1978 Mercury 800 which plugs are best

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TDramrod

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I have a 1978 Merc 800 80 hp that I bought with Perma gap plugs in it. Are they the best plug for this motor or can anybody recommend something better?
 
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Chris1956

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Re: 1978 Mercury 800 which plugs are best

I never heard of a recommeded non-surface gap spark plug for that motor. You do have a choice of equivalent plugs from different manufacturers. Autolite, NGK, Champion make them. Merc probably recomends the NGK BUHW or BUHW-2, but you should verify.
 
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stickerhard

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Re: 1978 Mercury 800 which plugs are best

I have a 1979 80 hp and thats what I have always run in it.
 
hotrod53

hotrod53

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Re: 1978 Mercury 800 which plugs are best

My '77 Merc 500 Thunderbolt has a decal right on the block saying that it recommends the surface fire type
 
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ThumbPkr

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Re: 1978 Mercury 800 which plugs are best

I would be afraid of interference between the plug and the piston with a conventional plug installed.I don't know that to be the case but I would be aware of it.Merc says the plugs are good unless the center electrode have eroded to a certain amount specified in the manual.
I have never changed the plugs in my '69 650.Ron G
 
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Chris1956

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Re: 1978 Mercury 800 which plugs are best

The pistons would not hit the ground strap of a conventional plug. Merc simply designed the motor to work with the surface gap plugs, and has never recommedded anything else.
 
Gibbles

Gibbles

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Re: 1978 Mercury 800 which plugs are best

I like the NGK surface gap my self, starts easy and runs well with them.
 
Faztbullet

Faztbullet

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Re: 1978 Mercury 800 which plugs are best

That motor requires NGK BUHW-2 plugs.
The pistons would not hit the ground strap of a conventional plug.
Click to expand...
Only if the short plugs like a J4Jor J6J where installed, L77j4C's will hit every time at about 3000rpm.
 
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Sprky

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Re: 1978 Mercury 800 which plugs are best

Chris1956 said:
The pistons would not hit the ground strap of a conventional plug. Merc simply designed the motor to work with the surface gap plugs, and has never recommedded anything else.
Click to expand...

We have run the QL78YC projected tip plugs in the L6's without issue. We were running in a class that limited modifications so we were looking for every "enth" we could get.
 
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