going through the engine.Just remember the thermostat holes.More holes for cooler,less for warmer.

Team Tickfaw, sounds like you have a bypass.

Thanks guys.

If you dont run the bypass you really need to monitor water pressure ... over 30lbs can be trouble .... I bet some post 30lbs is too hi ....

Just Curious ... what oil temps you running ? and water temps?

I actually run two senders one in the pan and one in the oil relocation housing...I have a toggle switch on the dash to swich from each....I run real low oil temps thats why i added the oil thermo this winter, my cooler is a monster.....Maybe 4 in by 22 in long, a big gil offshore cooler...