Hi all,

Just recently bought a little runabout with a 1999 15 Johnson. It seems to
feel like its missing at low speeds but runs fine at higher speeds. I'm not
experienced with boat engines, but I am with cars and it sounds / feels like
its trying to fire but not quiet. The plugs (x2) look ok and not fouled.

Any suggestions on where to look first?

Thanks in advance for your help

I find a spray bottle of water is an excellent way to find a nonfiring
cylinder. Run it a low rpm for a few minutes and then spray a little water
on the exhaust as close to each cylinder as you can. If one does not turn
to steam as quickly as the other then you have found the problem cyclinder.
If it has two carbs that would be the first place I look. A lot of carbs
have a low speed circuit. Sometimes two cylinder engines also have
independent ignition too.

"dragonfly" wrote in message
u...
Hi all,

Just recently bought a little runabout with a 1999 15 Johnson. It seems
to feel like its missing at low speeds but runs fine at higher speeds.
I'm not experienced with boat engines, but I am with cars and it sounds /
feels like its trying to fire but not quiet. The plugs (x2) look ok and
not fouled.

Any suggestions on where to look first?

Thanks in advance for your help

I don't think James has seen an outboard with the cover off...You need
to provide us a liitle more info..I'm assuming it's a 2 stroke? What
do you consider low speed?(idling, 1000 rpm..? )...Does it
stall?...Does it happen when cold, hot or all the time? Does it miss
when out of gear, or just when underway? Fill in the details and it
will be easier to suggest a course of action...
markv

On Sat, 21 Jan 2006 21:20:09 +1100, dragonfly wrote:

Hi all,

Just recently bought a little runabout with a 1999 15 Johnson. It seems to
feel like its missing at low speeds but runs fine at higher speeds. I'm not
experienced with boat engines, but I am with cars and it sounds / feels like
its trying to fire but not quiet. The plugs (x2) look ok and not fouled.

Any suggestions on where to look first?

Thanks in advance for your help

Replace the spark plugs. They don't have to look fowled on a two stroke.
If this cures it, buy two more. Just because you'll need them when you
least expect it.

I don't know if this is the same as your problem, but, I just had a similar
problem with my 9.9 Mercury motor. I fought it for 2 seasons then let the
experts fix it.
Turned out it was a water jacket gasket allowing water into the combustion
chamber.
Repair shop charged me around $190 to fix it.
It works like a charm now!

Fredo
"dragonfly" wrote in message
u...
Hi all,

Just recently bought a little runabout with a 1999 15 Johnson. It seems
to feel like its missing at low speeds but runs fine at higher speeds.
I'm not experienced with boat engines, but I am with cars and it sounds /
feels like its trying to fire but not quiet. The plugs (x2) look ok and
not fouled.

Any suggestions on where to look first?

Thanks in advance for your help

Ok here are some more precise details of the motor:

2 stroke 1999 short shaft Johnson 15hp. It doesn't stall, and it doesn't
even seem to run rough at idle. Its hard to explain, it happens when
underway say about 2 knots or so but when you open it up from anywhere from
8-20 knots it runs fine. Happens when the motor is cold or hot (all the
time) - no change. Its not back firing but more like "half" firing if
that's even possible. It only appears to do it when in gear (rev or
forward) but I have not run it too high in the rev range in neutral.

Starts perfectly with one pull so no complaints there.
If you need anymore info plz let me know and I'll explain as much as
possible.

Thanks again for your help so far guys!!

"markvictor" wrote in message
ups.com...
I don't think James has seen an outboard with the cover off...You need
to provide us a liitle more info..I'm assuming it's a 2 stroke? What
do you consider low speed?(idling, 1000 rpm..? )...Does it
stall?...Does it happen when cold, hot or all the time? Does it miss
when out of gear, or just when underway? Fill in the details and it
will be easier to suggest a course of action...
markv

Yeah I think i'll do that to have them as spares, nothing worse than being
in the middle of nowhere and having a broken down plug

"RLM" Here@ home.invalid wrote in message
news:TcAAf.11577$jd5.10609@trnddc02...
On Sat, 21 Jan 2006 21:20:09 +1100, dragonfly wrote:

Hi all,

Just recently bought a little runabout with a 1999 15 Johnson. It seems
to
feel like its missing at low speeds but runs fine at higher speeds. I'm
not
experienced with boat engines, but I am with cars and it sounds / feels
like
its trying to fire but not quiet. The plugs (x2) look ok and not fouled.

Any suggestions on where to look first?

Thanks in advance for your help

Replace the spark plugs. They don't have to look fowled on a two stroke.
If this cures it, buy two more. Just because you'll need them when you
least expect it.

Any Ideas guys?


"markvictor" wrote in message
ups.com...
I don't think James has seen an outboard with the cover off...You need
to provide us a liitle more info..I'm assuming it's a 2 stroke? What
do you consider low speed?(idling, 1000 rpm..? )...Does it
stall?...Does it happen when cold, hot or all the time? Does it miss
when out of gear, or just when underway? Fill in the details and it
will be easier to suggest a course of action...
markv