Mercruiser 470 temperature normal operating temp

[ohm529]

I have an '87 Sea Ray with a 470 in it and I watch the temp like a hawk. Took it for a cruise last night and after 20 minutes running around 3800 RPM's the temp was at creeping up to around 175 degF. This is the middle of the gage, but what is the normal operating temp for this engine and at what temp should I get worried and slow it down?

 

[Brentathon]

Re: Mercruiser 470 temperature normal operating temp

Normal operating temp is predominantly set by the temp rating of your thermostat. If your t-stat is 140F, I would say temps in the 175F signify somethings up with your cooling system.

 

[stonyloam]

Re: Mercruiser 470 temperature normal operating temp

From the "book": "Normal operating temperature taken at the temperature sender with a direct reading gauge is 165? F to 200? F" According to the manual, thermostat should open at 155-162, and be fully open at 183. So you are OK.

 

[ohm529]

Re: Mercruiser 470 temperature normal operating temp

Cool, thanks

 

[guyaverage]

Re: Mercruiser 470 temperature normal operating temp

There are plenty of 470 owners that would love to only see 175 after cruising at 3800 for 20 minutes.

As long as you dont starting creaping up around 195-200, I would look for consistent temps rather than the raw number.

Mine too typically runs in the 170-175 range at high rpms, two summers ago it started nudge a bit over 180 after a 25 minute ride close to 4000 rpm in cooler waters than I normally boat in, so I knew something was off. Got home, dropped the lower to check the pump, found 2 of the impeller vanes were pointed in the opposite direction of the others. Not sure how that happened, I guess it had to have been during the install. But if owning a 470 hadnt led me to obsessive-compulsve staring at the temp gauge, I probably wouldnt have noticed the extra 5-7 degrees.

 

[stonyloam]

Re: Mercruiser 470 temperature normal operating temp

As long as you dont starting creaping up around 195-200, I would look for consistent temps rather than the raw number.

Agree! That is the key, the temp should be stable, if creeping up start looking for the cause. For now, have fun

 

[Brentathon]

Re: Mercruiser 470 temperature normal operating temp

I thought a T-stat should start to open at the temp stamped on it (rated temp) and be fully open 25F above that temp, no?
So, for my 5.7L Alpha with a 140F T-stat, what does "the book" call out for normal operating temps?
I would think that a fully-open T-stat should cool-down the engine until it starts to close again, and so on , and so on...correct? So where is the 200F coming from? That seems pretty high.

 

[stonyloam]

Re: Mercruiser 470 temperature normal operating temp

I thought a T-stat should start to open at the temp stamped on it (rated temp) and be fully open 25F above that temp, no?
So, for my 5.7L Alpha with a 140F T-stat, what does "the book" call out for normal operating temps?
I would think that a fully-open T-stat should cool-down the engine until it starts to close again, and so on , and so on...correct? So where is the 200F coming from? That seems pretty high.

Different system. The 470 has a closed cooling system, with a pressure cap on the reservoir. Antifreeze is cooled (by a seawater cooled heat exchanger) and recirculated. This is different from the open system where water comes in one end and out the other. I know nothing abut your system, just trying to keep mine from overheating, sorry.