Volvo duoprop exhaust question/problem
 

Hello. I'm not sure if this is really a problem or not. I have twin
4.3L Volvo Duoprops. I noticed that at idle, at the dock, one engine
is bubbling out exhaust gas (under water of course) as I think it
should but the other looks like it is hardly bubbling at all. On
further inspection, I noticed that the exhaust is not coming out of the
two rectangular rubber flaps near the bottom rear of the outdrive
(above the props) but rather, the exhaust is bubbling up around the
steering helmet area.

I donned my swim mask, shut off the engines, and dove down to look for
what I expected would be a loose exhaust bellows clamp (all bellows
were replaced new this spring). Unfortunately, the bellows were still
on all the way and the clamps were tight.

I didn't want to run the engine while I was underwater looking around,
and the outdrives are tucked nicely under the swim platform so I really
can't see what's going on.

If I increase the idle speed to around 1500, the exhaust comes out the
rubber flaps as it should, or if I tilt the outdrive up to 10 degrees,
again the exhaust comes out the rubber flaps as I think it should.
Only at low idle, with outdrive at zero degrees, does the exhaust stop
coming out the flaps and comes out near the steering helmet.

This is a strange one for me. I don't even know if there's something
wrong. Engine runs perfect, good water temp, good smooth idle. Any
ideas? This is bugging me but I'm not ready to haul it out to have the
marina check it out for hundreds of dollars if you know what I mean. I
don't have a trailer.

Thanks in advance,

BD