Mercury 225 EFI Spark plug wires

[44Mag]

Mercury 225 EFI serial number OT121338. I recently completed a full rebuild on this engine and realized I am running this with spark plug wires that are literally 21 years old. In the automotive world, common sense would tell me that I should be replacing these wires even though I do not have any known issues with them. I am looking for any suggestions on replacing these wires as far as do people usually make their own, order OEM, they are a very short wire with a boot and terminal on the plug side, and the coil side just slides into the coil and is pierced by the pin inside. These seem like they would be very easy to make if a guy had the correct materials. Just looking for suggestions, I want to complete the job correctly the first time. Thank you in advance.

[EuropeanAM]

They actually thread into the CDM's.

OEM wires are available, of course... if you drop Rhonda an email she can certainly assist you with that.

[Slim95]

I ordered an automotive set (moroso) for my 250xb from summitracing and cut them to the same length as the factory ones. Everything worked out great and have a little over a year on them. I came from the motorsport industry and most teams ran moroso wires so that's my main reason for choosing them.

https://www.summitracing.com/parts/MOR-72510

[lpugh]

MSD are far better wires, but be sure they have the correct resistance per foot

[44Mag]

Thank you everyone for the responses. My general thought on most parts is OEM is probably best, but when it comes to plug wires that sometimes just is not the case as there has been many advances in materials in the last 20 years. Here are my thoughts on this and I am wondering what others think or what your experinces may be. The OEM wires that are on it are an 8mm solid core wire. These offer very little to no EMI and RFI protection to the ECM's but are capable of delivering a very high voltage charge, as they have very little to no resistance in the wire. Probably the best choice for all out performance, but are they the best choice for the ECM's? It has ran fine for 20 years, they do not "seem" to cause an issue on this engine. The next best alternative is a spiral core plug wire, such as the Moroso wire set that Slim95 sent the link for. These do have some RFI and EMI protection built in but still offer a very low resistance, 800 Ohm per foot, and on such a short wire the resitance maybe just enought to help and not hinder performance, this may be the route to go for the best of both worlds. Also with the spiral core, it should twist down onto the CDM stud properly as it actually does have a metal "spring like" sprial core running thorugh the middle. Moroso is also one of the very few companies that are still offering a solid core wire option. I did look at MSD as i know they make an excellent product, but they do not offer an 8mm wire in solid core any longer that I can find. Most of their selection has went to 8.5mm which will probably not screw down into the CDM's. So this leaves me looking at three options, 1) OEM Mercury wires 2) Moroso Solid core 8mm wires or 3) Morosso Spiral core 8mm wires. Which would you choose and why? What have you used and what were your results?

[electric fish]

I’m of the opinion that if It isn’t broke then don’t fix it. New technology is great but it sounds like the old tech held up very well. It’s ran good for 20 years on OEM why change? I would go with new OEM.

[EuropeanAM]

I'd stick with the originals- combined with the CORRECT Spark Plug (Champion QL77CC).