Spark plug + ignition info for 1979 Merc 45 4.5hp outboard

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ncpi

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We are trying to bring a 4.5 hp Merc outboard back to life. Sometimes it runs well, sometime it won't start. We believe we have narrowed it down to the ignition system. I have looked online and in this forum and have not found the info we need.

1. What is the recommended spark plug for this engine?
2. What is the point gap setting?

Also is there a good source for electrical/ignition parts for these? Neither mariineengines, oldmercs, nor iboats seem to have many parts.
 
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carholme

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ncpi

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Re: Spark plug + ignition info for 1979 Merc 45 4.5hp outboard

Gerry,

Thanks a bunch! We are starting with the easy stuff...the wiring and the spark plug and points gap. My concern is if we need the coil ($75 on your link) or the electronic module (not available that I have found). This engine is very hard to get at to diagnose as the recoil starter is integrated in the cover so you can't easily pull it over, start or run with the cover off.
 
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ncpi

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Re: Spark plug + ignition info for 1979 Merc 45 4.5hp outboard

Well... after looking at the manual pages, it doesn't list the 1979 4.5 HP model, looks like older engines. I now think I have found the spark plug info elsewhere; NGK BUHZ-2 or alternatively a Champion L78V, but don't know the spark plug gap. The points gap shows 0.020 on the older engines in your manual...but I don't think those have the electronic module.
 
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ncpi

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Re: Spark plug + ignition info for 1979 Merc 45 4.5hp outboard

ouch...crowleymarine wants $133.25 for contact points! Must be a less expensive source...anyone have one?
 
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River Boy

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Re: Spark plug + ignition info for 1979 Merc 45 4.5hp outboard

ncpi said:
ouch...crowleymarine wants $133.25 for contact points! Must be a less expensive source...anyone have one?
Click to expand...



Naw, you can buy Sierra after market points for it right here on I-Boats or other places for 20 bucks or so. They work plenty good enough. The plug Mercury spec'ed for that motor has no electrode arm so it doesn't gap. Auto parts houses sell them cheap.

If it says 45 on the cowl it is a 78 or earlier.
If it says 4.5 on the cowl it is a 79 or later.
With these Mercs have your serial number on hand when ordering parts.
 
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carholme

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Re: Spark plug + ignition info for 1979 Merc 45 4.5hp outboard

If you just click on the picture of the sparkplug, item 17, you will see that it is a surface gap plug.

What is the s/n of your engine?

Gerry
 
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River Boy

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ncpi

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Re: Spark plug + ignition info for 1979 Merc 45 4.5hp outboard

Cool. Didn't think of Amazon or eBay. Funny how I am happy to find a set of points that is "only" $30. Yikes. Does the 0.020" gap sound about right on this? I am hoping its not the coil or module. Since its intermittent, guess I should look for the condenser as well.
 
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River Boy

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Re: Spark plug + ignition info for 1979 Merc 45 4.5hp outboard

ncpi said:
Cool. Didn't think of Amazon or eBay. Funny how I am happy to find a set of points that is "only" $30. Yikes. Does the 0.020" gap sound about right on this? I am hoping its not the coil or module. Since its intermittent, guess I should look for the condenser as well.
Click to expand...

Yup, .020 on the points. NCPI, check out this link. Lot of good stuff in there for you. The motor being talked about is a 7.5 Merc but it is the same vintage of motor and has the same type of ignition.

http://forums.iboats.com/showthread.php?t=567913&p=3898704#post3898704
 
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