350 Mag 5.7 Ltr cooling problem..

[Direct Deposit]

Hey guys, thanks in advance for all of your help... I own a four winns 211 liberator with a mercruiser 350 magnum 5.7 ltr Alpha one.I'm having major issues with cooling my engine. The thermostat goes up gradually withing 10 minutes to 240 F. I have changed the impeller in the lower unit I have placed a new thermostat I cleaned the exhaust bellowsand I checked my water pump, my impeller on my water pump is metal and it looks ok. Today I turned on my enging and it started cold and after 10 minutes all of the tubes connecting to the engine became super hot. Can you guys advise me on what might be wrong.

Again thanks for your help.

 

[Bondo]

Re: 350 Mag 5.7 Ltr cooling problem..

I checked my water pump, my impeller on my water pump is metal and it looks ok.

Ayuh,.... I see 2 Issues here,...

#1,.. This is the Mercruy Outboard forum,... You have a Mercruiser I/O,... Wrong Forum...

#2,.. You need to replace the Raw Waterpump Impeller,... It's located in the Outdrive...
The circulating waterpump is what you Checked,+ they Rarely go Bad...

 

[QC]

Re: 350 Mag 5.7 Ltr cooling problem..

I have changed the impeller in the lower unit

See if this stuff helps any . . . You haven't posted your year model; your cooling flow may be different to the exhaust manifolds and risers than shown.

There are also engine issues that can cause overheat, but yours happens quickly and doesn't sound like you are talking under load (not in gear and at speed?) . . .

 

[chiefalen]

Re: 350 Mag 5.7 Ltr cooling problem..

Welcome aboard !

You have a heat exchanger ? Known to get clogged up.

When was the last time you looked at the risers ? They get clogged up your gonna overheat.

And finally when you do have the risers off, both of them look and see if it had a flapper, and it broke off and clogged your exhaust.

 

[chiefalen]

Re: 350 Mag 5.7 Ltr cooling problem..

Oh you got a manual?

 

[jerryjerry05]

Re: 350 Mag 5.7 Ltr cooling problem..

More info please!!! Year,salt or fresh water.Was it overheating before you worked on it? Any info would be a help.
When you replaced the impeller did you align the water tube.Was the old impeller remove in 1 piece or chunks.
If the boat is older than 10 years you might need risers and manifolds. Jerry

 

[chiefalen]

Re: 350 Mag 5.7 Ltr cooling problem..

He said he changed the impeller in the out drive. Did he do it right don't know.

You could try pulling the long hose at the t-stat put water to the drive and see if your pumping water to the t-stat. Bye running the motor.

If it's pumping good there than it's farther along the clog.

You do know never to start that boat without water going to the drive not even for 5 seconds.