Running to hot??

[magregor22]

I have a 470 Merc that I beleive is running to hot. The heat guage says it's not getting any hotter than 180 but you can't touch the motor anywhere including the side of the block, valve cover, intake manifold ect. Even parts like the oil filter,carb and alternator feel too hot. Also when I shut it off the coolant will boil over sometimes. I run some searches on this forum before posting and here is a list of things I've tried before I posted this.<br /><br />1) Changed the Impeller on the outdrive<br />2) Took the heat exchanger apart and checked for blockage<br />3)Took the exhaust elbow off and checked for blockage or corosion.<br />4) took the thermostat housing off and blew out all the passages in the exhaust manifold and therm. housing.<br />5)took the cover off the freshwater pump and inspected the impeller(looked great)<br />6) Blew out all hoses and passages with air<br /><br />I am now out of ideas, when I run the boat with the garden hose and pull the line off the heat exchanger seawater intake line the water flows solid but only jets out about an inch before falling off. If I rev the motor it shoots out about six inches before falling off.<br />any help would be greatly appreciated.

 

[Peter J Fraser]

Re: Running to hot??

All these points you have checked will be too hot to touch when upto operating temps.<br />Remember that anything over 100F will start to modify your finger prints darn fast.<br />The alternator will heat up rapidly when it is working. That is normal and why there is a cooling fan on the alt.<br />The oil in your oil pan and filter could easily be over 150F. OUCH - Burn your fingers. <br />I have seen Pan oil temps on a race engine pushing 200F with ease.<br />If you can beg borrow or steal from a buddy, an Infrared Temperature Gun you can run all over the engine and check for HOT SPOTS in your cooling and lube systems.<br /> <br />Regards<br />Peter

 

[Haut Medoc]

Re: Running to hot??

I suspect the heat exchanger. The problem is that when you take off the end caps everything looks good. This is the sea water side. What you cant't see is the fresh water side where the heat exchanging actually takes place. My advice is: beg, borrow or steal a new exchanger if you can to test or take the old one to the radiator shop and have it boiled/rodded out. Go new if you can. I'd bet money that this is your problem...............J

 

[magregor22]

Re: Running to hot??

Thanks for the advice, you guys are great. I haven't been able to get my hands on another heat exchanger or temp gun but you got me thinking that last year I had a hole in my heat exchanger and had it repaired, but seawater(salt) got into the freshwater side and maybe that was causing havok on the aluminum block. i did flush the system with water last year after I had it repaired but yesterday I run a couple of bottles of rad flush through and took both the cooling systems apart and blew them out. Started the boat and she is running much better. hopefully that's it for that problem and maybe I can get an hour or two of boating in before my next 10 hours of repair. cheers gary

 

[vipzach]

Re: Running to hot??

You didn't say anything about the thermostat itself, did you change it to?

 

[magregor22]

Re: Running to hot??

I took the thermostat out and tested it in a pot of water, and also tried running without it in but it didn't make a difference.

 

[Northern Eclipse]

Re: Running to hot??

If you need to get a new exchanger go to a 4 inch alot of older 470 suffered high temp problem due to the 3 inch heat exchanger, Merc changed to the 4 inch when they started marketing the 470 has the 3.7L