I have a 98 Sea Ray with Twin 2003 5.0 MPIs. One seems to run hot, but only the upper part. Smart View says both engines run fine around 170. However the upper risers and thermostat housing when shot with an infared gun say otherwise. After the engine is running just a minute, the thermostat housing on one, reads 90 or so. The other 150. The upper risers on the good one reads 150 on one, 230 on the other. Lower chamber down by the water pump reads normal on both. Impeller has been changed, thermostat has been changed. Water pump works well. It's really confusing and I am pretty good with this stuff so I hate to pay mechanic to tear it apart. I recently brought it home and at cruising everything runs much hotter. By the time I got it home, 40 min trip the alarm on the port engine was going off, though smart view couldn't tell me why. When I shut off the port engine, the alarm went off immediately. Both engine ran fine on the trip and did well, but its quite obvious its getting hot somewhere. I was sure it's somewhere around the thermostat housing as thats the first thing I notice hot, but it doesnt seem to be. I did notice a sort of ground wire on the left of that housing that is badly corroded and falls off, but I dont think its related. I am guessing that goes to the sending unit. Any ideas what could be going on?
