When to change out Spark Plugs?

(stevev210) · (stevev210) **Join Date: Feb 2005** 11-23-2006, 11:21 AM

How many hours are you running on your plugs? I know they say to change them at 300hrs for routine maintenance.

(norcalmalibu) · (norcalmalibu) **Join Date: Jun 2004** 11-23-2006, 12:01 PM

It all depends on what motor your running and what type of plugs either copper or platinum?

(tommyg) · (tommyg) **Join Date: Apr 2002** 11-23-2006, 12:11 PM

I (incorrectly obviously) assumed that changing plugs was done as part of the 100 hour service. Took my boat out one day this past summer and was getting some serious vibration for about 2 seconds when initiating some hard acceleration (then immediately totally smooth). Took it in and it turned out I had bad plugs. I think I had about 330 hours on the boat at the time, so 300 hours sounds about right...

(stevev210) · (stevev210) **Join Date: Feb 2005** 11-23-2006, 12:22 PM

Im running a Merc 350 MPI Tow Sport with the AC Platinum Plugs. Ive got 325hrs on the boat and havent had any problems but for Routine Maintenance purposes Im changing the plugs. I started the thread just to get an idea of when others do it.

(ralph) · (ralph) **Join Date: Apr 2002** 11-23-2006, 6:19 PM

I changed mine at 300 Steve. I couldn't find the platinums here so I just put the copper ones in and I haven't changed them again yet. 420hrs so far so good.

(stevev210) · (stevev210) **Join Date: Feb 2005** 11-23-2006, 7:01 PM

Darren I got mine off ebay. Set of 8 for $40. Theres a guy selling 8 right know for $27.50. If you buy them from merc they want $17.45 a piece and auto stores want $10 a piece. Just type in 41-932 spark plugs.

(fill_er_up) · (fill_er_up) **Join Date: May 2006** 11-24-2006, 6:13 AM

Best way to determine exact plugs you need?

(byrd) · (byrd) **Join Date: Dec 2005** 11-24-2006, 6:25 AM

Owner's Manual....

(norcalmalibu) · (norcalmalibu) **Join Date: Jun 2004** 11-24-2006, 10:50 AM

pull a plug

(guido) · (guido) **Join Date: Jul 2002** 11-24-2006, 12:51 PM

Yeah, you could pull a plug and look at the numbers then a auto parts store should be able to cross reference. I took the plugs out of my Sanger (platinum) around 350 hours and they looked new. I changed them anyway. I supposed copper plugs would probably be due between 200 and 300. I'd imagine the platinums could go to close to a thousand if you were comfortable with it.

Incidently I just hit 100 hours on my truck and it hasn't broken 5,000 miles yet. You figure that platinum plugs are usually recomended at 100k intervals in cars, so that'd be somewhere around 2000 hours. A boat is generally run harder so I wouldn't imagine they'd last that long, but I'd say 500 hours would be a very safe, conservative number.

(bftskir) · (bftskir) **Join Date: Jan 2004** 11-24-2006, 3:18 PM

We just changed the plugs on my buddies Sanger DXII with 950 hours on it. They had never been changed. We did the cap and rotor too.
A good source for parts and repairs is Topside Marine in San Jose, Jim and Bill will get you your stuff.