Thermostat question

[Bad Habit]

After a lot of time, trial and error (mostly error) i got the boat to run cool again. In the proccess I changed thermostst and a local marina recomended I use a 140 degree. After reading this and other forums it seems quite a few people use 160 degree thermostats in the same size boat. The boat is a 25 foot, fiberglass with a 350 5.7 (260 hp) mercruiser. The boat is used 95% of the time for trolling. any opinions or advice i appreciated. Thanks, Rick

[Capt Vince Pierleoni]

The only thing I can tell you is I put thousands and thousands of hours on several sets of 260hp 5.7 Chevys and I always had 140 thermostats in them and that was what was suggested in the manuals. It is true they may burn fuel a little better hotter, but too much heat KILLS.

[buckboardjr]

So what was the real fix to get it to run cool at idle?

[Bad Habit]

I pulled the lower unit and changed the impeller again and it seemed to be a lot better. I don't know if I did something wrong the first time, it was a combination of things or I just got really lucky. There wasn't any damage to it and it didn't look like it had take to much of a set but what ever it was hopefully is fixed. I have only run it hooked up to muffs but I hope to splash the boat and give it the real test soon. Rick