Help! Mercruiser 4.3 over heat, I am stumped.

Hello, all, I am ready to kill this thing. I have a 2008 4.3 mercuiser raw water cooled boat with 20 hours on it nada flush pro installed. The boat sat for a while and I have done the following.
1. Replaced impeller
2.after running on ears it over heats.
3. Water pours out of one side on the transom out side the boat, but a steady trickle out of the other.
4. Took out plug on bottom of circulation pump and ran it on the flush housenhookedmto transom, bunch of black stuff came out.
5.removed thermostat
6. Removed circ. pump, flushed, and flushed passages on both sides of block where circ pump mates to.
7. Have run engine on both flush hose and muffs, still overheats
8.disconnected all hoses and flushed and checked for obstruction
9. Disconnected circ hose at thermostat, started engine and verified water flow hose at thermostat
It seems like one side or the other over heats, like water is not being evenly distributed. I checked the ball things that got risers,they move freely. Any help appreciated.

Re: Help! Mercruiser 4.3 over heat, I am stumped.

What outdrive do you have?

Re: Help! Mercruiser 4.3 over heat, I am stumped.

Don S said:

What outdrive do you have?

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Alpha

Re: Help! Mercruiser 4.3 over heat, I am stumped.

Outside of the obvious causes, a missing impeller keyway or broken shaft in the drive. I`d check the circulating pump for a broken shaft. simply remove the back cover and look. Or remove the drive and insert a water hose from a washing machine cut in half in the inlet port on the transom.

Re: Help! Mercruiser 4.3 over heat, I am stumped.

Bt Doctur said:

Outside of the obvious causes, a missing impeller keyway or broken shaft in the drive. I`d check the circulating pump for a broken shaft. simply remove the back cover and look. Or remove the drive and insert a water hose from a washing machine cut in half in the inlet port on the transom.

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Water flow was verified from the impeller on drive by disconnecting at thermostat housing while running motor. Circ pump was taken off and verified as to free movement and intact.

Re: Help! Mercruiser 4.3 over heat, I am stumped.

Biminibrad said:

The boat sat for a while and I have done the following.
1. Replaced impeller
2.after running on ears it over heats.
3. Water pours out of one side on the transom out side the boat, but a steady trickle out of the other.

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Did it over heat before the new impeller or after the new impeller? What name brand impeller did you install?

Re: Help! Mercruiser 4.3 over heat, I am stumped.

Biminibrad said:

Water flow was verified from the impeller on drive by disconnecting at thermostat housing while running motor. Circ pump was taken off and verified as to free movement and intact.

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You'll want to check for air bubbles using a clear water hose.

Re: Help! Mercruiser 4.3 over heat, I am stumped.

7. Have run engine on both flush hose and muffs, still overheats

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If you ran the engine without muffs while using the flush hose, you need a new impeller.

The flush hose is for flushing without the engine running.

Re: Help! Mercruiser 4.3 over heat, I am stumped.

Circ pump was taken off and verified as to free movement and intact

Without removing it and shaking it or removing the back plate, you`ll never know if its broken.
Removing the drive and using the hose will isolate the trouble to drive or engine.

Re: Help! Mercruiser 4.3 over heat, I am stumped.

Biminibrad said:

3. Water pours out of one side on the transom out side the boat, but a steady trickle out of the other. It seems like one side or the other over heats, like water is not being evenly distributed. I checked the ball things that got risers,they move freely. Any help appreciated.

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Is your boat/engine leaning to one side? I've noticed mine running on muffs if not fairly level that one riser will run hotter than the other. If I level it out....magic! both risers feel identical in temp. Also after being underway and stopped, one riser may be hotter than the other and any given day it could be the other way around, or sometimes they are both equal in temp to the touch. I figure it as just the way the load is riding on that particular day.

4. Took out plug on bottom of circulation pump and ran it on the flush housenhookedmto transom, bunch of black stuff came out.

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Bunch of black stuff??? Can you elaborate?

Re: Help! Mercruiser 4.3 over heat, I am stumped.

tahoejag said:

Is your boat/engine leaning to one side? I've noticed mine running on muffs if not fairly level that one riser will run hotter than the other. If I level it out....magic! both risers feel identical in temp. Also after being underway and stopped, one riser may be hotter than the other and any given day it could be the other way around, or sometimes they are both equal in temp to the touch. I figure it as just the way the load is riding on that particular day.



Bunch of black stuff??? Can you elaborate?

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Yes, back cover of circ pump was taken off, and yes it overheats after a new impeller was put on the out drive. As to need ing a new impeller, flush pro post say you can run the engine while on the flush hose as water goes to impeller as well?

Re: Help! Mercruiser 4.3 over heat, I am stumped.

Biminibrad said:

As to need ing a new impeller, flush pro post say you can run the engine while on the flush hose as water goes to impeller as well?

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All the information on the Flush pro shows it installed before the pump, with an Alpha outdrive you would have to install it after the pump and that just isn't going to work.
All the information shows it used on a straight inboard, not an IO with the pump in the drive.

http://www.perko.com/images/catalog/pdf/flushpro.pdf

Sounds like you better check your impeller again.

Re: Help! Mercruiser 4.3 over heat, I am stumped.

Sure would be nice if they gave us all the information in their first post.Especially on how they have hooked up various components.
Still, pull the drive and test with a remote connection to isolate engine or drive.

Re: Help! Mercruiser 4.3 over heat, I am stumped.

You say the engine is overheating, is this because the gauge says so, or the alarm goes off?
Have checked to see if the engine is actually overheating using one of those IR temp guns?

Re: Help! Mercruiser 4.3 over heat, I am stumped.

Don S said:

You say the engine is overheating, is this because the gauge says so, or the alarm goes off?
Have checked to see if the engine is actually overheating using one of those IR temp guns?

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Ok, problem solved. It appears that pieces of the previous impeller melted and clogged the thermostat housing passage. This caused water to not go to the circ pump and in to the block but to pour thru the manifold check valves. Yes the boat was leaning 2 inches, causing water to come out only the port exhaust transom hole. The flush pro is hooked up to the main line coming from the transom plate/ impeller, so I do not think it would damage the impeller. Thanks for the input.

Re: Help! Mercruiser 4.3 over heat, I am stumped.

The flush pro is hooked up to the main line coming from the transom plate/ impeller, so I do not think it would damage the impeller

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There is no water going to the impeller when you are using the flush pro connection. No water to the impeller = impeller damage.

You may not notice it as much on muffs being a Gen II drive, but under load out on the water is going to be another story.