I am in the process of rebuilding my MD3B. THere is a blockage in one
of the exhaust manifold's passages which I'm pretty sure is a piece of
impeller. I've tried compressed air, coat hangers, and dental tools
but I can't get it unblocked.
Does anyone know anything else to try? I've thought of heating with a
MAP gas torch, or baking it.

Any ideas?

Which passage is it? One of those passages is supposed to be blocked.


David
S/V Nausicaa

It's the exhaust manifold passage between the small inlet port on the
head closest to the flywheel and the manifold water inlet. As you
probably know, the cooling water enters the manifold on the bottom of
the manifold between the aft and middle heads. There are three small
holes where the cooling water leaves the manifold and enters the head.
There are three large rectangular holes where the cooling water
re-enters the heads, then leaves via the thermostat. (At least that's
how I think it works. The aft and middle ones are very clear (dedspite
being physically smaller).

I had the thought to put a pressure gauge somewhere on the cooling
circuit to monitor the cooling water pressures/impeller status.

-Ryan
S/V Whale II

"dbraun" wrote in message alkaboutboats.com...
Which passage is it? One of those passages is supposed to be blocked.


David
S/V Nausicaa

I was able to clear out the blockage using a 20:1 solution of muriatic
acid, and a coathanger. I poured the acid solution so that is went in
to the manifold, through the area with the partial blockage, then out
of the manifold. There was a lot of fizzing, but it got better and
better until it reached a point where the flow seemed reasonable,
perhaps 50% of the other inlet passages. This is up from around 5%.
I ran a great deal of water through the head to neutralize the acid.
Now if I can only find a ring compresser which opens up after use to
allow me to insert the pistons, which are still connected to the
crank, into the jugs.

(RyanN) wrote in message . com...
It's the exhaust manifold passage between the small inlet port on the
head closest to the flywheel and the manifold water inlet. As you
probably know, the cooling water enters the manifold on the bottom of
the manifold between the aft and middle heads. There are three small
holes where the cooling water leaves the manifold and enters the head.
There are three large rectangular holes where the cooling water
re-enters the heads, then leaves via the thermostat. (At least that's
how I think it works. The aft and middle ones are very clear (dedspite
being physically smaller).

I had the thought to put a pressure gauge somewhere on the cooling
circuit to monitor the cooling water pressures/impeller status.

-Ryan
S/V Whale II

"dbraun" wrote in message alkaboutboats.com...
Which passage is it? One of those passages is supposed to be blocked.


David
S/V Nausicaa

Use an adjustable clamp that is in the correct size range.After the rings
are compressed and the jug is slid on unscrew the clamp all the way and
presto its off. The clamp will work even if all the piston rings are not
covered.Just make sure the clamp is on all of them enough to compress all
the rings.
I've used this method on various engines from boats to airplanes.

"RyanN" wrote in message
om...
I was able to clear out the blockage using a 20:1 solution of muriatic
acid, and a coathanger. I poured the acid solution so that is went in
to the manifold, through the area with the partial blockage, then out
of the manifold. There was a lot of fizzing, but it got better and
better until it reached a point where the flow seemed reasonable,
perhaps 50% of the other inlet passages. This is up from around 5%.
I ran a great deal of water through the head to neutralize the acid.
Now if I can only find a ring compresser which opens up after use to
allow me to insert the pistons, which are still connected to the
crank, into the jugs.

(RyanN) wrote in message
. com...
It's the exhaust manifold passage between the small inlet port on the
head closest to the flywheel and the manifold water inlet. As you
probably know, the cooling water enters the manifold on the bottom of
the manifold between the aft and middle heads. There are three small
holes where the cooling water leaves the manifold and enters the head.
There are three large rectangular holes where the cooling water
re-enters the heads, then leaves via the thermostat. (At least that's
how I think it works. The aft and middle ones are very clear (dedspite
being physically smaller).

I had the thought to put a pressure gauge somewhere on the cooling
circuit to monitor the cooling water pressures/impeller status.

-Ryan
S/V Whale II

"dbraun" wrote in message
alkaboutboats.com...
Which passage is it? One of those passages is supposed to be blocked.


David
S/V Nausicaa