1971 225 getting hot! At the end of my rope!!

[Skippy the skipper]

I've got an old head question for anyone on a 71 225 OMC electric shift stern drive I have been working on forever. It gets hot is the basics of it. Runs 3/4 on guage at idle. Will slowly climb on a load and drop back to 3/4 when you reduce rpms. I have quite a list of what I have done to it so here it goes....

ck oil, has no water in it

Changed the impeller

set timing

replaced thermostat and housing

replaced temp sensor

Replaced water pump on engine

swapped temp indicating system from other engine (still runs hot on other indicating system)

put radiator cleaner in block on warm engine to flush

removed/reinstalled intake and heads....had heads magnafluxed and valves ck by machine shop

performed flow tests on each portion of cooling system. (found values in old omc book, so much per 20 sec ect...) Passed....small bubbles at first then clear flow on clear tubing

replaced 1 exhaust manifold that was cracked, inspected other and found nothing but cleaned it out anyway.



I'm at a loss and fairly frustrated any help would be greatly appreciated. I did ck engine with dig temp gun and it is running hotter than the other side but other is a newer engine

Thanks in advance...Skippy!!!

 

[bruceb58]

Re: 1971 225 getting hot! At the end of my rope!!

I would double check what you think your temp is by checking with an handheld IR gun.

 

[Howard Sterndrive]

Re: 1971 225 getting hot! At the end of my rope!!

despite the lack of bubbles, grease the swivel bearing at the lower unit- didn't see it on your list

was the clear hose test done in the lake? on plane?

 

[Skippy the skipper]

Re: 1971 225 getting hot! At the end of my rope!!

I did ck with the heat gun but did not write down the temp, will do this weekend

 

[Skippy the skipper]

Re: 1971 225 getting hot! At the end of my rope!!

the clear hose test was done only at idle, not under way.

 

[Howard Sterndrive]

Re: 1971 225 getting hot! At the end of my rope!!

the clear hose test was done only at idle, not under way.

it needs to be done on plane to be valid. Under load, on plane, you would most likely discover more exhaust gases than water being drawn in due to a lack of grease in the swivel bearing - service manual calls for grease twice per season ot keep exhaust out of the water pump intake path.