Re: [OMC-Boats] Spark plug wire order for odd-fire V-6

From: Ethan Brodsky <brodskye@...>
Date: Wed, 19 Jun 2013 11:28:25 -0500 (CDT)

On Sun, 9 Jun 2013, Ethan Brodsky wrote:
> If anybody has an odd-fire V-6, is there any chance you could look at the
> distributor and tell me:
> a. Which port is #1? (relative to the screen and the front of the engine)
> b. Do the ports increase clockwise or counter-clockwise?
> c. What is the part number on your distributor cap?
> d. What order are the cylinders wired to the distributor?

Thank you to Jeff L, Tom K, Will H, Hoggar, and Dave R for their really
helpful responses, both on and off the list. This list has been really
helpful for me over the last decade and I'm glad it is still as great as
always. I will summarize the results below.

With those responses, I was able to figure out that I'd reversed the order
of plug wires 1 and 2, which was causing occasional gentle misfires at idle
and more violent (loud "pop") misfires under load. It also made the rest
of the plug ordering seem really confusing. I'm guessing I either
mislabeled the wires as I removed them a few weeks ago, or possibly messed
them up in the fall when I was working on some other stuff before

To summarize, the plug markings on the distributor cap go counterclockwise,
with terminal #1 being right over the vent screen. The position of this
vent screen is still an open question - on my and on Tom K's boat, it was
about 45 degrees to starboard (front left side if you're looking aft at the
front of the engine), but on Jeff L's boat, it was somewhat to port ("to
the right", if you're looking aft at the front of the engine). I don't
think this matters too much - it's just a matter of preference, as all that
really matters for timing is the relative position of the housing and the
rotor, and that the points are on the "front" where they're accessible
without taking everything apart.

Portside cylinders are 135 (front to rear) and starboard cylinders are 246.
The plugs for each cylinder are attached to the terminals on the
distributor cap in the order marked on the distributor cap - the plug wire
from cylinder 1 goes to labeled terminal 1, cylinder 2 to terminal 2, etc..
up to cylinder 6 going to terminal 6.

The crazy firing order marked on the valve cover (165432) is "implemented"
by having the distributor cap labeled in an appropriate manner for this
engine. If you have the wrong distributor cap (e.g. one for an even-fire
engine), then it is very possible that the terminals will be labeled
clockwise and you'll have to attach the wires according to the firing order
stamped on the valve cover - note that this is an exact reversal from
123456, if you mirror it around #1.

While I had everything apart, I replaced the points/contact assembly
(Sierra 18-5310, includes a capsule of distributor grease), condensor
(Sierra 18-5345), rotor (Sierra 18-5419), and distributor cap (Sierra
18-5388, OMC 383586). With the exception of the distributor cap, all of
these parts are still in current manufacture and available from West
Marine, go2marine, or any Sierra dealer (though better prices can be had on
ebay from one of the many dealers clearing out old stock).

The cap was discontinued by Sierra a couple years ago but is still
available on ebay from a few vendors - be careful with which one you order,
as Sierra chose idiotic part numbers (18-5388 = 383586 for 67-71 155-hp
odd-fire V-6 (discontinued); 18-5387 = 383588 for 63-65 150 hp V-6; 18-5386
= 383587 for 72-76 165 hp I-6), and the first vendor I bought one from sent
the wrong unit.

All in all it cost about $50-60 to replace everything but the coil. I'm
guessing everything was fine other than the points module itself, but I
figured it was going to be a lot of work to disassemble everything and it
seemed silly not to replace it all. In retrospect, I probably should've
just replaced the points - everything else was in fairly good shape and
it's super easy to disassemble and reassemble the distributor.

I considered installing a Pertronix Ignitor module (1165) based on all the
positive reviews on this list, but decided to stick with the existing
electromechanical system because it was cheaper, seems fairly reliable
(this is the first work I've done on it in the ten years I owned the boat),
and because I disliked the fact that first-generation Pertronix units can
be damaged by leaving the key on with the engine not running (fixed in the
Ignitor II, but they never made an odd-fire version).

I confirmed the timing by identifying TDC on cylinder 1 (pulled the spark
plug, dropped in a screwdriver, and rotated the crank pulley by hand); then
pulled the valve cover (good opportunity to replace the old cork gaskets
with modern rubber ones) and made sure that both valves were closed
(showing that I was at the end of the compression stroke and not the the
exhaust stroke). This occured when the distributor rotor was pointed
towards terminal 1, and the points opened at around 10 degrees BTDC, so
it was close to correct.

I then buttoned it all back up and started the engine and rotated the
distributor housing to adjust the timing to 5 degrees BTDC at 1000 rpm
(using a timing light) - then confirmed proper advance at 1800 and 2800 rpm
(as specified in the dealer service manual) to be sure the mechanical
advance mechanism was working correctly. It was previously about 5-8
degrees ahead of where it should've been. It now idles and revs super
smoothly, though I haven't yet had a chance to take it out on the lake and
try it under load.

Thanks everyone for the help!

Ethan Brodsky
Received on Wednesday, 19 June 2013

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