3.0 mercruiser overheating - please help!

J

jon middleton

Cadet
Joined
Sep 13, 2009
Messages
17
I have a 2002 3.0 mercruiser that is showing an over heat on the gauge, it was running at 175F and recently is showing 190 -200 on the gauge . I have changed the thermostat, checked the impeller and changed the sender unit and it is still running hot.


What is the next thing to try? exhaust elbow ? when it is on the hose pipe there is plenty of water coming out of the exhaust at the transom does it still mean i have a blockage somewhere?

Is there any way of back flushing the cooling system with out taking off the exhaust elbow

Any help would be great!!

thanks
Jon
 
Bt Doctur

Bt Doctur

Supreme Mariner
Joined
Aug 29, 2004
Messages
19,111
Re: 3.0 mercruiser overheating - please help!

Best to replace the impeller using the full kit, You really cant tell a good impeller from a bad one by looking,
 
W

Wade95

Cadet
Joined
Oct 7, 2009
Messages
8
Re: 3.0 mercruiser overheating - please help!

Did you ever get it fixed? I ran mine all the way to 240*. My riser and manifold were toast.

Trying to figure out a way to flush the block to get rust particles out if there are any.
 
Bondo

Bondo

Moderator
Staff member
Joined
Apr 17, 2002
Messages
70,513
Re: 3.0 mercruiser overheating - please help!

I have changed the thermostat, checked the impeller and changed the sender unit and it is still running hot.
Click to expand...

Ayuh,... I Agree with BDr.... Impellers aren't Checked,... They're Changed...
New housings never hurt either....
 
F

FredGarvin

Seaman Apprentice
Joined
Jul 17, 2009
Messages
34
Re: 3.0 mercruiser overheating - please help!

I'd be curious about how this turns out too....I had my mercruiser 3.0 out on the water today and it was running hot. It's been running a shade over 170 for a while on the t-meter but today it was pushing up over 200 for a while and then was getting close on 220. It seemed to quickly jump when I'd throttle up and ease down when I let off the gas. I limped back to the dock at idle speed and now am unsure what to do. I'd be curious how the OP's situation turned out.
 
L

Lodgepole

Petty Officer 1st Class
Joined
Aug 24, 2003
Messages
272
Re: 3.0 mercruiser overheating - please help!

A dropped flapper valve blocking a part of the exhaust can also cause overheating. I had the problem on an OMC 3.0.
 
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