I have a 2GM20 which I installed myself in 1995. I have had overheating problems twice and both involved the exhaust elbow. I have a brass elbow which connects the water discharge line into the exhaust elbow once it was blocked with carbon the second time it was blocked by scale in the exhaust elbow. A long skinny screw driver cleared the debris both times. I now check the elbow each season. The engine normally runs below 180.I've been reading that lots of ppl has temperature reading for their cooling water out from engine. This interest me. I've Yanmar 2GM20F. Anyone has photos of the setup ?