Outboard guy helping out on a 2001 5.0 MC heat issue, Questions on troubleshooting

[rothfm]

Experienced outboard person here, in beginning stages of assisting a friend that has a 2001 5.0 EFI MCruiser, fresh water cooled.

This season he is experiencing a rising heat/with RPM issue. I'm suggesting the steps for him to start with, listed below. Last season he did the mani's and risers as the history was unknown. Temps were fine last season after that work- steady at 160, all speeds.

The impeller was just removed and small areas of each vane was "eaten away" (small spots).
Currently Idle is about 170 in the water, with a 160 Stat...Upon planning off it climbs toward 200, and will lower again when backed off.

This setup has the Outdrive water path Blocking Plate in place, and uses a Thru-Hull intake with Belt driven water impeller.

Suggesting to him:

* Remove Exchanger for visual inspection, cleaning-looking for debris from last impeller
* Open Raw water side intake hose, and introduce water after the impeller, ensure good volume comes out the transom
* Open the coolant/antifreeze side, introducing water thru the block, ensure proper volume comes out.
* Remove and check any Power Steering, Cool-Fuel exchangers, if above flow-checks yield any flow restrictions


My big questions is THIS:

He has a "Hesitation" issue upon acceleration...If you hit the throttle it "bogs and hesitates" but will eventually catch up and run pretty smooth. If you accellerate lightly it does fine. I'm wondering if this "Bog/hesitation" issue can be related to the Heat-up problem? Meaning a vacuum leak also causing higher combustion temps, and bogging???

Is there a good way to test for bad head gasket/cracked head or block?

 

[Bondo]

The impeller was just removed and small areas of each vane was "eaten away" (small spots).

Ayuh,..... The raw water pump needs to be rebuilt,.... Any imperfection is too much,....

The boggin' issue,..??

I'd check the Contents of the fuel filter for anything but clean fresh gasoline,....
Then twist on a new filter, mostly pre-filled,...

 

[kenny nunez]

There is a litmus test that can be done to check for combustion by products in the cooling system that can be purchased at various auto stores.

 

[rothfm]

Thanks.


Think he solved the heat issue....From 2 impellers ago, fragments collected at the end of the raw water line at the Exchanger. Cleared out, and so far Temps sit at 160-165 on the Thru-Hull hose attachment. Water testing is pending.

Still has the bogging issue, cant really get a handle on possible causes. If you accelerate gently it doesnt bog, and sounds good.