2005 Mercruiser 5.0 mpi overheating

[tcorm]

Have a post in another forum (different site), but no responses. Thought I'd try here...

Have a 2005 MC 5.0 MPI (0w063211)- 285 hours with Alpha 1 Gen. 2 (0w549135) – seawater cooled. Over heating issue.

Here’s the story – starting it for first time after winterization. Changed oil and fuel filter. Hooked up the hose and muffs. Took some time to start, but finally ran smoothly. Exhaust became smoky (not immediately). I thought it was just burning off the fogging oil, but after a few minutes, temperature climbed, and the alarm went off. I immediately shut her down. I’ve never changed the impellor (owned for two years) – so dropped the lower half of the outdrive. I did notice the upper seemed warm. The impellor seemed fine but changed it out with a new one and a new body. Filled it with fresh fluid and started it again. Did away with the muffs and filled a huge storage container with water – big enough to submerge the lower unit up to the water intakes. Started it and overheated again. I don’t think any water is reaching the engine. I removed and tested the thermostat – checks out good. When doing so, no water poured from the cooling hoses. In an effort to move up stream, I then removed the hose from my power steering cooler and no water there.

Just not sure how to proceed. I don’t know if I have blockage, my impellor key fell off, or worse. Hoping for some methodical troubleshooting.

Thanks,

T

 

[Bt Doctur]

The pump wont suck water , it moves water Simply covering the intalkes destroys impellers. Water level must be 3 inches above the cavitation plate

 

[alldodge]

Howdy
With muffs on the drive and water turned ON full stream, you can see water spilling out all around the muffs. When the motor starts does the water spilling out reduce any?

 

[Searay205]

I had a similar experience with rectangular ear muffs. Oriented them incorrectly and the muffs were crushed against the intake grates and would not allow water into the intake grates. rotated muff ears and zero issues. I did replace the perfectly good water pump impeller thinking it was the issue

 

[Rick Stephens]

Probably melted the new impeller trying to run it in a bucket.

 

[tcorm]

Thanks for the responses.

Wow - hell of a kick in the you-know-whats, thinking I was doing the right thing. Thanks for the info everyone. Looks like I'm going to check the impellor out again. I'll report back.

Question - if water is not "sucked" into the intake, how does it cool when idling (not moving) - or it doesn't?

T

 

[Searay205]

try some round flush ears. when idling and sitting in the water the level is above the impeller no need to suck when submerged

 

[Rick Stephens]

Pretty much all marine cooling pumps are vented to allow them to fill and vent out the air. Next time you have your pump apart look for the small passageway going from the pump base to the outside cavity. When submerged, the pump fills up with water. When on muffs, the water is under pressure and squirts out the vent hole. The pump cannot create any suction at all.

 

[tcorm]

Dropped the lower leg again. Impeller was fine. I ended up doing it all over. Confident it is correct. I've done these before.

Started again with new hose and muffs. Solid coverage of the inlets and plenty of water volume (but, not too much). Same thing - OVERHEATED!

Could something upstream be preventing water from reaching the thermostat. I do have power steering, and I think that cooler is where the cooling water first enters the engine bay? Not sure where to go from here, except maybe the repair shop..

 

[alldodge]

Remove the hose going to the thermostat housing from the drive. Connect muffs and start the motor, then let us know how much water was seen

Also is this a 1, 3 or 7 point drain system?

 

[tcorm]

Ok - SOLVED! Can't say for sure what solved it, but here are some of the things I did or might have helped - in this order:

1. Increased my water volume -(might have)
2. Sprayed back through the feed that enters the PS cooler and saw water exit my inlets.
3. Took the belt off and inspected the alt. pulley and circulator pulley. Both seemed good. It's possible when I reinstalled the belt I tightened it?
4. Opened the port riser drain - "alldodge" - I believe I have a 7 point drain system (lots of plugs!). Ran it and observed water flowing.


Tried again and idled for over 5 minutes with the temp pegged at 174. Not a degree more.

Knowing that this all started out of being winterized, I do not believe anti-freeze was used by my mechanic. Seems that the engine was simply drained. Is it possible that there was air in the system that prevented water flow, and not until I opened a drain and ran the engine briefly did it expel that air pressure and allow water to get to the thermostat?

After 50 years, you'd think I'd change my ready-shoot-aim approach to these types of things. Someday...

Thanks to everyone that responded.

FYI - still don't have a single response in that other "boat hull" forum

T

 

[Searay205]

possible thermostat was stuck closed or wouldn't open all the way.

 

[alldodge]

Many including my self do not use antifreeze, just drain everything during winterization. Air would not be the issue, water will displace it

When running on a hose, the garden hose should be on max flow