Overheating after raw water pump rebuild

[Leaky Rear]

Original issue was a piece of impeller stuck in the the bypass hole of thermostat housing.
Exhaust manifolds overheated , and I smelled it right way. Broke things down , found the impeller in pieces. Heavy black grease all around the raw water pump.
So rebuild raw water pump went smooth , and put new impeller tried to flush out all the pieces and put back together , priming the system with many gallons of water . The hose to each left and right exhaust manifold , the water poured thru seemed to go out the back so I thought not clogged . Air blew through so i expected hoses clear.

Took boat out. Perfect operation for a short time
Then exhaust manifolds overheated again , while cruising. Couldn't smell with engine cover on . Motor and manifolds got extremely hot - basically stinking and would burn your hand ( gauge still showed 175) but this motor /manifolds has always been cool to touch while running .

So Ive overheated the boat , and got back on my lift -dry dock.
Terrible scraping sound while cranking . Motor will still run , but I shut off right away.

I expect removing the thermostat housing again may find more blockage by small pieces of impeller. Sure aI can pull the raw water pump and inspect and see how it looks .
When Id flushed the block heads manifolds previous to putting together- Id forgot the water path starts at the I/O intakes holes.
I can imagine impeller chunks floating all around water jacket ect waiting to put me through this again, the overheating.

There may be a pice of impeller floated back there , towards the I/O
How to go about troubleshoot these issues.
1. locate source of scraping noise without possibly more damage to motor /drive
2 Overheating but not display more than 175 on gauge Motor is not seized and motor oil is still clean looking
3 .how to get ALL the old pieces of impeller out of the raw water system- drive block and heads outdrive ...

I am asking a lot here , any help appreciated.

 

[Sparkinator]

What drive? Year? My 95 SX Ford 5.0 overheated when the impeller failed. I found pieces all through the coolant passages. Also found melted flappers (no longer used on my model) in my lower unit exhaust.

Mine got so hot it melted the exhaust boots. I had to replace the carburetor too. High heat can do a lot of damage to almost anything on your engine.

Change engine oil and dig into all your hoses and thermostat. Check lower unit exhaust. Take hoses loose from discharge side of raw water pump and make sure you have good flow through each hose. Keep unhooking hoses until you know each hose has flow and any impeller bits were flushed out.

Try to pinpoint grinding sound after changing oil. Get in engine bay while someone turns the engine over.

Good luck.

 

[Lou C]

those overheats can do a lot of hidden damage...example...there are grommets that seal the water transfer tube that takes water from the lower to the upper gear housing, hot exhaust going thru that area with out water can melt them. I had that, and melted flappers from a bad overheat.

 

[Leaky Rear]

Hello members . Those are rock solid suggestions , exactly what I needed to move forward.

Post #1 , I have a 2000 Volvo Penta 5.0 SX GL PEFS

I was in a hurry to save the boating season . Now that my boating season is likely scrapped , I can plug away on the described above repair until rains start ( all fall) . I was pretty upset after the incident. I feel lucky the rubber exhaust pipes did not melt , although everything will need a close look .

My absence has been due to health issues , hope you all understand.
I see its been a few weeks since I posted.