1978 mercruiser 470 running hot

[olazabel]

Engine temp has been creeping up around 200 degrees this spring.

I'm planning on flushing the cooling system, changing the thermostat, and changing the impeller, but I'm not sure which parts I need (or exactly how to do it)

The engine serial # is 4773471

and the outdrive serial number is 4680971 (1.84R)

If anyone could point me to the correct part #'s and manuals with instructions I'd appreciate it.

Thanks in advance.

 

[stonyloam]

Impeller NOW!!!

 

[olazabel]

I think the thermostat I need is sierra part # 18-3552 (160 degree)

And the water pump kit is 18-3317 (but there is a note about boats retrofitted with alpha drives requiring different parts, don't think I have that, but not sure)

anybody help me out on this?

 

[stonyloam]

Waterpump kit here: https://www.mercruiserparts.com/Sho...bnbr=70&bdesc=GEAR+HOUSING+ASSEMBLY,+COMPLETE. I would do the whole thing, housing and impeller, OEM parts, then new impeller every couple of years. 46-96148A8

 

[olazabel]

thanks stony- I got the whole kit at NAPA. I took the old impeller out,and it was toast. looked like it hadn't been changed in at least ten years. Anything else I should do while I'm in there?

and... for future reference what is the outdrive on my 470 called?

 

[olazabel]

I changed the impeller, gaskets. housing, etc. put it all back together..................... and now the boat won't shift.... when i try to spin the prop by hand it feels like its in reverse

so my new question is what did I screw up, and can I fix it by tomorrow so I can take my kids out on the boat?????


there was a small splined thing that fit into the end of the shift cable inside the lower housing I think. maybe I screwed that up somehow?

 

[stonyloam]

If there are pieces of the impeller missing, look for them under the front cover of the heat exchanger. A bad impeller is the most common cause of overheating. A dirty exchanger can lose efficiency, but far less common. The other place where you can run into a problem is from crud buildup in the exhaust elbow that restricts raw water flow through the exchanger, again, not usually the rot problem. I think you have a what they call a165, here is a link to the parts diagram for your sn https://www.mercruiserparts.com/selectSerailRange.asp?doc_nbr=165++++++++1970-1977. While you are back there lube the hinge pins, gimbal ring swivel pins and prop shaft with quicksilver 2-4-C, and the gimbal bearing with Quicksilver Extreme grease. Do you have any play if you try to move the outdrive back and forth?