5.7 mercuriser overheating

[greno]

What you describe is normal for the water flow on cups.
You need to account for the flappers.
I stuck a tiny camera up the exhaust outlet in the transom and could see mine. A cellphone that isn't too big might also work.

 

[lloane]

Can I run a long rod down from the top and a see if it's not opening and push it open?

 

[greno]

Yeah, you're going to need a buddy and a mirror to do it.
One works the rod while the other works the mirror through the exhaust outlet.
Be careful. I did this with a coat hangar and got the thing stuck in there. Took me half a day to get it back out.

 

[lloane]

I have a drain router I would use for it, but if you see the amount of water and exhaust that was coming out, I highly doubt the flappers are stopped up.

 

[greno]

If they are preventing full flow you're going to overheat and lose performance as well.
These things can break off, get stuck. Even without breaking off they can get stuck partially open.

 

[AShipShow]

Greno, that doesn't sound accurate... if the shutters are restricting flow that much, then the engine would also be stumbling from a restricted exhaust. Plus, if the water can't get out faster than its coming in it would flood the exhaust.

loans, have you tried putting your thermostat in hot water to verify its opening fully?

 

[greno]

Mad Props, read the whole thread. He took the thermostat completely out and there was no change.
From experience of having broken shutters I can tell you that they will overheat the engine and they will drop RPM.
And yes, water flow looked normal but there was enough exhaust restriction to cause a problem.

 

[Scott Danforth]

as stated in your other post, check water flow

you should have enough water flow at 1500 RPM to fill a 5 gallon bucket in under 18 seconds

one manifold and elbow will always be 20-30 degrees warmer. depends which way the boat is leaning. lowest manifold runs cooler

 

[Lewis1111]

Had a similar issue with a slightly warped head, took me a while to figure it out. Must have been sucking air. To rule out the drive unit or any air leaks from the water pump remove the drive unit and put a hose attached to your garden hose up the water inlet through the gimbal ring and run the engine. This will rule out any issues with the drive unit or water pump repair you did.