Good morning and thanks in advance for any help you might be able to offer. I have a Mercruiser 5.0 MPI in a 2009 Bayliner cruiser. It is equipped with the Bravo 3 dual prop out drive and I have owned this boat since new. I use this boat in the intra-coastal waterway in Florida. The boat is dry docked and well kept. A few months ago it over heated. The mechanic started at the sea water pump which seemed fine. He then went to the thermostat and housing which were both replaced. It was still over heating so we replaced all exhaust manifold system parts. I used the boat once and everything seemed fine. It ran just over 175 on the temp gauge which is normal. The next time I used it the sea water pump locked up and I believe broke the shaft as the pulley moved forward an inch or so and thew the belt. I purchased an aftermarket pump, making sure it wasn't the cheapest unit out there, and had him install it. We used it for the first time yesterday and I brought it home early with temp concerns. I ran it up to about 4000 rpm and it warmed up to the 175 temp quickly. It then slowly climbed up to the temp shown in the attached picture. I'm thinking that's somewhere around 205-210. The alarm never sounded at this temp. I slowed down to run it in idle zone speeds and it comes right back to 175. My mechanic said that the alarm will sound at a true 205. My questions are... is 205 the correct alarm trigger? Also with all these new systems would you have any advice as to what may be causing this over heating?
