mercruiser gm 350 overheating

[sarantis]

The 350 block is new,the water cooling system (fresh water) is that of gm305 1978 (long manifolds with the elbows at the back,Tstat housing with the 8 hoses).Even at idle the engine overheats.The incoming water seems enough good.No air bubles get to the system.Both sides of v-block are the same hot.New temperature sender,thermostat housing,thermostat.Relatively new and checked manifolds and elbows.All hoses checked.I have the impression that the water resulting to the elbows is not enough.So the only thing i have not replaced is the (about 5 year old)water circulator and that because it looks in good shape,i 've inspected internally and looks good and it's saft hasn't side to side play.Is there any test available for the circulator?Do they are faulty only when they leak?

 

[cooter2506]

Re: mercruiser gm 350 overheating

How about the impeller in the outdrive?

 

[sarantis]

Re: mercruiser gm 350 overheating

New impeller,impeller housing,i said the water flow exiting the ps cooler is very good

 

[cooter2506]

Re: mercruiser gm 350 overheating

Are they the original manifolds. If so they are way over due to be changed. Sorry about the impeller thing but seems good enough and having new impeller meens two different things to me. You didnt put the tstat in upside down did ya? Spring should be down.

 

[sarantis]

Re: mercruiser gm 350 overheating

Manifolds are two years old and cleaned and i put the Tstat with the "nose" up.But even without the thermostat the needle passes the center at idle.

 

[J. Mark]

Re: mercruiser gm 350 overheating

did you lose an impeller previously and if so did you account for all of the pieces?

How are you measuring temperature? A inaccurate gauge or bad sending unit could have you chasing your tail for nothing.

An infrared thermometer is a great tool for finding out part temperatures an even helping to locate where the problem lies.

If this is a just rebuilt engine make sure you have the correct circulating pump (on a car I'd just call it a water pump) and not one that rotates the wrong way. and yes water pumps can fail without leaking, but it is not the norm.

 

[J. Mark]

Re: mercruiser gm 350 overheating

Home depot sells an infared thermometer for $50.00

http://www.geeks.com/details.asp?In...edium=ShoppingSites&utm_campaign=IR-THERMOMTR

Looks just like this one.

 

[sarantis]

Re: mercruiser gm 350 overheating

In the past there had been an overheating but since then the block and everything else was replaced.Temp sending unit also replaced.I don't think that the gauge sudenly lies but i 'll check again with an IR thermometer.Is there any possibility that one swaps from a 305 to 350 and doesn't use the same water pump?