High Speed Miss

"Not a good year for me....con

"Not a good year for me....constantly fixing things. Engine seems to run good up to 25 mph.....after that, if you go to WOT it starts missing on one cylinder (or so it sounds)
Plugs are not that old, Alt. and Voltage Reg are good. Wires, points, cap, and rotor are new. Carb was torn down 1 year ago. Idles smooth, but surges while trolling @ 2.5 mph.
When punched, it goes....but at WOT for any period over about 50 seconds, it starts to miss.
Could the Coil be breaking down under load? It's the only thing I havent replaced. Can they be tested?
I thought I'd try a Coil from the Junkyard.... A cheap way to find out?????
All comments or ideas welcome.

S."

What do the plugs look like?

What do the plugs look like?
It might not be ignition failing at might be a valve problem.

"vacuum test, compression test

"vacuum test, compression test, on a warm motor.Give this a read.

http://www.secondchancegarage.com/public/186.cfm"

"I'd support your thoughts

"I'd support your thoughts about the coil. That is exactly how they act when they go.
If your coil is original, it's at least 16 years old (how long OMC has been history), so time for new anyways."

"The Coil is my last thing...

"The Coil is my last thing... Another friend thought that too much advance could cause this. The Bible says 5 degrees advance. I have yet to put my light on it. Thanks for the input . 33 MPH, as is. I think it has more. I also ran into an old timer who tells me the tach wire should be on the NEGATIVE ( Distributor ) side of the coil.
Its also surging at idle when trolling...could be a carb thing?"

"Well, I checked the timing to

"Well, I checked the timing today.... 10 degrees TOO MUCH. Set it back to +5 degrees.Changed the Plugs. One plug had yet another tiny chunk of molten something shorting out the electrode. Took the boat out, it responds well now.NO HIGH SPEED MISS!!!! After an 8 mile trip down the Lake to the next Port to visit buddy working on his 30 foot Roamer, I get in the channel and it dies.
The Boat has one of those Glass Bowl type filters in the back. Took it apart, no blockage. Put it back together and set out for home. The Boat ran fine down the Lake, but died AGAIN when we hit the Harbour, and went to idle. Strange to say the least.
The next step I guess, is to pull the tank, and clean it out. It'll be a big job, being a 32 gallon galvanized tank.I AM puzzled, and about ready to pack it in for the year!

Scott"

'One plug had yet another

'One plug had yet another tiny chunk of molten something shorting out the electrode.'

Do a compression test. This might look like a mushroom valve.

"[b]I also ran into an old tim

"I also ran into an old timer who tells me the tach wire should be on the NEGATIVE ( Distributor ) side of the coil.


Hmmmm....does that mean that most of us on this board that knew that are old timer's???


By the way Scott....when you say old timer...what kind of age range are you talking?"

"Bob
You should not age your

"Bob
You should not age yourself like that. You are as old as you feel. "

I do not like the word 'ol

I do not like the word 'oldtimer'.
Prefer the VSOP Mechanic!

"OK Morten...I give up, what d

"OK Morten...I give up, what does VSOP (Very Special ??? Person)??"

Bob: when I said "Old-Time

Bob: when I said "Old-Timer" I was referring to my friends wifes Father...who is 76.

""oldtimer" - Of Littl

""oldtimer" - Of Little Disgrace, Trusted In Most External Resourses
"VSOP" I have absolutely no idea "

"For some reason my answer to

"For some reason my answer to the VSOP disappeared, but I try again.
Wiki:
Grades
Martell VS (Very Special) cognac.

The official quality grades of cognac are, according to the BNIC (Bureau National Interprofessionnel du Cognac):

* VS Very Special, or ??? (three stars) where the youngest brandy is stored at least two years in cask.
* VSOP Very Special (less commonly 'Superior') Old Pale, where the youngest brandy is stored at least four years in cask, but the average wood age is much older.
* XO Extra Old, where the youngest brandy is stored at least six, but average upwards of 20 years.

In addition can be mentioned:

* Napoleon Although the BNIC states this grade is equal to XO in terms of minimum age, it is generally marketed in-between VSOP and XO in the product range offered by the producers.
* Extra A minimum of 6 years of age, this grade is usually older than a Napoleon or an XO.
* Vieux Is another grade between the official grades of VSOP and XO.
* Vieille Réserve Is like the Hors d´Age a grade beyond XO.
* Hors d'âge The BNIC states that also this grade is equal to XO, but in practice the term is used by producers to market a high quality product beyond the official age scale. Hence the name "Hors d'age" (beyond age).

But perhaps 'we' go more into the XO grade?"