1965 6hp CDL-22 - no telltale with thermostat installed

[sludgeguy68]

OK this one has got me stumped.

I replaced the water pump with new t-stat and related gaskets last year, it ran great for summer and fall months. Started it up this year to find my new powerhead gasket leaking water in the front center, maybe I didn't torque it down enough or didn't use gasket sealer... anyway, so I put it back together with a new gasket and there's a good stream from the telltale for a second or two, then it's just exhaust.

Note this is the factory "telltale" that spits water out the back of the leg.

When I run it without the t-stat installed, it pumps water like a champ. What gives??

Impeller still looks good. Tested t-stat and it opened before water came to a boil in a pot. I remove the cylinder head and all passages looked clear, blasted air and water through passages in the block and they all exited another hole. Passages are clear in the channels under powerhead and telltale pipe. I put it back together, got the same result.

I ran it with t-stat cover off and water comes up without issue. Water level in barrel is high and putting it in forward gear doesn't help. Blasted water up the water tube with the lower unit off and it came out the telltale fine.

I don't want to run it too long without seeing any water circulation, nor do I want to run it without the t-stat. Thoughts?

 

[F_R]

There are two water flow paths through that powerhead. Water always flows through one path regardless whether t'stat is open or closed. The other path flows only when t'stat is open.

So what you probably have here is the path that should always flow is plugged up. The most common place for that is exposed by pulling the cylinder head. Actually, it is quite common in motors run in salt water. Of course, it can happen in fresh water too, just not as common.

 

[sludgeguy68]

Thanks, AFAIK it's a freshwater motor but a bit crusty so who knows. Two water paths make sense.

The only questionable part of the water path I can't get to is in the exhaust jacket, whose bolts have not moved in a very long time and I'd rather just leave in there... however, I imagine this area is part of the "always cooled" path and could be suspect if the cylinder head water is diverted before that point.

I guess I'll pull the powerhead again... if someone can point me toward the common problem area it would be appreciated, thank you.

 

[oldboat1]

Think I would pull off the head cover and resurface it (DIY job requiring some wet/dry sandpaper and a hard surface). Probably will want a new head gasket. Torque in circular fashion, starting from the inside.

When the head is off, check water passages incl bypass passage. Salt or sand can be a problem -- also critters (can block tell-tale).

 

[F_R]

Arrow points to the restrictor where corrosion commonly causes blockage. Water flows from there to the thermostat cavity ABOVE the thermostat and then down the backside of the head and out the exhaust. This water does not pass through the 'stat, and flows anytime the engine is running.

Second flow path enters the bottom of the thermostat cavity, BELOW the thermostat. 'Stat must be open for this flow to happen.

 

[sludgeguy68]

Just wanted to post an update in case someone may have the same issue.

I cleaned out the exhaust jacket (found some stones in there), replaced the inner plate that had warped, and re-checked the water passages under the head. Put it back together with same result - strong telltale for a minute then just exhaust. Tried with and without t-stat, didn't seem to matter this time.

I was convinced by now that some kind of air pocket was forming in the barrel, perhaps from the exhaust... so I ran it on the boat, and lo and behold the telltale was back to normal and cooling properly.

Maybe my trash can is too small or narrow, or the issue is exacerbated with the long shaft, but for some reason it does not want to pump water in the barrel (even with a very high water line). Hope this helps someone out there; thanks for the help along the way!

 

[oldboat1]

Interesting. Sounds like the water supply issue might be down in the intake — maybe cleared out now by running in the the lake. Could check the intake screen underneath the plate, and pull off the cover above the plate on the side. Do a little careful poking and flushing.

 

[racerone]

Test with water level 6" above the pump.