I figured I would try some NGK Irridium IX plugs on a couple of my engines. I got the plugs and saw that the cap on the top is missing. I have had plugs in the past where the cap came loose and you had to screw it on, but I haven't seen a plug where it was just threads. Do I just push the boot over the threads or am I missing the screw on cap?

The ones I had came with the screw on cap. You can probably take one off a regular NGK plug.

Here's an article that shows how to shorten them if needed. You need a good diamond cutting disc to do it though. www.modelgasboats.com/Magazine...en_a_Sparkplug/

I ordered some and they came with out the cap. I emailed the people where I bought them and they sent me the caps. They said next time ask for them when I order, there was no charge for them.

Ron

Yeah, I found it strange to not have the caps. The guy I order from is great, so no blame there. Unfortunatly I had to go and buy some NGK plugs from the auto store, remove the caps, and use them....kind of a waste. I had some older plugs that just didn't want to give up the caps without damage. These babies are long, but they sure look high tech. Nice piece of hardware and worth the 8 bucks.

Hopefully they will give a little more pep in my step and a nice smooth transition from low to high as claimed.

Hi,
You know that is one step that I have not taken. Let us know how the irridium plugs work out.

I just wanted to report back on the Irridium plugs after a day of running in two boats. I ran the Irridum NGK IX plugs in a Zenoah 260 PUM-stock (AM Sprint Cat) and a RCMK Evo (AM Thunderbolt). I am not the kind of guy to let my want for results cloud reality but I have to say that I was surprised to get a noticable result in both motors, expecially the RCMK.

I noticed improved throttle response and a "smoother" transition from low to high. I ran a new NGK CMR7H as a comparison on the stock Zenoah. I used the same needle setting (which may have been a factor here) on the 257 Carb. I also used a GPS and got 58.4 mph max with the CMR7H and 59.7 with the Irridium running an ABC 2716 10 degree prop. Just to play fair I took these reading after the engine was warmed up from an initial run. Idle seemed better with the Irridium plugs and less breaking up when coming off throttle to low in the water.

All around, I am really happy with my 16 dollar (8 bucks a piece) investment and the plugs sure stays cleaner than on CMR7H. Only PIA was going to buy 2 NGK plugs ($2.25 a piece) at the auto store to remove the caps and install on the Irridium plugs because they came without them.

I also have had good luck with the IX. I run them in my mono but are too long to fit in my hydro. I was thinking about cutting some down as in the how-to articles.