How often do you change your spark plugs?

[Lovetoski]

Curious how often people are changing their plugs? Bought a used boat engine had only 130 hours (replacement in 03). I had to change the plugs because of no power out of the hole and lower top end speed than I should have been getting.

I first changed fuel filter, cap, rotor, then ran seafoam, then changed plugs....plugs "fixed it". But then I am wondering why these plugs were so bad and if they are going to "refoul" due to something causing it...what causes plugs to foul? How many hours before they need to be changed?

Engine was replaced because dealer "forgot" to winterize it...dealer now out of business big surprise...what if they put the original plugs in new engine to save a dime? That is the only reason I can figure these plugs would be so bad?

Just looking for input...in time I am sure it will tell if something is causing plugs to foul...they were marine plugs.

Thanks!

Edited June 23, 2011 by Lovetoski

[cbmalibu98]

I change plugs and wires, cap and rotor every 100 hours. I know that is over kill but we put about 50 house a year on our ride. It is a small amount of money for the piece of mind.

Good Luck

CB

[davemac]

It depends on whether or not you are running the expensive $10+/each Iridium ones (which last much longer). I switched to the NGK TR5 (about $2 or $3/each). I generally put 50-70 hrs/yr on the boat, and usually change them after a few times out in the Spring (to make sure the winter's fogging oil has been burned off). If they don't look bad, I'll stretch them out....but no more than two seasons....especially when you can replace them all for <$20.

IIRC, the Iridium ones are rated for 500 hrs or so. I'm not sure if the expected lifespan is compromised by gunking them up w/ fogging oil at the end of each season.

Edited June 23, 2011 by davemac

[Lovetoski]

OMG! Thank you....wow I had no idea that people changed them that often! Well that explains a lot! I just put the NGK ones in when I took the Delco out.

Here is something I found interesting too...it is a diagnosis of why your spark plug could be fouled:

http://www.gnttype.org/techarea/engine/plugs.html

Thanks for your responses!

[wdr]

There are a lot of smarter guys than me on the site IRT this, but the way I understand it is the main reason to change a plug(s) is electrode erosion which changes the gap & performance. First thing I would do is cross reference the plugs to see if they are correct for the engine (heat rng/reach /gap). If they are run it and monitor them to see how they look. Most places advise that if the plug color is a light cocoa brown it signifies a normal condition, cylinders will vary. Another reason to change them and this was/is common to those of us that ride carbed Harleys is to get the correct heat range for a given engine. Too hot a plug can cause internal damage and too cold could foul the plugs. If your former dealer was just looking to be rid of you and reduce overhead at the same time they may of just put whatever plugs they had laying aroung in the engine. Which means the plugs could of been the wrong heat range, wrong gap and or wrong reach into the cylinder which could show fouling. I normally check mine every winterization and change them every 3 years needed or not. Now days most car plugs are good for 50k or better, granted boat service conditions are different but I don't think so different as to require changing plugs every year. But if it makes you feel better it is one of the cheaper "piece of mind" acts that you could do on a boat. Good luck.

[Chia]

an idea might be to follow the indmar manual:

[Murphy8166]

I do mine every year no matter how many few hours

I can go to napa auto parts are get both fuel filters, cap, rotor and plugs for under $60. Engine is a Monsoon one so plugs are 2.19 a piece

[cbftbl87]

Curious how often people are changing their plugs? Bought a used boat engine had only 130 hours (replacement in 03). I had to change the plugs because of no power out of the hole and lower top end speed than I should have been getting.

I first changed fuel filter, cap, rotor, then ran seafoam, then changed plugs....plugs "fixed it". But then I am wondering why these plugs were so bad and if they are going to "refoul" due to something causing it...what causes plugs to foul? How many hours before they need to be changed?

Engine was replaced because dealer "forgot" to winterize it...dealer now out of business big surprise...what if they put the original plugs in new engine to save a dime? That is the only reason I can figure these plugs would be so bad?

Just looking for input...in time I am sure it will tell if something is causing plugs to foul...they were marine plugs.

Thanks!

My manual states every 300 hrs for plugs. But that is for EFI. If it's carb, i'd do it once every year or two.

When I bought my boat last year, it still had the original plugs in it from 1995, lol. Needless to say it needed a tune up.

[Lovetoski]

That is nice to have. Thanks I printed it

an idea might be to follow the indmar manual: