Spark plugs and socket wrench Mercruiser 5.7 Alpha 357

[Ramanonos]

I wanted to check my plugs, but I can't seem to get a fit with a standard car socket wrench. Is there a special kind of wrench/socket for this engine? I had a similar problem with my motorcycle and bought a thin walled socket at the hardware store. No luck on the merc 5.7.

Also, does anyone know the type of spark plugs I should use (and spec gap)? I can't seem to find this information in the owners manual. I have a refurbed Merc 357 5.7L Alpha carb. This is just a GM motor, yes? So I should be able to pick that up at any auto parts store? Wasn't sure if there are special Merc marine style plugs I should be using. I'm not really close to a marine store. Thanks!

 

[haulnazz15]

Re: Spark plugs and socket wrench Mercruiser 5.7 Alpha 357

I'm not understanding your problem. Is it that you can't get the correct size socket, or that the socket is too tall to clear the exhaust manifold? Easy solution, use a box wrench instead of a socket wrench. Tougher solution, remove the socket from the wrench and put in on the plug, then attach the ratchet. Regular automotive plugs. There's no such thing as a marine spark plug for that engine. It runs the same way a car engine does.

 

[Don S]

Re: Spark plugs and socket wrench Mercruiser 5.7 Alpha 357

I know what the problem is, he has those mid 80's style that I called bubble manifolds. (Notice we get no clue as to the year of his engine :facepalm: ). They are really rounded on the edge and get real close to the spark plugs. Even worse if you have the long spark plugs like Champions.

Make yourself a spark plug socket from a regular spark plug socket like this.



Also use a shorter spark plug, like AC or NGK.

 

[Ramanonos]

Re: Spark plugs and socket wrench Mercruiser 5.7 Alpha 357

Got it. Just needed a a thin walled long socket. Auto parts store has them.

 

[grewvin1]

Re: Spark plugs and socket wrench Mercruiser 5.7 Alpha 357

nope you need to use Don's sketch and turn down a plug socket to the taper shown or the water jacket will bind on the socket. I have twin 5.7L and it is the only socket mod that will work.

 

[Scott Danforth]

Re: Spark plugs and socket wrench Mercruiser 5.7 Alpha 357

getting out the old plugs is easy, just smack the isolator and snap it off. putting them in you need to taper a plug socket like Don's sketch. you can use a bench grinder to taper the plug in about 5 minutes. just have a bucket of water handy because it gets warm fast.

I also recommend the NGK's

 

[swainner]

I had a similar problem on my 96’ 5.7L Mercruiser. I took a standard 5/8 socket and cut it in half. Then I ground a hex shaped head on the end of the socket. At that point, I could easily put the socket over the plug head and use a crescent wrench to back the plugs out. I recommend using a closed head ratching wrench as there is very little turning radius on some of the plugs locations. Using the crescent wrench limited my points of placing the wrench on the socket head

 

[aimlow]

Re: Spark plugs and socket wrench Mercruiser 5.7 Alpha 357

getting out the old plugs is easy, just smack the isolator and snap it off. putting them in you need to taper a plug socket like Don's sketch. you can use a bench grinder to taper the plug in about 5 minutes. just have a bucket of water handy because it gets warm fast.

I also recommend the NGK's

I'll bet you subscribe to the "float test" for good used plugs. Throw 'em in a bucket of water..the good ones float.

 

[Bt Doctur]

this thread is 6 years old , pleas start a new one with your own issue .