On 5/22/2013 5:20 PM, Eisboch wrote:


"Hank©" wrote in message
eb.com...

On 5/22/2013 10:10 AM, Eisboch wrote:


"John H" wrote in message
...

On Tue, 21 May 2013 20:41:39 -0400, Wayne B
wrote:

On Tue, 21 May 2013 02:55:41 -0400, "Eisboch" wrote:



"Rupp0003" wrote in message ...


1989 merc 3.0 starts fine, runs fine for about half an hour at any
speed
or rpm then starts to miss and will eventually stall. Fuel dripping
from
flame arrestor but only once rough running starts. Will sometimes
restart after a few minutes and run ok other times will continue to
run
rough and stall.

Are there any members out there that might have some insight into what
the problem might be?

--------------------------------------------------------------------


Bad coil. (Goes bad when warm .... ok when cold.)

====

Probably right. I had that problem on one of my old 454s. To make
it worse, some genius decided that the coil should be mounted very
near the exhaust manifold.


The dummies who built my old Proline put the live well right above the
coil, with no sealant. Took
me two coils to figure out where the problem was.

I think Eisboch nailed it. At the price of coils, it's well worth giving
a replacement a try.

John H.

----------------------------------------

Maybe. Educated guess due to similar experience. The fact that the OP
says it runs fine at any speed for about half an hour makes me think
it's probably not carburetor related. Sounds more like something heats
up and fails which is more likely an ignition problem and the coil
(especially if it's older) is suspect.

Had the same thing happen one morning on the old '82 Century. Mrs.E.
and I were taking a ride up to Boston Harbor from Scituate. It was
probably just about in the same timeframe that the engine sputtered and
died, right in the path of one of the Boston to Provincetown high speed
boats that was just getting up on it's hydrofoils. It blew by us in a
rush with it's horn blaring. After sitting dead in the water for a
while the coil cooled off enough to restart the engine and we limped our
way slowly back to Scituate at idle speed.


I wouldn't put money on any of the suggested diagnosis, including mine,
but it would be worth checking out all of them. Most of the coil
overheating problems show visual signs like bulging or oil under the
high tension lead. Carrying a spare would be good insurance.

----------------------------------------

You're right of course but the OP's description of how the engine was
acting sound VERY familiar. I was having the symptoms for a week or
two (ran ok cold, started getting rough when warmed up and was very
evident when I tried to push that tank of a boat up on a plane after
being warmed up. I think you were still around here after the Boston
Harbor experience. When it died that time, it blew the high tension
wire right out of it's seat and indeed, there was oil on the coil. But,
after it cooled down for a while, it worked enough to putt-putt back to
Scituate. New coil fixed *that* problem and we moved onto the next one.
That boat should have been retired from service years before. :-)

He had a symptom that you didn't have.

Ask Harry if he went to the Navy Seal museum just down the street from
the Disney resort he stayed at. They had some pretty interesting old
boats on display.