4 cyl merc ????

[vislaguy]

I have seen a few motors with the distributor style ignition and mostly the mag type like I use.whats the plus or minuses to either.??? also I want to balance my pistons where is the best place to remove material on the piston?? thanks mike

[David_L6]

Mike,

I've never run anything other than a mag on a 4 cylinder. Mags are simple. If your motor cranks easily in the water your mag is in pretty good shape... Clean and gap the points, install new wires and condenser and you should be good to go. I run mags straight off of fishing motors without doing anything other than cleaning the points more often than not.

If Dave Scott doesn't see this thread e-mail him. I'm sure he's run both and can answer your questions a lot better than I can.

[crankbearing]

mag vs electronic

Well Mike,

The Mag is as David said "simple" and that is the fact. I would look at electronic from sheer lack of Mercury parts for the mags. Since you are not able to get original parts for the mags any longer you have to use non oem points and the springs and materials used are not the same. The reason the old mags were so reliable is you could get a 38 - 42 Oz. Lbs torque on the points and they would not flutter at 8K and some of the new points may. the other fact is that the center cap and wire plate are now in two the 200$ range and you cannot buy them separate a coil is +100$ etc...

The self contained early distributor is an easy find and they are hard to get parts for as well but do not break nearly as much They are more consant and have a hotter spark output due to the electronics. They tend to be a little harder to setup but once done they are solid all the time.

My only concern with this type of ignition is Merc beefed up the top crank cheek in relation to starting to use the electronic igniton, I was always told that this was to combat breaking the crank due to the stronger ignition, but there could be several reasons for the crank mod. The most obvious is the newstyle Shorter Rods with Big wrist pin pistons all this came about when the new ignition system was introduced.

There are still lots of things you can do to make a magneto work RIGHT all the time. Dwelling your mag is the first key and all new bearings every 2 year is another. Make sure your belt is proper tension and the pulleys are not beat beyond there use.

But to me it's personal choice and if I was using a mag I would buy a brand new FM mag and bolt it on and have one in the trailer for spare and a little hint is you can still dwell them at 54 degrees .

Regards,

[vislaguy]

thanks

hey dave what is a fm mag?? and what is seting the dwell,I'm still learning about the mags and how they work, so far I have had good luck with them but I just picked up another 500 motor and it has a distributor and I thought about trying that setup but really wasnt sure where to start with that. So on a 44 mod motor what would you run??thanks mike

[crankbearing]

cont'd

Hey Mike,

FM is Fairbanks Morse and the reason I mention those is that you CAN buy them as a new unit.. Dwell - Well you set your initial gap on the points at .008 - .012 or whatever this is what most people do and let them go at that.. but dwell is dialing in that gap.. You use a service tool from Merc (dwell plate) and a continuity meter or buzz box (timing device) just does what the name implies.

Dwell is setting the amount of time the points are allowed to be open (rise time) The other thing that gap does on a four cylinder is sets the Rise time of each cylinder pretty much the same. If you had a perfect mag shaft this would not be an issue as every lobe would be perfect and you should get the same rise time per cylinder with just setting the gap. Mercury is 48 degrees and FM is 54 degrees the coil is what allows for more dwell. The Oz. Lbs torque I spoke about is very important at static on the bench dwell is great and you may get it bang on and with a worn mag shaft you may not, the Oz lbs torque keeps it at 48 degrees at higher rpm (flutter) If you can set the Oz. LBS torque to 40 at least you will be good.. There is a secret in this paragraph, there are few guys who will recognize it.

Next point, the cam wick, this is the part opposite the points.. There is a gap setting for that as well, I have seen a lot where the wick is set tight against the mag shaft, this is a no no. I usually set them at .005 - .010 or just a slight gap between it and the shaft. Another things I will do is bend and shape the points to get the faces perfectly aligned.

If you have the other ignition and are not familiar with the mags I would run it. The last thing you want is to be sitting on the beach for your mag not working. You can get parts for that igntion from Rapair (CDI) Electronics

Regards,

[Tim Weber]

Dave,

I know you can get parts for an FM but where do you find a new one? Also, where do you get parts for the Merc mag. I have a couple that need points, condensers for an old 55H?


Tim

[crankbearing]

parts

Hey Tim,

You can buy a new FM last time I checked direct from the manufacturer, Obviously under a different part number but that was a few years ago I checked. As for Merc part, depending on your points, you can buy points etc via Napa and Sierra.. they have a kit for the merc mags. You can still get coils from Mercury as well as center and end cap. We got a new coil last year from Toronto. 80$. I think.

Regards,

[quicksilver96]

Merc 500 Ignition

hey dave what is a fm mag?? and what is seting the dwell,I'm still learning about the mags and how they work, so far I have had good luck with them but I just picked up another 500 motor and it has a distributor and I thought about trying that setup but really wasnt sure where to start with that. So on a 44 mod motor what would you run??thanks mike

I just put together a D Mod engine from a Merc 500 and am using the Stock Ignition (Merc Lightning). Not really shure how it will work but should find out in Franklin Pa. on Memorial Day Weekend. I intend to swing the mag for easier starting and to lighten up on the belt. I know it fired on the first pull after putting the engine together. How it will run when wide open is anyones guess right now. Bob Rusnak N-96