DF 200/225/250 impeller shred

[Still Floatin]

Hi all. I am a Pensacola, Florida native new to the forum but otherwise oldy and moldy . This looks like a nice community and I hope to have something useful to contribute.

At the moment I have a knotty DF 200 overheat problem that goes like this: late last fall the heat alarm sounded so I limped back, dropped the lower unit and found a shredded impeller. Changed out impeller, SS cup & o-ring. I don't think I replaced the pump housing itself. During my spring cleanup & checkout I find that the overheat persists when idling in the yard w/ ears. Telltale stream runs steady but seems a tad weak. My first reaction was *Awk! The shredded rubber chunks got into the cooling galleries so now I have to do a TEARDOWN!*

Not sure whether this engine series is prone to the exhaust leak forces cooling water out before uptake problem mentioned in another thread. If so then I would like to understand more. However, my first guess says that's not the problem bc exhaust behavior hasn't changed since I got the engine in 2009 (its a 2005 unit).

So I have three questions:

1. 1 -- Does a shredded impeller often result in a blocked cooling system?
   2 -- If so, where are the most likely places for rubber chunks to jam -- for instance, behind the water pressure valve?
   3 -- Or, in your opinion, is it a different problem?

Thank you in advance for your sage advice. Its late and I was fishing last night (a bust) so I'll turn in and check back in the am. Gnite all.

[Bamahemi]

I would drop the lower and flush from power head port to force debris out bottom, also remove thermostats, as far as engine being prone to the exhaust issues hopefully someone else will chime in.

[Danny1960]

Possibly thermostat prob stuck closed quite common in automotive applications when engine has been severely overheated Good Luck(

[Still Floatin]

Oh, fudge ...

Thank you for the replies. Yes, I already pulled the thermostats and backflushed from the top. Did not trap any rubber bits at the lower end so they must be jammed in the galleries. My ace mechanic brother-in-law says, "I'm sorry for ya ... but you're just gonna have to clean it out by hand, bubba!" I would slap him if he was a little weaker.

[artdf175]

the 175 has a fresh water flush port on the Port side..
the cooling water from the pump is piped up to just below where there is a pressure relief valve.. should definitely check this area as debris is known to keep the valve open
then behind the fresh water flush port.. cooling water moves through this passage to the power head..
carefully..remove the bolts and check behind this cover plate
there is a relatively small hole for water to advance up to the power head..
and for both of these areas, it would not hurt to flush them out
I would have all three removed, which includes the thermostat, for flushing
and while you have that flush port coverplate remove.. check to see that the wall does not have any corrosion .. the internal exhaust port is on the backside of mine and it had a hole in it dumping cooling water into the exhaust and overheating the engine at idle..
Art
one other thought.. while you have the pressure relief valve out.. put the ears on and run the fresh water to make sure it is getting up the cooling tube to that location..

[briscoe]

I had similar issue

I replaced the SS housing around the water pump and the impeller and had some gasket sealant get in one of my small hoses. I ended up locating it by using the hose routing layout from OEM manual. I took off sides and top and ran motor with muffs at idle. Removing one hose at a time I found the supply hose that was plugged, as it had no flow. Shutdown engine and blew it out. No overheat issues since. As I remember it was the hose that went to the top of the engine block on the starboard side. The one above the fuel rail (I think).

Good luck. It's not a big job. Although I did enlarge the page size of hose route from the manual, on a copy machine.

[Still Floatin]

Good advice ...

Thank you Art and Briscoe for your excellent suggestions. Fortunately I haven't yet started this job. Wife laid down the law - the usual complaint - "Our house looks like a junkyard ... etc, etc" so I've been cleaning up for days. Looking forward to sleeping in the house again

Art, the DF200 apparently has a different layout but I will try all your steps. The OEM manual doesn't have a schematic of the cooling water galleries themselves, only the hoses. But all the things you mention seem to also be on my engine, so it looks like the first thing to do is to remove the cover of the water pressure relief valve and make sure the cooling water isn't dumping into the exhaust pipe.

Briscoe, I did not think about testing the hoses ... I must be losing brain cells. Your hose-by-hose testing scheme should save me some work.