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'Whirring' Noise - 1977 Mercury 75/7.5 hp, 2 cyl, 2-stroke

tronicsmasta

New member
Hello Everyone.

I have a 1977 Mercury 75/7.5 hp, 2 cyl, 2-stroke. We call it "the engine that think it can!" She is a beautiful engine thats on our 13 ft Gregor...

She works great. I cleaned the carb and tuned her up. Her idle isn't too rough.

After about 1 to 2 hrs of continuous running time, she starts whirring... not in idle but when at 1000 rpms or higher in gear or not in gear. Its puzzling to me because I can't really start to take it apart when we are in the middle of the lake or behind the break wall.

I do have a subscription for this engine to Seloc Online if needed.

Any ideas on where to start trying to narrow it down?

Thanks in advance!

Q
 
Without knowing the history of the motor ( was it ever sunk and not recovered properly etc )---It is hard to say.--------------I would start by looking at the lower unit oil.---Any water or metal bits present ??
 
Without knowing the history of the motor ( was it ever sunk and not recovered properly etc )---It is hard to say.--------------I would start by looking at the lower unit oil.---Any water or metal bits present ??

I took a look at the lower half... I was getting ready to pull it to see if there was water in the oil and i see the lower half leaking oil thats milky between the prop and the lower half body... I think you might be right.... Ill pull it and get back to you.
 
Without knowing the history of the motor ( was it ever sunk and not recovered properly etc )---It is hard to say.--------------I would start by looking at the lower unit oil.---Any water or metal bits present ??

ok... So i drained the oil. There wasn't any water in it... it wasn't super dark brown and it wasn't like a light coffee... I did notice a leak of milky oil from behind the prop. I think that seal needs to be replaced but I can't seem to figure out how to remove that spanner collar and get to that seal. I am going to replace the oil and if you guys have any idea how to replace that seal I will replace that too :)

Thanks again!
 
???? Noises are the hardest to diagnose.Look under the hood and under the flywheel for metal shavings.
Any color other than black or the original usually means water.
There are several threads for a homemade pressure tester.Here or on other sites.
i boats. com , Force Forum use the search function both sites.
 
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