Merc 470 operating temp

[rwendt]

The last couple of times out on my 1980 Hurricane deckboat with a Mercruiser 470 it seems to be running hotter than it was. I am in Northwest Ohio on the Maumee River.

What is the typical operating temp range?

It used to run just a little above 160F to the 80 C makrs on the gauge. Now it is 80 C to 90 C and a tick above. Should I be concerned?

I am thinking maybe the lower unit water pump impeller is worn and needs to be replaced, I hope to wait until the end of the season

Thanks

Ron

 

[crazyinkc]

Re: Merc 470 operating temp

Have you checked you heat exchanger for blockage/bulidup? When was the last time the impeller was done? Are you loading the motor more (ie, more people, gear, higher pitch prop)? How is the coolant level in the closed system?

 

[rwendt]

Re: Merc 470 operating temp

Crazy

I have owned the boat for 4 years now and I have not replaced the pump yet. It was pretty well maintained before I bought it. Is there a time frame when it should be changed?

I have not checked the heat exchanger either, nor changed the antifreeze although I sucked out what I could out of the overflow tank and refilled that. I really am not sure how to take apart the exchanger or to drain the whole system or flush it. I was intending to look into this when I pull it out for the season. I do drain the water out of the system every year

I run it like always, 2000-2800 RPM with just a couple of people in it. We are lucky to go out once a week for a couple of hour cruise and float.

I just changed to a new overflow tank and the level is just fine. The antifreeze looks like new.

I do not know anyone else with this engine so I really do not know what to expect. The water temp in the river is up near 80F so that certainly could have an effect on the engine temp

Ron

 

[Haut Medoc]

Re: Merc 470 operating temp

I would say that you need to replace the raw water impeller....
If it loses some vanes, you will be retrieving them....
So that is a roll the dice option, if it will last to the end of the season....
As for the heat exchanger, pull off the endcaps & look for encrustation or corrosion in the tubes.....
My guess is the impeller......​

 

[skelly]

Re: Merc 470 operating temp

I have a 1979 470 that where over time the temp began to rise, it turn out to be the exhuast elbow was stoped up with rust ,this is were the exhuast and over board water mix on the way out (Vary Corrosive Here)I was told to replace about every 5 years , This is a simple fix , Just 4 bolts & gasket & hose clamp, about $140.00 Look at it like this , If water can't get out then water can't get In and makes the other cooling parts work harder......Hope this helps you...........Pull it off and check , Just use new gasket to replace if good.