Two different spark plugs??

[nathanhooper]

1979 90hp I-6, Two different plugs numbers. It takes a little bit to start, but it idles pretty well. All except for an occasional surge, but I think that is due to a little water intrusion on the bottom cylinder.

I thought the plugs looked different when I started pulling them out one by one to check. But it didn't hit me until I looked at the letters/numbers on them.

Three are BUHW and three are BUHW-2. No particular order on them that I can tell. I am going to guess that I need to stick with one or the other. I think. I did some research on here, but cannot find where one is recommended over the other for my particular motor. My manual says L76V, which I assume is Champion brand, and these others are Merc? Please advise on which plugs to use.

Many thanks.

 

[Fuzzytbay]

Re: Two different spark plugs??

The BUWH are NGK the others are Champions, just use the same numbers of the same brand, of your choice

 

[usskydvr]

Re: Two different spark plugs??

The BUHW-2 has a slightly larger gap from the electrode to the body. The BUHW is the correct NGK plug. ( Many Merc folks prefer NGK to Champion)

 

[nathanhooper]

Re: Two different spark plugs??

Well I went to NGK website, they say the BUHW is the one for my year model. BUHW-2 is good for 90hp after 1986.

This may be a little off topic, but seeing how I brought it up on my previous post, can there be anyway to "revive" the bottom crank seal? I am really thinking that this is where I am getting the water from. I may be completely wrong though. Could you flood the cylinder, or rather, the chamber directly behind piston with some sort of seal revive, let it sit for a while and then drain it?

I know that is not ideal, but if it is simply leaking from sitting dry for so long why not try to just revive the seal?

 

[nathanhooper]

Re: Two different spark plugs??

After some looking at a diagram of the motor, how would water get into the bottom cylinder through the lower crank oil seal? I only mention that because of the location of water and someone had mentioned it before. Oh well, I guess this is really a separate topic that needs another post.

Thanks for the help with the plugs guys. I did not see your posts till after I posted the other.

 

[Chris1956]

Re: Two different spark plugs??

Nathan, The lower crank seal sits on the exhaust extension, near where the water tube enters the exhaust extension. As such, water under pressure is exposed to the block end cap. If the seal leaks, water gets into the lower crankcase.


BTW - the lower seal (actually you should use 2 or 3 seals) is very much like a propshaft seal. I do not think any kind of chemical can rehabilate them.

 

[achris]

Re: Two different spark plugs??

The BUWH are NGK the others are Champions, just use the same numbers of the same brand, of your choice

Bollocks!!!

BUHW and BUHW-2 are both NGK. The chumpion equivalents are L76V and L78V respectively.

The difference is that the BUHW has a surface spark gap of 60 thou and the BUHW-2 has a surface spark gap of 80 thou.

You 1979 90hp inline 6 engine should be using BUHW spar plugs.

Chris......