Sputtering/Backfiring Under Load

Ok, minor change of plans. I stopped by the local CC dealer (Century Marine) and they had a electronic conversion in stock so I picked one up.

At first they wanted to sell me a Mallory one, but then the head mechanic came out said he had a PCM one (part no RP173072) so I got that one.    This mechanic admitted that he thought it was a better one--and I think he told me it was made by Pertronix.

I asked about the coil issue, and the guy said he generally recommends getting a new coil and bypassing the ballast resistor, if for no other reason than it eliminates another failure point.

So I also picked up a new coil from them. The coil is a mallory 9-29703.

I think I will try and install it tonight, see if we can make some progress.   

Jared

Jason: I don't know if my conversion kit is a new version, or an old one, but I hope it is a new one. I now suspect that the problem may have been burned out points due to leaving the ignition on while not running.

Also, do you remember the details of how you were to check the circuit? I have a DVM. Maybe I will try and find Pertronix's phone number and ask them.

sjpitts wrote: I now suspect that the problem may have been burned out points due to leaving the ignition on while not running.

Why are you leaving the ignition on when not running? If you are doing that, you will have the ignition system energized and that will definitely ruin points in a hurry. I assume that you probably have a stereo or something else that was added and you want it to be on while the engine is not running. If that's the case, you better get a new ignition switch that has an accessory position on it and rewire whatever you're trying to run thru that accessory position so you're not energizing the ignition.

So I couldn't find a prestolite 5-69, but I found the sierra equivalant (18-5433) and the NAPA equivalent (IC12). But one issue --- both coils say right on the coil "Use with external resitor" (and the number 903) but the instructions with the electronic conversion kit specifically say to bypass the external resistor.

But I am going to assume that this is still right. For some reason Pertronix recommends a Prestolite 5-69, which would normally be used with an external resistor-- but when used with kit you still bypass. Regardless of what it says on the coil.

Which probably means there is really not the much difference between the 5-69 and the normal points distributor that I already have (the 1223 from SkiDim). In fact, when I measure the resistance on that coil I get 1.7 ohms, which I think is only slightly greater than the 1.5 that would be on the 5-69.

Jared   

/needs to get a life

Well I got the conversion installed---and it runs.

I only had two problems. The first is that when I pulled off the old cam assembly there was a bushing that came off with it--- and then dropped so I wasn't sure which way the bushing went on. I think I figured it out-- the bushing went on so the cam assembly would ride within it.

But then when I got it all installed there was vertical play in the cam assembly. See the picture. The arrow points the cam assembly. I can move that cam assembly up and down about 1/16 of the inch (even with the clip any everthing attached). I am not sure if that is normal, or if I did something wrong.

Anybody know???????

At first I was a little worried that I put the bushing on wrong and this is letting the cam assembly drop too far down, but now I am not sure.

The second issue was that I tried to install the wiring grommet upside down and the wiring was a little short. In the picture it is upside down. When I finally got it installed right the wiring was still tight, but at least it fit.

I removed the ballast resistor, and connected the two wires directly together, effectively bypassing the resistor per the instructions. Left the stock coil in there.

I did not install the new advance springs. The instructions said not to do it unless they were broken or worn. They looked ok, so I left them in. I don't know if I will regret this.

It started right up and ran. At first it wasn't idling to great and I was annoyed, but when it warmed up and I adjusted the timing it seemed to run nice and smooth.

Next job-- plugs, wires and lake test.

Jared

Jason: I am going to call Pertronix tomorrow and get the full story on the coil.

Jason-- mine doesn't look like yours? Is yours a PCM? Mine is came in a PCM wrapper with part number RP173072 on it. It looks just like the one SkiDim sells.

I thought that the PCM was made by Pertronix, but maybe it isn't.

Anybody know?

Jared

Mine looks like that, all it has on the top side is "086" in a rusty brown colored stamp. I have no idea who makes it, and I believe it is wired using the ballast resistor. It will be coming out soon to inspect the advance springs and base plate, as I'm only seeing ~20 max advance @ 3k rpm.

10 base, 20 is what i see at 3k rpm. A little low, but I've already eliminated out fuel and compression. MSD Blaster II which I believe to be oil filled. Shorting out the ballast and the engine will not run.

I should probably go ahead and order this coil. Supposing I do have the PCM/Prestolite EI kit I will be bypassing the ballast then?

Hollywood you need to get yourself a whole bunch more advance and but quick, it will be a whole different boat.

Thats about 5-6 degrees shy.

Ok, I have I have some done some searching, and reread this thread. I am getting that the total timing at 3k RPM for the prestolite with the screw on cap should 35 degrees (10 base + 25 advance), and that it is ok to measure that with the fake a lake as long as you don't keep it at those RPMs for too long.

Is that right?

I have never run my boat that fast on the fake a lake. Or even just in neutral on the lake.

How much should it be at 2k?

Jared

"But when I tried to wakeboard, my wife said it was sputtering all the time. OTOH, the boat could pull my ten year old all day without sputtering. So it appears to be load dependent. "

you could tell your wife she needs to go on a diet.

but the safe thing might be to check the coil if you are still using the old one. A bad coil will produce a weak spark under load.

gigem75 wrote: "But when I tried to wakeboard, my wife said it was sputtering all the time. OTOH, the boat could pull my ten year old all day without sputtering. So it appears to be load dependent. " you could tell your wife she needs to go on a diet. but the safe thing might be to check the coil if you are still using the old one. A bad coil will produce a weak spark under load.

Just to be clear, it was me that was wakeboarding and causing the sputtering problem. If anyone needs a diet, I do.

I still havent replaced the coil, but it is on my list.

Jared

now that you have electronic ignition you don't need to worry about the dwell that is only for points.

Also you need to take the conversin kit out and look at the mechanical advance for broken or missing springs as that is where your issue is. once you figure out what's wrong with the mechanical advance and fix it then reset the timing re-adjust the carb and it should run fine.

sjpitts wrote: The fastest I run the boat is 35 MPH at about 3k RPM. I say this because I am probably missing top end

If that speed is accurate you're not missing any top end at all!

TRBenj wrote: So youre only getting 10 degrees of advance at 3k (10 base + 10 advance = 20 total)? Thats way off- you should see double that (30+ degrees total advance). That might explain your top end issues.

IIRC the balancer cover didn't even have marks past 25.

TRBenj wrote: My EI had the resistor bypassed, and that is consistent with SkiDIM's website. I believe the purple/black wires are the clue that its the Prestolite kit.

I think it's a Prestolite. Purple/black indeed.

TRBenj wrote: The epoxy-filled unit is a good thought, but Id give SkiDIM a call and see what they recommend. I originally had the the conversion module installed and they seemed to think my MSD Blaster II coil caused its early demise. SkiDIM sells a coil that might extend the module's life.

I talked to Vince just a little while ago. He said the ballast resistor is probably the only thing saving the EI conversion kit from the Blaster II coil that's in there.

TRBenj wrote: If youre not 100% certain that the coil is your culprit, get one locally for troubleshooting so you can return it.

I don't think it's the coil causing the problems, but it's not right so I will change it out for the one that doesn't need the ballast resistor from skidim.

Unfortunately the springs aren't readily available. I will bring them to the speed shop I use and see what is available.

For reference, he threw out a few other ideas that might be causing this lacking high end performance:
-retarded timing
-air gap too high, should be ~6 thou instead of the 8-10 called for
-too much oil. 5 qts is enough
-exhaust restriction