'76 Merc 888 started running too warm. <br /><br />Last week, I dropped the LU and changed the entire water pump this time, new base, impeller, and housing. Also pulled the tstat and checked it, tested out ok. The tstat is a 140deg.<br /><br />Took the boat out Saturday. It idles perfectly at 140. At 3200-3500rpm it warms to 160. During a short WOT burst of about 30 seconds, the temp went to 165. Dropped back to 3000 fro a few se\conds then idled in gear for 10+ minutes. It took most of that time for the temp to go back down.<br /><br />Any ideas? The engine/manifolds have <100hrs freshwater use. The risers aren't much older, but spent one season in salt. When I put it together a couple years ago, the risers looked perfect. Someone has suggeted a stiff or sticking exh. shutter. These were replaced during rebuild. I've pulled hoses and seem to get ok water flow. I'm stumped.
I dont even have an hour meter