470 overheating

[foste1cc]

I successfully got my 470 running after a couple years of tinkering around with carb and ignition issues. I put a brand new thermostat in it last season, since I new I had the time and it's a cheap part.

There's water coming out of my sterndrive while the muffs are on, so I'm quite confident I'm pumping water (New lower unit water pump last year)
What's the next thing I should check?

It over heated about 3-4 minutes after starting and idling. then the cap on the reservoir tank blew off.
3 seasons ago, I remember having this boat on the water for hours and it was fine. Still has the 3" heat exchanger (which I know... I should upgrade to the 4".. but can that really be my cause?)

 

[Bondo]

It over heated about 3-4 minutes after starting and idling. then the cap on the reservoir tank blew off.

Ayuh,........ What was the temp, at that point,..??
The sentence above, leads me to believe there's probably compression, leaking into the cooling system, aka: a blown head gasket,......

 

[foste1cc]

I want to say it was at 180+ when it happened.

 

[Breezeworks]

Head gasket could be right. Totally corroded exhaust elbow stopping up exhaust, maybe. When impeller changed, was old one broken?

 

[foste1cc]

Yes, the old impeller was in dozens of pieces when I changed it out.

Is there a way to check if my head gasket is blown without tearing it all apart?

I'll look into the exhaust elbow* today and inspect it.

 

[Scott06]

Yes, the old impeller was in dozens of pieces when I changed it out.

Is there a way to check if my head gasket is blown without tearing it all apart?

I'll look into the exhaust elbow* today and inspect it.

You could pressure test the cooling system with an automotive style cooling system pressure tester. The antifreeze side of you engines should hold pressure.

Those engines are known for the cam driven water pump to leak AF sometimes into the oil

 

[foste1cc]

1st thing I just did was pull the front cap on my heat exchanger. This was all in the one section where the cold water enters. Before I dig into the exhaust elbow, would this seem like the cause of my issue?

Old impeller pieces.

 

[Bondo]

1st thing I just did was pull the front cap on my heat exchanger. This was all in the one section where the cold water enters. Before I dig into the exhaust elbow, would this seem like the cause of my issue?

Old impeller pieces.

That could be a reason for heating up so fast, but doesn't explain blowing the cap off,......

 

[Scott Danforth]

the 470 doesn't do well if the temp got over 190. the aluminum open deck expands so much faster than the iron head leading to compromised head gaskets

based on the pic, it doesnt look like the 4" updated heat exchanger. you may want to look into that. the 4" will keep the motor cool for a short bit of time after the impeller goes

drain the coolant side, then pressure test to 15 psi. should hold forever.

if it doesnt hold, listen for the hissing and fix the issue. its either head gasket or the seals on the cam snout that drives the water pump.

the captured impeller bits means the impeller hasnt been serviced regularly.

I would recommend a pressure gauge for the raw water side

 

[foste1cc]

I'm going to give it a driveway test within the next couple hours and just monitor it carefully and be ready to kill it if things start to get too hot.

I'm about ready to throw this boat in the trash, so I'm not too worried about hurting it much. It's just been a giant paper weight since I got it...

Living the good life - the boating dream....

 

[Scott Danforth]

Living the good life - the boating dream....

However the 470 puts the life on elm street...... and Freddy Krueger is in the dream

 

[foste1cc]

Thought I'd not only follow up on this post, but admit to my mistake.

Just because you can see coolant in the recovery tank, doesn't mean you actually have enough coolant!!

I feel like such a noob...
Added a coolant/water mix until I could see some in the reservoir tank. Started her back up, and she never got over 140F after 10 min.

 

[ROY WILLIAMS]

Thought I'd not only follow up on this post, but admit to my mistake.

Just because you can see coolant in the recovery tank, doesn't mean you actually have enough coolant!!

I feel like such a noob...
Added a coolant/water mix until I could see some in the reservoir tank. Started her back up, and she never got over 140F after 10 min.

ROY WILLIAMS 1978 ENGINE MCM470 COOLANT ANTIFREEZE 50% DISTILLED WATER 50%. ENGINE COOLANT ANTIFREEZE ENGINE! NICE !
THE cadet foste1ce 470 engines rusted of the water!

 

[ROY WILLIAMS]

Yes, the old impeller was in dozens of pieces when I changed it out.

Is there a way to check if my head gasket is blown without tearing it all apart?

I'll look into the exhaust elbow* today and inspect it.

MCM470 ENGINE WATER DAMAGED IT!
NO! ANTIFREEZE-DISTILLED WATER ENGINE PUMP, HEAD GASKET, EXHAUST ELBOW.