300 more rpms spark plug change

F

freddyray21

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Jun 10, 2006
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2,460
I have been reading some of the posts concerning spark plug types and what to use or not to use. I did have AC Delco plugs in my 120 hp Mercruiser and was taching 4000 wot with it. (tach is a bit off using a shop tach is it about 4200) I put in a set of NGK's and am now taching 4300 or about 4500 rpms. That is the only thing I did was change plugs.
 
J

jimhen

Seaman Apprentice
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Jun 7, 2007
Messages
44
Re: 300 more rpms spark plug change

sounds good to me. I'm just getting wet ( next week maybe ) and I put in NKG 's for the first time. Hope to confirm your results!
 
bruceb58

bruceb58

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Mar 5, 2006
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30,802
Re: 300 more rpms spark plug change

Was this done on the same day?

Same temperature?

Same humidity?

Same water conditions?

Same drive trim?

Same wind?

All could make a difference. Assuming the last spark plugs were still ok, I really doubt it was the spark plugs.
 
Don S

Don S

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62,321
Re: 300 more rpms spark plug change

and how old were the AC plugs you took out.

Read the post at the top of this forum. Complete tune up every spring..... Why, fuel economy and it makes the boat run better.
 
F

freddyray21

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Jun 10, 2006
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Re: 300 more rpms spark plug change

plugs were new middle of last year and looked good when I took them out to replace them. Ignition is petronix electronic. No not done on the same day or even the same lake, but I've been taching out at the 4200 since putting the old plugs in.
 
pete44

pete44

Petty Officer 2nd Class
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May 7, 2005
Messages
189
Re: 300 more rpms spark plug change

Don S said:
and how old were the AC plugs you took out.

Read the post at the top of this forum. Complete tune up every spring..... Why, fuel economy and it makes the boat run better.
Click to expand...



I know I have read you fog the engine before winterizing...(including sparkplugs and their associated ports/cylinders...then it recommends to run same plugs ONCE after de-winterizing...then CHANGE them..a ONCE a year thing.....Just my 2 cents worth....Pete
 
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