Mercruiser 470 Overheating

[falcon50]

I'm new to I/O so I apologize for posting a topic that has already been "beat to death". But I don't know where to start. The boat is a 1981 Imperial with a "470" 170 hp, 224 ci, 4 cyl. Mercruiser. When cruising at 2800 rpm temp is at 165 but as soon as I cruise faster the temp starts to rise. I understand a water pump has already been replaced in the stern drive. The only thing I noticed was that the radiator cap on the closed side was old and not sealing. I'd appreciate any help.<br />Thanks,<br />Bill

 

[skelly]

Re: Mercruiser 470 Overheating

Wat up Falcon50! I too have a 470 merc 1979 .sounds like the Problem i had 3 years ago it turned out to be a rusty exhuast elbow restricting cooling water flow. if it has not been replaced in the last 5-6 years or so then it is time to replace it. and if you are running in salt water!! Make it 4-5 years. This is an easy job, just 4 bolts & gasket.Hope this helps you,.

 

[jfc092]

Re: Mercruiser 470 Overheating

Ditto - "Exhaust Elbow"

 

[falcon50]

Re: Mercruiser 470 Overheating

Thanks for the tip. Any suggestion of a good WEB site to find the exhaust elbow. Also, everyone talks about serial numbers, where can I find the serial number.