Which Spark Plug? 1985 2001 Ski Nautique

Sort of like that yes. On lake as I type. Again WOT it flies but moving slow at idle or even 3000 RPMs has a shutter about kind of shakes a little bit

The shudder is at idle as your moving thru the no wake zones. WOT is no problem at least doesn’t feel like it. Boats flys at full throttle. Shutter is also present even if you push the throttle up a little but over the idle speed.

Thx guys. .040 is what we went with. Unfortunately it didn’t really fix very slight shudder at idle. Any ideas?

merbesfield wrote: I left the gap at .40. We will see.

A .40 gap is kinda beyond huge, a .040 gap on the other hand sound a lot better

Autolite 24 plugs at .040 inch gap with your Pertronix will be OK.

Points used .035 inch plug gap through the years and it would work just fine with your Pertronix also.

Pertronix generally says you can open your gap about .005 to .007 with their ignition setup.

Frankie, there is nothing wrong with using ngk plugs on a 351w.   If you want to use autolites, go ahead, but ngk and other plugs will work just fine.

You speak the truth:
1998 Engine 4 Options

The more I look into this, the more complicated it gets. My owners manual shows I need an Autolite 303, not the 24 everyone is saying I need, and the Autolite 303 is still a good number; my parts house has it in stock. Now, check this out...when he looked up my engine in his book, he showed it calling for an Autolite 23. GEEZ. I have now left a message with PCM in Little Mountain, SC, complete with my engine serial number. I'm going with the plug they say I should use. Just as a reminder to anyone reading this, I have a '98 Ski Nautique, with the 351 Ford carburated engine, 260 hp. According to my manual, there were 4 engines available that year: one Chevrolet 320 APEX, one Ford GT-40 with 310 hp, and two carburated engines, the 260 hp that I have, which they called "standard," and the 285 hp they called "high output." Both of the carburated engines are Ford. At least I'm learning something. Another thing I have learned is that I need to appy anti-seize lubricant to the threads of the spark plugs.

It is the 260hp engine. I had no idea about the threads, and this may explain why a couple of the plugs took downright force to remove. So the threads are a different depth, and that's it?

Quick question for you. I have what you call "standard heads," since I have a carburated 351 Ford engine in my 1998 Ski Nautique closed bow. I went to change the plugs for only the 2nd time in 1200-1300 hours, so the set I'm changing probably has 600 or so hours on them. Even though apparently my engine calls for the Autolite 24's, when I took out one of the old plugs to go buy new ones, I realized I had the 764's. I either made a mistake when I changed them out the first time, or someone told me to use the 764's, or that it didn't really matter, or whatever, certainly can't remember. Here's the thing, these things look excellent, even though apparently they are the "wrong" plug for my boat. I don't know enough about them to know the difference, but I'd like to hear the opinions of those who do. Could it be that the 764's are OK for both engines, but the 24's are only OK for the "standard heads?" Or is the answer that the 764's worked fine in my engine, but the 24's would work even better? I'd like to know, because I'm tempted to stay with the 764's unless someone can give me a good reason to go back to the 24's (I suppose there's a chance Correct Craft put the "wrong" plugs in to start with, and I just replaced them with what was in there). Thanks for any input in terms I can understand.

Change them out. NGK's are great for jet ski's, etc., but nothing works better than Autolites in those Ford engines. I have 1300 hours on mine, and the Autolites look like new.

Can someone tell me the proper gap for the 24's?

I just had a tune up and the tech used autolite 24's.

I was told by a guy that knows these boats very well, never to run an NGK plug in a Ford motor. I have an 87 with 351.

My 1986 2001 has NGKBPR6FS plugs installed by PO. Are these correct for a 351?