PM spark plug change how often?

[HotTommy]

I did a pretty thorough rebuild on my 1993 Force 150 last year, so I'm asking this question just for info, not because anything is wrong. Some 2-cycle engines I've owned before would just stop running when the spark plugs wore out. I'd rather that not happen when I'm out in my boat. So what do the experts recommend as the interval for preventive maintenance change of spark plugs? Do you base it on seasons, hours, symptoms, or what?

 

[Frank Acampora]

The surface gap plugs simply will not wear out in a reasonable time. They will, however, foul. When the engine becomes hard to start, or will not start, or stalls when put into gear, the first thing to do is remove the plugs and clean them. Depending upon usage, the plugs can be cleaned for years before they need replacement.

They ARE worn out when the center electrode is worn below the level of the porcelain insulator.

That said, If you get the whole season without problems, clean the plugs--or replace them if it makes you feel better spending money--as part of the winterizing maintenance.

If your engine has the Mercury ignition, plugs may not last quite as long as with the older Prestolite ignition since the Mercury is "hotter." However, even with that, a yearly change could be considered overkill.

Remember also: Sometimes (rarely) a used or even a new plug simply will not fire under compression--for no apparent reason. If that is the case, you have no choice but to change plugs no matter what their condition..

 

[HotTommy]

I typically use my boat engine for about 50 hours over a four mouth span each summer. So I plan to clean the plugs each year before the season starts, and replace them every third year. Does that sound like a reasonable PM plan?

 

[jerryjerry05]

I'm REAL cheap.
I have surface gap plugs that have made the 10 year anniversary.
Some might have made it longer.
The regular with the electrode I replace every year(mower, weeder)
My V-10 Ford lasted over 7 years. Mostly cause it takes 6-8hr to change them.

 

[gm280]

I had OBs that I never changes any plugs because there was no obvious reason to do so. If your engine cranks and runs like it always has, why change anything and take the chance of unsetting the apple cart? As for my other lawn engines like lawn mower and such, I have an engine that is about 16 years old or older and it still has the original plug in it. I think I remove it about every other year and clean it up and regap and replace. It cranks so fast I have no issues with it...yet! So Change them as you think you should... JMHO!

 

[SkiDad]

my dad's boat has had the same ones for about 20 years. My boat has ones that are about 5 years old (we boat weekly) and I plan on replacing them this year and keeping the old ones in the boat for spares. I think it just boils down to preference.

 

[HotTommy]

What some of you guys are telling me is that plugs on these 2-cycle engines don't fail as frequently as the ones I had experienced in other engines I have owned. Perhaps I'll work on the premise that even if one fails while I'm on the lake, I have four more to get me home.

 

[gm280]

What some of you guys are telling me is that plugs on these 2-cycle engines don't fail as frequently as the ones I had experienced in other engines I have owned. Perhaps I'll work on the premise that even if one fails while I'm on the lake, I have four more to get me home.

Actually that is one way to look at it. Most OB engines have separate coils for each plug and that is like a built in backup to allow you to keep going (if only at a slow pace) back to the dock...

 

[jerryjerry05]

Even though my plugs are old and probably won't fail.
I still keep a new set on board, just in case!!

 

[HotTommy]

Even though my plugs are old and probably won't fail.
I still keep a new set on board, just in case!!

There is no practical way for me to access the plugs while on the water. So if it fails completely, I just drift with the breeze until I can flag down some help.