40/44 tech and buy sell swap

[mtechmarine]

Spray shield

Steve -- will this spray shield work with a Merc SS ignition distributor?

"Cuz I am sure I'll need one!

[trident]

Spray Shield

Mike, That Lou Witham design that Steve is selling would be an excellent choice, if you are not using a tail cowl on the boat… then again it might be great with a tail cowl, too.

Sometimes its way smarter to buy a quality part than to spend too much time making your own… my 2 cents.

Jerry

[Guest]

Magneto

There is a lot of discussion about what ignition is best for a MOD race engine. My engines all have magnetos with the later Mercury KD series being the most desireable. Over time I have found that the magneto setup is quite trouble free and in racing applications can run at 10,000 RPM.

A friend sent me a mag to check for him before the racing season. It was a Mercury KD-2 with an older cap that was chiped and not the desireable configuration. The first thing that I do is run the mag on my test stand to see where the mag will not produce spark on a consistant basis. This unit started to fail at about 6,600 RPM and at 7,800 RPM most likely would not run an engine. The sparkplugs in my test setup have the ground electrode removed so the gap is about .2 inches. The series of photos shows the basic process. One thing quite inportant is to follow section IV in Mercury manual C-90-25500. Additionally a couple Mercury tools are needed.

After the test run I will disassemble the mag to determine the condition of the of the cap, rotor and base. In this case I discarded the cap due to parts cracked off where the wires go in. This being an older cap without the O ring seal on the wires would have caused problems if it got wet. After cleaning all the parts with CRC Electro-Clean and then checking for carbon tracking or cracks I set them aside for assembly later. Of note try to keep from getting finger prints on the parts after cleaning in that the salt can cause an issue at a later time.

The inside of the mag was in very good condition with no major issues. In order to determine why the mag had a hard time producing spark at high RPM there is really only two things that cause a problem. They are point spring tension and point gap. In this mag the gap was found to be .005 inches where a used set of points Mercury defines .008 inches as desireable. When inspecting the magneto point cam make sure the running area is smoth and without groves. A worn cam can cause excessive point wear and the relating loss of clearance (gap). Looking closely at the points they were an after market brand with a relatively thin spring. Using 91-29406 spring tension scale I found that the points only had 20 oz. tension where the desireable is 33 to 37 oz. With new poing I look for the high side and set the points at 37 oz. These two issues caused the points to opeate poorly at high RPM. After checking the coil and condenser using the Magneto Analyzer and finding them acceptable the mag was ready to reassemble.

I like to use the Mercury factory 393-1504 point kit when redoing the magneto. They have all the small parts along with a new cam lube wick which helps slow down point wear. I like to set a new set of points at a tight.010 inches (high side of Mercury recomendation) which allows them to wear and still be at the correct dwell and gap after about 5 hours running. Once the new points were installed a check of the tension showed them to be at 37 oz which is the high side of the desireable range. This is a good place to be for a mag used in a racing application. The new cam wick was installed to provide lubrication and we now have a completed mechanical side of the magneto. After mechanical assembly a dwell check was accomplished to make sure we were close to what was required after the points have been run for a bit they should be at the required setting. Setting the points to the high side of the allowable gap band will cause the dwell to be off a bit but this is not an issue in that the dwell should be set after about 5 hours of running.

During the initial run the wires were found to be in good condition so they were reused. Removing them from the old cap and installing them in a new cap I like to use CRC technician grade electrical assembly lubrication on the wires to help keep moisture out of the Cap/wires. Now we are ready to strart the last assembly process. Install the cover and put the screws in loosly. Next use tool C-91-26351 installed on the rotor shaft and place the cap on the cover. Now tighten the 4 screws on the cover and then remove the cap and tool. Using this proces we assure ourselves of having uniform clearance between the rotor and cap contacts. Next we are ready to install the rotor. Make sure the tension spring is still in the rotor splines and then press it on the shaft. Use a paper towel to hold the rotor to keep from leaving fingerprints on it. Now install the cap and we have a completed magneto ready to be test run.

After installing the mag on the test stand I do some checks. The first is to see when we start getting good spark with the large gap plugs. This mag produced spark at about 1,600 RPM. The next check is to bring the unit up in RPM slowly until I get to about 10,000 RPM which is the limit of the test unit. This mag produced great spark at the level. After this check I run the mag at about 7,000 RPM for 15 min. to make sure there are no heat issues. The last thing I do is again check the high and low RPM and if all is well we have have a very servicable ignition system

I like using a magneto in that is very easy to find good ones, parts are still available and you don't have to worry about a power source. I understand that everyone has their own ideas about ignition systems but this is by far the least expensive way to go when your starting out.

Hope this helps,
Alan

[Guest]

Magneto

Here are the last two photos. Note the spark produced at 10,000 RPM. This spark pattern was produced by this mag from about 2,000 RPM and up.

Alan

[sam]

I'd add a pressure box to your set up. Nothing confirms voltage output like pressure; it helps you find a bad coil that could elude you with the rest of your set up.

[Guest]

Magneto testing

Hi Sam,
I will see if I can work up a box that will be safe when pressurized and I can still view the spark. I agree that you have a harder time firing a plug when under pressure and it would be a good improvement. By using the extra large plug gap I tried to compensate for the lack of testing under pressure.

Alan

[Larry M]

I'd add a pressure box to your set up. Nothing confirms voltage output like pressure; it helps you find a bad coil that could elude you with the rest of your set up.

I was going to say the same thing about plugs under pressure. I have a mag tester also and I put the plugs under pressure and it makes a difference on how they fire. A mag set up like Alan is doing will work fine. I went to a CD ignition a few years back and I have stayed with it. The battery is the only drawback I can see. I have tested it with a meter and it will put out more voltage than the mags I have tested if than means anything.

Larry Mac

[PRO-MOTIONRACING]

That's the way to do it. For a quick budget way to check mags/ points while the cap is still off I use a bent coil tang (or what ever that thing is called) pointed toward ground with about a one inch gap. First I spin it by hand (easy starting) then I use a pneumatic angle grinder with a countersink bit and a three inch section of rubber hose as a coupler to spin the mag up. For extra fun let it slip a little in your hand, the results can be shocking !

[blueskyracer]

Allan those are great pictures and info for us rookies. Thanks again

[John C167]

Dale;

Always wondered where you got the "curly hair" from !

Mike;

Get the boat"wet" yet ??????? We had great weather this weekend, good time to test (Of course, I was working ! )!

John B.

[EKorpe]

Ign

TWO letter's CD

[blueskyracer]

Dale;

Always wondered where you got the "curly hair" from !

Mike;

Get the boat"wet" yet ??????? We had great weather this weekend, good time to test (Of course, I was working ! )!

John B.

We are taking the boat off the jig tomorrow and hope to see if the motor has a little pop in her. We could not test this weekend since they drained the reservoir and the weather sucked. Snowed and blew all weekend. Sucks!!

[John C167]

Mike;

Snow, OUCH ! Guess spring is not there yet !

John B.

[blueskyracer]

Mike;

Snow, OUCH ! Guess spring is not there yet !

John B.

We are beginning to think Spring is not coming so we are hoping for Summer!

[blueskyracer]

This is a contest to see which historian knows whos spray shield I will be using on my new D mod.

I must say that our web site has been a great source for parts and assistance in getting ready for this class. We are now ready for the first race Memorial Day weekend.