Spark Plug Wires and Distributor - When to Replace?
 

How do you know when to replace your spark plug wires? How about the distributor cap?

My wires are probably 10 years old. The cap is probably 5 years old. Everything runs great and looks to be in good condition (no cracking on the wires).

Any hints?

Thanks!

Stevel,

I can't say there is a specific benchmark for changing them, but my general rule of thumb is that I change my cap/rotor every season. As for sparkplug cables well that is relative to how good they are to begin with, are they burned from exhaust manifolds etc. I would say I would change them at least every 3 years but no more than 5 or 6. Again it all depends on how good they are from the beginning, how much usage and how well they are taken care of.

These are items that I believe are best to change whenever in
doubt. Not hard to do and it's good insurance for a fun day of boating.

My .02

It's better to be more safe than sorry, than to ruin a great day of boating. Pantera has some good advice, I'd also recommend changing both the caps and the wires if they're that old.

I don't know if you need to change them every year after that, but at the very least inspect them annually and maybe keep a spare cap in your repair kit. In any case, make it a habit to inspect the motors regularly and look for problems like that ahead of time. Belts, hoses, wires, fluid levels and such only take a few minutes.

At least keep a spare set. The cap will turn green inside when shot. They are cheap and go right away. No warning. The wires can be seen at night while running. They will put on a nice light show if really bad. I replace mine every two years. I replace the cap when it goes and I put the backup on.

I have looked at night but I didn't see any sparks leaking. What should a good set of cables read across an Ohm meter. I am looking for something a little more scientific. I would personally guess that some of you guys that are replacing these components yearly are probably doing so needlessly. I also agree that a spare set is always worthwhile.

Thanks for your imput!

Steve

Hi Steve, no problem in providing some "imput" :D

Sorry I don't know the answer to your question about the meter and what it should read on the wires. As with anything else (like cars, cycles, etc.) everyone really has their own thresholds with regard to maintenance and breakdowns. It depends on your particular threshold when it comes to deciding how often to replace something.

When I bought the wires, I simply bought the best ones as recommended by other people with experience. I can't remember the brand, but they're about 3 or 4 years old now and show no signs of wear. They are red in color and thicker than the OEM.

For the cap, I simply bought what the local marina stocked, and I simply inspect it every season. I do not change it every season as someone else might, however I do change my gear lube religiously ever season, and my motor oil ever 40 hours. Some may feel that's unnecessary, but I don't mind, it's just my preference.

By the way, is there an "official" Mercruiser recommended interval for changing wires and caps? I'd be curious to see what they recommend, and they may even be able to tell you what the meter should read as well. See if there's anything on their site.

Whoops - the M and the N got a little mixed up there.

Thanks!