I recently took the thermostat out of my truck to replace it. I couldn't find the correct one for it anywhere. I finally put one in out of a Jeep Grand Cherokee but no one needs to know that but I googled the serial number and they are telling me it's a marine engine. The number is 6b5.9-180. I talked to a diesel shop and they don't think it is one. Can anyone tell me for sure if it is a marine engine?

 

"6b5.9-180" is the series number, not the serial number. It's for 6 cylinder, B-series, 5.9L, 180 hp. Sounds like a standard Dodge late 90's configuration, as the "industrial" ones were generally 190 hp configurations (and a completely different pump cam, from what I've learned) and the "marine" engines were rated much higher and generally had special stuff for hull cooling and whatnot if it was a TRUE marine spec motor.

Does the engine have a information tag rivited to the timing gear housing? That will generally tell you everything you need to know...

As for the thermostat, any B-series one should work....how could you not find a Dodge 12 valve Cummins thermostat? Most parts stores should have it...as well as Dodge and Case/IH dealers...

They make a few preset degree thermostats. According to Pure Diesel Power:

Cummins 180* Thermostat: P/N 3928499
Cummins 190* Thermostat: P/N 3946849

Then you'll need the sealing rings too: P/N's 3925466, 3927305.

 

I pulled thermostat from mine and went to napa and auto zone. I got several different ones and none of them even fit in the housing... Apparently something isn't right.

 

The dumb ***** probably gave you one for a 5.9 Gasser