I have a 2000 cruiser with 5.7 twin I/O mercs RWC. Last week I wanted to replace my thermostats because one was sticking and generally they both looked pretty worse for wear. When I pulled them, I noticed they were 160 degree 'stats. As far as I know, they are original equipment. So I took one to my favorite boat parts store and the guy said I should change from 160 degree to 140 degree 'stats. He said when you use 160 'stats, the engine will run to hot for RWC and the salt will eat at the "iron" quicker. So I changed to the 140 'stats. I'm all for a cooler running engine.
My questions are: Is the boat store parts guy right, or do those engines have 160 degree 'stats in them for a reason?
Second question is: I use strait 40 weight oil in both engines. Since I'm running a little cooler, should I change to a 25w40 oil? I use 40 weight because the mechanic that surveyed the boat when I bought it said 40 weight oil was better for those engines. I checked my manual and it calls for both 25w40 or strait 40 weight oil use.
I normally run in above the Chesapeake Bay Bridge water, which is brackish I'm told.
thanks
My questions are: Is the boat store parts guy right, or do those engines have 160 degree 'stats in them for a reason?
Second question is: I use strait 40 weight oil in both engines. Since I'm running a little cooler, should I change to a 25w40 oil? I use 40 weight because the mechanic that surveyed the boat when I bought it said 40 weight oil was better for those engines. I checked my manual and it calls for both 25w40 or strait 40 weight oil use.
I normally run in above the Chesapeake Bay Bridge water, which is brackish I'm told.
thanks