Gradual Overheat

[boatingfool]

1984 Volvo AQ125, closed cooling system:<br /><br />I run my engine and it warms up gradualy. Only problem is, is that it doesnt stop getting warmer.<br /><br />It will climb to 180 then slowly reach 200 then 10 minutes later 210 and it will slowly keep going up.<br /><br />This happens above 3000 rpm.<br /><br />When I bring her back to idle she cools down to 180 in about 5 minutes then once I start going again she starts to get hotter. Still very slow to climb but it will keep climbing if I dont bring her back to idle to cool down.<br /><br />Items replaced :Raw water impeller, thermostat.<br /><br />Removed heat exchanger and flushed it out. It looks pretty clean. A pebble here or there but thats about it.<br /><br />Any thoughts??

 

[boat doc]

Re: Gradual Overheat

what I typically find a slow overheat, especially as you increase idle is air entering the cooling sytem someplace pre-impeller. usually it is a water strainer, strainer gasket, loose hoses. It is probably not the right guess on a closed cooling system, but maybe something to consider

 

[boatingfool]

Re: Gradual Overheat

What about a bad radiator cap?? <br /><br />Where abouts in TX are you??<br /><br />I am in Wichita Falls.

 

[boat doc]

Re: Gradual Overheat

a good possability on closed cooling. Closed cooling on a boat does not run near the pressure an auto does. I used to deal a lot more with closed cooling than I do now, so I have forgot a lot. We now have a new engine out as of last year with a closed system, so now I am going to have to re-edjucate myself them......lol.<br /><br />I am in the big city of Mineola

 

[boatingfool]

Re: Gradual Overheat

Thanks for the help Doc.

 

[Northern Eclipse]

Re: Gradual Overheat

Is the exhaust manifold and riser FWC or RWC?? if one or both are Raw water cooled, could be a possible problem, also check your cooling hoses and make sure one of them is not kinked or collasped, I,m not a volvo expert but If I remember correctly they had a belt driven seawater pump, if so look for a worn or slipping belt. One other thought is on the outside of the boat at the outdrive is there a water pickup that might be leaking between outdrive and transom assembly? I'v seen this with mercs with rotted cooling hoses, not sure if volvo is similar but its just a thought.

 

[akriverrat]

Re: Gradual Overheat

should be an oil cooler on starboard side of engine. a restriction there could be causing the problem.

 

[boatingfool]

Re: Gradual Overheat

No oilcooler.<br /><br />Thanks again for the help guys.<br /><br />Anything helps.

 

[boat doc]

Re: Gradual Overheat

typically clutch shift type outdrives have a engine mounted raw water pump<br /><br />shift dog (lower foot) have an impeller mounted in o/drive.<br /><br />just something for future refrence

 

[dick]

Re: Gradual Overheat

The way water is sucked up to the pump on volvo engines can be a problem. There is a hose connection below the u-joint bellows that rots out.Also if there is to much play around the h-fork area it will suck air when the boats on plane. The best way to check is get some clear hose and install it between the inside of the shield and the pump.Take out he boat and while someone is driving look for air bubbles in the hose.One more thing those engines do run hot . 195-205 is normal.If you have the old style volvo gauge (which I assume you don't because you know the actual temp )the needle is just below the red line.This freaks out alot of people.