Mine runs at 185ish, and I was told the gueage may be a little off. They said if I was unsure to take an actual reading from the engine myself.

 

I've got a 5.0 MPI and my thermostat kicks in at 160 degrees. When I am haulin' butt it stays between 162 to 165. I wonder how accurate the temperature sensors are though ?

 

Once warmed up mine stays just below 170.

With your description I would be concerned about a impeller issue.

 

Once warmed up mine stays just below 170.

With your description I would be concerned about a impeller issue.

Thats what I was worried about but the outdrive is brand spanking new... Not a rebuild according to the dealer who replaced it. I would hope that means that the impeller is OK, but I guess anything is possible.

Anyway, I just called the dealer and they will be looking at it soon.

 

Very unusual for temp swings that far apart unless something is wrong with the impellor or maybe the water pump. Might be that a hose was left off? Any water in the bilge? Did you get any high temp alarms?

:smt017

 

No water in the bildge and no alarms.

I was looking over the Stem to Stern website and the parts breakdown of the thermostat assemby. The thermostat itself says 160 degrees....!?! If the thermostat is supposed to start working at 160 something is definately wrong. I know there is water getting to the engine because the fronts (inlets) of exhaust manifolds jackets were cool. I don't have a good handle on the water flow sequence through the motor but if I'm getting water that far I'm betting on a bad thermostat. I'll have to wait to see what the dealer says.

 

I am running both around 165 very consistantly.

 

two things come to mind, either a faulty guage or air in your cooling system. I had a guage oscillate because of a bad ground as well. It should run right at 170+-.

briman

 

Mine's at 170 when warmed up.

 

Mine runs at 170 normal.

 

Your temperature swings precisely match the exact same symptoms in my auto when my thermostat starts going bad. I'd throw a new thermostat in before spending all that money paying labor hours to someone else. It won't cost you much of anything.... you can install it yourself easily, take the boat out for a quick spin, and if it still has the same symptoms you're only out a new tstat (which it never hurts to have anyway) but it may fix it and in that case you will have saved a whole lotta money. There's nothing at all to lose by trying.

 

170 degrees on the button.

I was thinking the same thing as Gerald: Bad t-stat.

 

after reading this thread i paid more attention to the the temp tonight.

never did it get over 161 even when i was cruising at WOT. most of the time it was in the mid 150's

2006 220 select, 350 mag, about 35 hours on the boat

 

There are two common tstats - 140 degree and 160 degree. If you're running normal you should see temps about 10 degrees above the tstat. You might have a 140 degree tstat in yours.

 

My 3.0l has a 142deg. thermostat in it. I wonder why it is so low? The hotter the engine is, the more efficient it is (why most autos today run 195-205)...to a point obviously. I wonder if I can go to a 160 aftermarket thermostat (if one is available), safely? I can't think of any reason why not....or why they picked 142 in the first place.

 

I spoke to my dealer yesterday and was told that my boat (4.3 MPI)should run at 170-175. They said it is possible that the raw water intake might have picked up something which would increase temp. Also said that early in the season the t-stat might be sticking a little. Anything over 200 is BAD, BAD, BAD! He also said that on this engine running the engine hard before it is warmed up (under 140 degrees) does as much damage as running it at too high a temp. So make sure your motor is warm before dropping the hammer.

They suggested giving it another try and if I was still concerned they would recommend taking it in to have is looked at. I might take it out tomorrow to see if the results are any different than my first try.

 

5.0 here that runs a tick over 170 religiously once warmed up.

 

He also said that on this engine running the engine hard before it is warmed up (under 140 degrees) does as much damage as running it at too high a temp. So make sure your motor is warm before dropping the hammer.

Thats good advise for any motor. It also highlights the importance of using the right oil. The oil needs to get some temp to it before running hard. Some engines may be less affected, but as a rule of thumb, unlike cars that can heat up the coolant quickly and maintain the temp, boat motors are being cooled by water thats constant and cool and take longer to bring oil temp up.

 

sighhhh.... guess it's good there has been too much debris to float lately. Im still waiting to get my t-stat checked out for cold running engine. ( and glad I never really 'opened' her up before)