1989 7.4 Plugs ?

D

darimont

New Member
Oct 13, 2006
16
Aurora, Illinois
Anyone know what plug this motor takes? I want to pick some up on the way home and the man. is in the boat and I can't remember if its an MR43T or MR44t. My local Murry's has both.

Thanks
Dan
 
champion RV15YC4 or Autolite AP-25. gap is .035". i've now entered my third season with the autolites and the boat continues to run flawlessly. you can get them at walmart for less than $1.50. i'm not familiar with the plugs you mentioned above.
 
The plugs I listed above are AC. I think I my try NGK this year. They have a listing for my engine BR6FS. I have not had good luck with Champs or Auto lites is GM engines. They seem to work for you ok.
 
hi dan
i took the champions out of the boat and replaced with the autolites. my buddy (markd on these boards) has the same engines as us and he's been using the champions for about 7 years without incident. have you considered or tried platinum tip plugs? i never tried them, but i have to say i'm very pleased with the autolites.
 
dan
i stand corrected. plain old copper core 25s.
 
Plugs

Dan,
I have an 1988 340 with 7.4's, my Mercruiser manual mentions AC plugs MR43T, this is a plug designed for Marine applications. I am sure all the others mentioned will work well, but I always have used MR43T Plugs with good results. I believe they have more longevity. My last set was changed after 6 years of use, I adverage 50 to 75 hrs per season. I only changed them because it had been 6 years and maybe I was stretching it abit. My engines run just as strong and beautiful now as they did before I changed the plugs. I have had the same experiences over a 15 year peroid with my previous boat using these plugs.
No, I am not an AC Salesperson, just a satisfied customer.
Good Luck in your choice.
 
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