220 GPU (PE-150) Spark Plugs

[Anonymous]

Hey All:

Does anyone have any recommendations on what spark plugs to use in a 220 GPU (PE-150) engine? I've been using Champion D16s, but they seem to foul prematurely, and D21s, but they cause pre-ignition. I thought I had hit the right plug when I went to Autolite ??? (I can't remember the number), but they fouled after about 6 hours.

My setup is:

PE-150, made in '59, overhauled in '79, approx 200 hours since O/H
Original Zenith carb
Original Bendix magneto w/Hi-performance solid-core ignition cable
70x28 wide-blade wooden prop (F-Prop)
12x7 (Laser-like) fiberglass hull

Boat runs strong (like up the hill, down the levee, through the dirt parking lot strong), and we get about 46.5 mph (GPS speed) @ 2750 rpm, but it's becoming a nuisance having to change the plugs every third or fourth trip.

Or maybe I should just invest in a spark plug cleaner?

Thanks

Doc

 

[Anonymous]

I ran Denso L 14 U in mine. No problems. Available at our local NAPA parts store.

 

[Anonymous]

I am running NGK AB6's in my dual plug g.p.u. with over 185 psi compression. I have found the best gaps are .015 on the bottoms and .018 on the tops with no fouling issues. Running larger plug gaps seem to make this engine run rougher at idle speed.

Larry

 

[Anonymous]

The Continental GPU 220 and most aircraft motors utilize a magneto ignition. They’re extremely reliable but their only down fall is they generate their own spark energy via the magneto. This type of ignition generates a very week spark at lower engine RPM’S however the spark does get stronger as engine RPM’S increase. That’s why you must run such a tight plug gap, especially at idle. If you run a large gap the mag doesn’t generate enough spark energy to properly cross a large gap at idle. The reason sprint cars and top fuel motors can run magneto’s is because they operate around 9,000 RPM and they develop a huge amount of spark energy at these high RPM’S. They create so much voltage the spark will actually burn the spark plugs tip’s off. Not to mention sterilize you for life if you get shocked by it. Most automotive ignitions especially MSD, Mallory and Crane generate a consistent voltage across the plug gap thru out the engines RPM range. I modified a slant six Dodge distributor to fit on my old 220 GPU and utilized a Crane HI-6 ignition. With this ignition system I gapped the plugs @ .045. This motor started up immediately and idled much smoother. What was most interesting I ran the same timing and didn’t change anything else on my motor and it picked up around 200 RPM’s at Idle. Just as the other guy mentioned I would tighten up your spark gap and try running a .016 gap. If that doesn't work try a .014 gap if you still have problems you may have a weak ignition that needs repaired. With a smaller plug gap you should notice a difference in how easily your motor starts up. I recommend the NGK’s or Autolights. I hope this helps you.

 

[Anonymous]

what should the gap be on my 540, would it be the same as a gpu?

 

[Anonymous]

Thanks for the information, especially waterthunder, who's explanation of magneto theory answered a lot of questions I had wondered about over the last year or so.

One of the main problems we had with the boat after we put in the "new" GPU was that, after a few hours, the engine would go into a "hard start" mode. The first time it happened, we spent the night in the 'Glades (on the boat) after wasting the battery trying to start the engine. We finally figured out that changing the plugs always seemed to fix the problem (fresh plugs). This caused a lot of SWAGs on things like fuel mixture, Zenith vs. Holley, timing, you name it, we f'd with it. Oh, BTW, the gaps we always used were .026.

Last night, I took the Autolite plugs (they're AutoLite 386) that had seemingly fouled and were beginning to demonstrate the "hard start" problem, changed the gap to .018 (I was kind of concerned about going to .015 right off the bat....I don't know what effects a smaller gap will have on head temp, pre-ignition, etc.), put the plugs in, and started the boat right up. Two cranks, no choke kind of start. It did seem to be running rough, but I think maybe one of the plugs is fouled (I'll clean them up as soon as I can get some beads for my cleaner, which I did get yesterday). But changing the gap certainly seemed to resolve the 'hard start" issue, as demonstrated on at least 6 occasions last night (the engine always started on the 2nd or 3rd crank).

Something else.....there's nothing like screamin' through the tall grass at night, under the lunar eclipse, without lights.......'specially with two first-timers on the boat!!!! What a blast!!!

Again, thanks a lot for all your replies.

Doc (from South Florida, usually in WCA-2A)

 

[Anonymous]

woody
Guest





Posted: Wed Oct 27, 2004 3:52 pm Post subject: gap on an 0540

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what should the gap be on my 540, would it be the same as a gpu?

If your ignition is up to snuff you should run a plug gap of .025 if your ignition is week or you burn allot of oil or if your plugs are getting fuel fouled because your motor is long in the teeth running a tighter plug gap will help. Your motor will perform the best running the largest plug gap your ignition can handle. The longer the duration of the spark the more efficient your fuel combustion will be.