Thermostat question????

[adm1476]

I have had evinrude/ johnsons most of my boating life. My new boat has a 200 hp Mercury on it. When I run it it seems to run way hotter than any johnson I have ever owned. Other than possibly getting a little bit better fuel economy what is the advantage of having thermostats. The engine is an 1989 so no fuel injection or computer. I am thinking about removing them so it will run cooler. Pretty sure none of my evinrudes have a thermostat. Even after running the motor wide open for 15 minutes on a run, I can rest my hand on the heads without even being close to burning them. My Mercury running on muffs for 10 min at idle or just off idle and I can barely touch the heads, they are that hot. And yes they are pumping water just fine. So let me know what you all think???

 

[wired247]

Re: Thermostat question????

Johnyrudes have thermostats too. The thermostats serve to maintain a minimum temperature. If you dont get the motor warmed up sufficiently you will wear the cylinder out faster. Leave them there or replace them with the lower opening temp 225 pro max thermostats

What is your water pressure at idle, cruise, and WOT? If you dont know you need to know. When did you last change the impeller. If its new to you or you dont remember its time to do it again.

 

[Faztbullet]

Re: Thermostat question????

A 200 Johnrude block holds about 4-1/2 gallons of water vs a Merc which holds about 2 gallons, that one reason they run a tad warmer. Also if to cold incomplete combustion and cold seizure is possible.

 

[Dukedog]

Re: Thermostat question????

Leave 'em in there. No heat, no horse power. Big difference in muffs and on tha lake............

 

[Mi duckdown]

Re: Thermostat question????

Muffs are great, and I use them all time, to make sure the motor will start. But you cannot diagnose/set anything until it's in the water.

 

[adm1476]

Re: Thermostat question????

ok good to know. So what should normal operating temp be with the stock thermostats in?

 

[wired247]

Re: Thermostat question????

On the muffs you arent going to get a good idea of the operating temp. The cooling system is only sort of working. On the water at should be in the 140-150 range but you can go up to 180 .

 

[adm1476]

Re: Thermostat question????

my boat has a temp gage but I also have a laser point and shoot temp gage. I will see and check it with both. I do not want to overheat it at all. The motor is an 89 but it only has less than 100 hours on it. It sat around for years, it was on a rescue boat.

 

[Mi duckdown]

Re: Thermostat question????

If it sat around for years. I would change the water pump impeller for piece of mind

 

[adm1476]

Re: Thermostat question????

I will be changing the water pump