right spark plug for 115 2+2 Mercury 1993

[dlaxdal]

Is the NGK BP8H-N-10 the right plug for a 1993 mercury outboard 115 2+2?????

Thx

 

[sschefer]

Re: right spark plug for 115 2+2 Mercury 1993

Yes, you can also use the perma gap plugs but I've never had much luck with them in mine. I gap the plugs at 040. like the book says.

Just curious, how does yours run?

 

[dlaxdal]

Re: right spark plug for 115 2+2 Mercury 1993

I am not at the boat right now but it was running ok until they took it out the other day and it ran rough at high rpm's . I will put these recommended plugs in

 

[CharlieB]

Re: right spark plug for 115 2+2 Mercury 1993

I' d have to check the book for a 93, but my 96 calls for a BPZ8H-N-10, an expensive (12.00) plug which is nothing more than an extended tip plug pre-gapped at 10 cm and an expensive iridium electrode. The precious metal is not really necessary, I run the BPR8HS and set the gap at .032 at under 2.00 each and change them annually, it runs just fine.

 

[dlaxdal]

Re: right spark plug for 115 2+2 Mercury 1993

I will check the mercury dealer to see what plug they recommend

 

[sschefer]

Re: right spark plug for 115 2+2 Mercury 1993

Good Idea....

 

[sschefer]

Re: right spark plug for 115 2+2 Mercury 1993

I' d have to check the book for a 93, but my 96 calls for a BPZ8H-N-10, an expensive (12.00) plug which is nothing more than an extended tip plug pre-gapped at 10 cm and an expensive iridium electrode. The precious metal is not really necessary, I run the BPR8HS and set the gap at .032 at under 2.00 each and change them annually, it runs just fine.

Charlie you have a 96, what does the book call for as far as gap. Mines a 93 and it calls for .040 gap and if you look up the plugs you can get a mix of repsonses but Merc and NGK say to use the BP8H-N-10 in the 2+2's. Do you feel these too would benifit from by closing the gap to .032 on the plugs.

 

[CharlieB]

Re: right spark plug for 115 2+2 Mercury 1993

Actually, the wider the gap the hotter the spark, and the better the ignition of the fuel.

I haven't taken the time to test and see if there is a measureable difference in performance. Possibly a very small % WOT RPM.

.032 - .035 has been a standard gap for many ignitions for a very long time.

With the advent of EPA, emissions standards, and electronic injections, manufacturers have been struggling to build leaner, cleaner burning engines and those mixtures require significantly hotter spark to ignite.

Our carbed 2-strokes are NOT lean-burn engines. Hence, our future is certain to become limited, it's just a matter of time.

 

[sschefer]

Re: right spark plug for 115 2+2 Mercury 1993

Charlie I agree on the future of these older carbed engines. Mines a 91 Mariner 2+2 and the shop manual (not Seloc or Clymer) say's .040 for the gap. I suspect that the fact that they run on two fairly rich cylinders up to 1800 RPM's and then the air/fuel ratio on the other two cylinders becomes adequate to ignite. We'll that's the way it's supposed to work but I'm finding that getting that perfect balance is extremely difficult even on a fresh rebuild with 135lbs of even compression.

I run the n-10 plugs vs. the BUHW perma gaps that they say are the norm. The perma gaps just seem to foul too easy so I'm thinking that if they have a problem then closing the gap would probably produce similar results and the person that started this thread might become as frustrated as I have over mine.

This engine design is really a failed attempt to produce a big trolling motor. It reminds me of the 4-6-8 Caddies of years gone by. The folks that make aftermarket parts seem to think my motor is the same as a standard 115 so I have to go directly to Merc for my parts (lessons learned). Even then, many of the parts manuals don't recognize the difference and you still end up with the wrong parts.

Top that off with a sand hole in the block like I finally found in mine and these things will drive you nuts. Mines getting sold for parts and I'm dropping my F-150 Yami on the boat to finish out the year. Thank God I bought it with controls but now I have to tear into the boat again.

There, I've vented about my 2+2, dlaxdal if you're in a similar situation please note the final solution. It is one you will face sooner or later.