Last year I bought an old boat with a 55 hp, twin cylinder. Idled fine but
wouldn't open up. Rebuilt carbs and discovered that two screws came off
the air box and were sucked into the reed valves on one carb, holding a reed
open. Fixed that and engine ran fine. But next week it was back to
stumbling and killing when throttles were opened up. Due to floods, I just
got a chance to pull the shroud and look around it. I see a hose (vacuum?)
that runs from the front of the engine housing (intake manifold) to the back
of the air box had pulled loose from the air box (or I had forgotten to
attach it firmly). Any idea of the function of this hose and the
ramifications of it not being connected correctly? My shop manual doesn't
refer to it or show it.

Tom.

On Wed, 27 Aug 2008 00:48:02 GMT, "Tom G"
wrote:

Last year I bought an old boat with a 55 hp, twin cylinder. Idled fine but
wouldn't open up. Rebuilt carbs and discovered that two screws came off
the air box and were sucked into the reed valves on one carb, holding a reed
open. Fixed that and engine ran fine. But next week it was back to
stumbling and killing when throttles were opened up. Due to floods, I just
got a chance to pull the shroud and look around it. I see a hose (vacuum?)
that runs from the front of the engine housing (intake manifold) to the back
of the air box had pulled loose from the air box (or I had forgotten to
attach it firmly). Any idea of the function of this hose and the
ramifications of it not being connected correctly? My shop manual doesn't
refer to it or show it.

I don't know what it does either (my guess is it's some kind of
breather/equalization line), but I had a similar engine, did similar
repairs, couldn't find it in the manual so just hooked it up.

One thing I did have a problem with is timing advance which, in
theory, should work off vacuum, but that seemed to clear up also.

Just some food for thought - nothing constructive.

Short Wave Sportfishing wrote:
On Wed, 27 Aug 2008 00:48:02 GMT, "Tom G"
wrote:

Last year I bought an old boat with a 55 hp, twin cylinder. Idled fine but
wouldn't open up. Rebuilt carbs and discovered that two screws came off
the air box and were sucked into the reed valves on one carb, holding a reed
open. Fixed that and engine ran fine. But next week it was back to
stumbling and killing when throttles were opened up. Due to floods, I just
got a chance to pull the shroud and look around it. I see a hose (vacuum?)
that runs from the front of the engine housing (intake manifold) to the back
of the air box had pulled loose from the air box (or I had forgotten to
attach it firmly). Any idea of the function of this hose and the
ramifications of it not being connected correctly? My shop manual doesn't
refer to it or show it.

I don't know what it does either (my guess is it's some kind of
breather/equalization line), but I had a similar engine, did similar
repairs, couldn't find it in the manual so just hooked it up.

One thing I did have a problem with is timing advance which, in
theory, should work off vacuum, but that seemed to clear up also.

Just some food for thought - nothing constructive.
Timing is either electronically controlled or by means of flyweights and
springs under the distributor baseplate on an inboard. On an outboard
there is a timing plate connected to the carb linkage. I'm guessing that
the hose might be operating the fuel pump with crankcase pulsations.

On Wed, 27 Aug 2008 06:29:37 -0400, Jim wrote:

Short Wave Sportfishing wrote:
On Wed, 27 Aug 2008 00:48:02 GMT, "Tom G"
wrote:

Last year I bought an old boat with a 55 hp, twin cylinder. Idled fine but
wouldn't open up. Rebuilt carbs and discovered that two screws came off
the air box and were sucked into the reed valves on one carb, holding a reed
open. Fixed that and engine ran fine. But next week it was back to
stumbling and killing when throttles were opened up. Due to floods, I just
got a chance to pull the shroud and look around it. I see a hose (vacuum?)
that runs from the front of the engine housing (intake manifold) to the back
of the air box had pulled loose from the air box (or I had forgotten to
attach it firmly). Any idea of the function of this hose and the
ramifications of it not being connected correctly? My shop manual doesn't
refer to it or show it.

I don't know what it does either (my guess is it's some kind of
breather/equalization line), but I had a similar engine, did similar
repairs, couldn't find it in the manual so just hooked it up.

One thing I did have a problem with is timing advance which, in
theory, should work off vacuum, but that seemed to clear up also.

Just some food for thought - nothing constructive.

Timing is either electronically controlled or by means of flyweights and
springs under the distributor baseplate on an inboard. On an outboard
there is a timing plate connected to the carb linkage.

Ah - well, I always thought it worked like a tractor. Apparently not.

I WAS WRONG!!!

My day is ruined. Thanks a lot. :)

I'm guessing that the hose might be operating the fuel pump with
crankcase pulsations.

That could be - it's been a while since I've rebuilt an outboard.

"Tom G" wrote in message
news:6v1tk.824$p72.2@trnddc05...
Last year I bought an old boat with a 55 hp, twin cylinder. Idled fine
but wouldn't open up. Rebuilt carbs and discovered that two screws came
off the air box and were sucked into the reed valves on one carb, holding
a reed open. Fixed that and engine ran fine. But next week it was back
to stumbling and killing when throttles were opened up. Due to floods, I
just got a chance to pull the shroud and look around it. I see a hose
(vacuum?) that runs from the front of the engine housing (intake manifold)
to the back of the air box had pulled loose from the air box (or I had
forgotten to attach it firmly). Any idea of the function of this hose and
the ramifications of it not being connected correctly? My shop manual
doesn't refer to it or show it.

Tom.

Similar hose on our jet ski runs a diaphram fuel pump.