I have the 1998 Mercruiser 4.3 Alpha carbed motor. The MC321 kit installed, dry joint exhausts installed and has ran fine for the last 10 years. After changing the (weeping from the shaft) GM water pump recently, I noticed the port side exhaust manifold was 50 degrees hotter than the Stbd exhaust manifold, 210 vs 160 but the helm temperature gauge still showed the normal 170 after warm up. Compression check was good and consistent. I next removed the risers and confirmed all was clean and no water blockage issues. After reassembly there is still the 50 degree difference despite painstakingly burping the air out of the system. The 140 and 160 thermostats I used have function tested perfectly on the stove, opening widely and timely at their respective temperatures. I next removed the thermostat and ran it on the hose again. Both exhaust manifolds temperatures were dead even through 15 minutes and various rpm so we know the system has no blockages now for sure. My question is...does the SJE MC321 kit thermostat housing have a water routing difference that shows only between port and starboard when a thermostat is installed? Is a diverter needed like the OEM system to even out the flow? Or?
Once again, thank you for your insights.
Once again, thank you for your insights.