79 Evinrude 35 - spark plug question

[CatfishMN]

Hi,

This may be a silly question, but I am going to ask it anyway. I am using the OMC recommended L78 (surface gap) plugs and the motor runs just fine. I wanted to put a resistor type plug in to see if I can clear troubleshoot some interference with my depth finder. The only ones I can find are standard plugs (not surface gapped).

Can I use conventional plugs in my motor without damaging it? If so, does anyone have a recomendation for a resistor plug?

Thanks!

 

[Vic.S]

Deleted

 

[Vic.S]

The currently recommended plugs are infact QL77JC4 which are conventional inductively suppressed. plugs. You should not use resistor suppressed plugs with OMC CDI ignition only inductively suppressed ones

L78 are not surface gapped, I guess you mean L78V although L78 were the original plugs specified. QL78V are the inductively suppressed equivalent of L78V

 

[CatfishMN]

Hi Vic. Thanks for the input. I have been using the surface gapped plugs for a couple years now with no problems. Do you think the suppressed plugs would make any difference in the capacity I mentioned with the depth finder?

 

[F_R]

The "suppressor" he mentioned is there to suppress RFI noise. In other words, it is there to prevent interference "noise" on your fish finder and radio, etc, etc. Whether or not it will suppress ALL of it, well you will just have to try it to see. "Inductive" vs. "Resistive" just indicates the method it is accomplished.

 

[CatfishMN]

Thanks. I was worried that the standard plug might damage something due to it being deeper into the orifice. Is this just silly? It won't hit or damage anything?

 

[F_R]

Your concern is valid. But it is not a problem on the motor and plugs combination we are talking about here. Unmentioned, was another subject: Heat range. But again, the plugs suggested here are proper for your motor. Just don't go off trying a bunch of other stuff. There are a bazillion different plug types.

 

[CatfishMN]

Thanks for the info. I'll try the new plugs and see if it gets rid of any of the interference.

 

[Vic.S]

Thanks for the info. I'll try the new plugs and see if it gets rid of any of the interference.

but check the connections to your sounder.

check the connections to the transducer an the powersupply.

you might consider trying a more direct connection to the battery.

difficult to know what is going on sometimes.

a friend I used to sail with had the same model sounder as I have. His would not work when powered from the yacht's circuits if the inboard diesel engine was running. He therefore powered his from the optional internal battery.

mine was ok on my yacht's power supply even though charging was from an outboard .

 

[CatfishMN]

Hi Vic. My starting battery is completely separate from my accessory battery. The outboard ignition is the only thing connected to the starting battery. All other accessories, including the depth finder, are wired to a fuse box, then to the accessory battery. I am not ruling out that either the unit or transducer is bad either.