Ignition

[fat rat]

Anyone here running a Merc ignition with there shop built blower motor (non-Merc 600sc, 800sc or 900sc). trying to figure out the pros and cons between MSD and Merc. I've ran MSD in the past never had a problem, never had a Merc....been running jet boats for years. Thanks for any input.

[ODDD1]

as soon as you start squeezin the air/fuel that hard a stock ignition will show up weak....MSD will crutch alot of problems...definately the way to go....

[superdave013]

Gotta agree with ODDD1. MSD is so sweet. I used to run a super mag 3 but I am now an MSD convert and loving it.

[GotTheFever]

Correct me if I'm wrong, but I think the stock Merc ignition with a high output coil will be more than adequate for most marine applications. Here is my reasoning:
The only responsibility of an ignition system is to deliver a spark, which ignites the air/fuel in the cylinder. There are two elements of this spark that are crucial, timing and intensity.
The Merc ignition is a pointless system where the timing of the spark is controlled by the interruption of a field coil. Older ignition systems that used points could not keep up with this demand when the rpm got too high, therefore the dual point and magneto systems were used. The pointless systems, however, have no problem providing an accurate spark for the range that most marine engines max out in (5,000 – 6,000).
The intensity of the spark is dictated by the coil. A coil produces a spark when the energy flowing through it is stopped. There are two factors that dictate the intensity of the spark. The first is the amount of current going through the coil. This would be 12 volts, which cannot be changed. Older systems used a resistor wire between the points and the coil. This would keep the points from burning up, and reduced the output of the coil. The stock Merc ignition system does not use such a wire. The second factor is the number of winds within the coil. High output coils contain more winds than stock coils. You can purchase after market coils that are able to put out 50,000 volts, using the stock Merc ignition system. This is twice what the stock coil puts out and is more than enough for most supercharged engines. I found it impossible to kill an engine when fogging the cylinders on engines with high output coils.
MSD systems are great for high rpm, high compression systems, like those used on dragsters. For you marine application, try a high output coil. It’s a lot less expensive and easier to install.

[ponponracing]

Merc and MSD ignition are both excellent choices with blower application. From my experience, MSD give you the advantage of multiple sparks when you turn low rpm with no boost and low static compression ratio
from a blower prepared motor. But the best thing of this system is that you can use their timing retard devices (according to rpm or manifold boost pressure) to lower the ignition timing when you are on boost. Remember that boost means less timing. More you boost, less timing you should have. If you put a total timing of 24-30 timing with any regular ignition system, your initial timing will be too low and in the non boost situation, when you need good timing to burn the poorly compressed air/fuel mixture, you will throw away unburned gas. Meaning pollution and gas money from your wallet.

[formula93]

Jacobs ignition.....keeps the stock mercruiser distributor (for no corrosion- msd has problems with that!!)) see offshoreonly.com and search for MSD ignition....many problems there !.
The Jacobs has a multiple spark, extremely high voltage, variable pulse width, etc.....
added 300 rpm on my blown 93 formula. Gotta have it !!

[ponponracing]

You are right formula about corrosion on MSD. But you have to keep an eye on Merc harness and connection. Their electronic box can also give you problems. What I did with a lot of succes is using the stock Merc system amplified with a MSD 7ML box. Their timing retard ia also excellent or even better if you hook it right.
Thanks for the info on Jacob. I'll sure visit their site.

[fat rat]

Out with Merc in with a MSD 6M-2 and there marine distributor. I got a small fortune in this motor, no time to skimp. When you guys talk corrision, are you talking about there pro billet dist. and 6A-L ignition or there marine ignition discribed above? Thanks for any reply in advance.

[ponponracing]

Rat,
the corrosion I could see with MSD is under the cap. After a boating season (I'm living in Canada where boating last one season, period), I opened a ditr. cap to discover that the trigger was completly covered with rust, and the boat was used strickly in soft water. Even the counterweight were rusted, the advanced springs and the curve bushings were the same. The solution was to spray the inside with WD-40 once in a while and to blow it with care not to be flooded.
You also have to be carefull were you install the box: if it get wet, it will be
junk. Install it away of electromagnetic field, or you may see misfiring. Use the marine version since it's better insulated against moisture, as they claim. If you have a blower, use their timing retard box:it works really good.
The distributors I sold were part 8454, some are still running good after 7 years, with maintenance.
Keep in mind that any ignition system need maintenance in an hi-perf. engine.
By the way, the Merc spark plugs wires are the best I could use in a boat up to know. They are moisture proof and they give good spark.