Took the boat out today. I got 300 mtrs and the overheating alarm sounded. A quick
look showed me a bilge full of water and a noisy engine.
I bought the boat with one of those plastic exhaust waterlocks fitted. It's a Vetus type LP
made in Holland.
The inlet and outlet are the same size..Inch and Three quarter. (1-3/4"). Now the outlet fits
the flexible pipe to the hull fitting but the inlet doesn't fit the hose from the engine.

The engine exhaust elbow (Buhk 10 HP) is 2 inch with a 2 inch flexible hose to the inlet which
is 1-3/4". There is the remains of some black hard substance that has disintegrated leaving a
gap between hose and inlet pipe allowing the exhaust water to end up in the bilge.
I could get a new waterlock from Whitworths (2 inch) which will fit the inlet hose but not the outlet
I can find no reducers of the size I need. I have thought of wrapping fibreglass tape around the inlet
to make it up to 2inches, but apart from that I'm stumped.
Any Ideas welcome.

Sam , I had a Mk1 Top Hat with a BMW d7 (Be in trouble motor) I rebuilt this thing and learn't a hell of a lot about little diesel engines to a stage that now I'm dangerous around one !! The manifold had the same problem with pipe diameter so I sleeved a smaller hose inside the bigger hose and a couple of hose clamps to seal it tight and that worked .Copper tube from a plumber and braised or spread wider is another idea, cheap !
I think you'll find your black substance is carbon/soot from the engine ,you know the black stuff that comes out the exhaust when you run the engine to hard.

Cheers Bear

Would this help ?
www.whitworths.com.au/nanni-diesel-exhaust-water-lock-40-50mm
i have seen others with a wider range of steps

So I took the whole kit and kaboodle to whitworths to see if they had anything that I could
use to get over the problem.
I had a look at the Nanni system and while it solved the inlet side 2" to 2" it shifted the problem
to the outlet side 50/40 mm to 13/4", one too big and one too small.
So I checked out the exhaust hose sizes and found the smaller dia just fitted inside the 2" dia.
Grabbing the removable inlet fitting from the Vetus I tried pushing it into the smaller dia hose,
no go but hey if I soaked the hose end in boiling water I might just be able to push it on. I dont
know if this exhaust hose softens up but it's worth a try.
So I got a 4'' long piece and bought it home. WhooHoo. It worked. So guys, never say die 'til a
dead horse kicks you. So now I've got the small dia pushed onto the fitting and the 2" dia pushed
over the top of it. It's a nice tight fit and with the hose clamp on tightened with my biggest
screwdriver I don't think it's going shift.
Thanks for the input Fellas. Much appreciated.

Yes. That's a good point Yara. I have to refit the exhaust system before I can check everything else.
Is it possible that the cooling pump went bung and caused the exhaust problem and the water in the
system leaked into the bilge via the now non fitting hose from the engine to the vetus???.