Best spark plug for low speed

[Zookeeper1955]

I have a 1976 Mercury 7.5 I use primary for slow speed trolling .
This motor has gap less plugs Champion 833M L78V plugs installed was wondering if a hotter or a gaped plug would help the motor run smoother at trolling speeds and if I could get a recommendation for the best plug < make number > that would offer the smoothest operation at lowest RPM for my motor ?

Carb is clean gas is fresh and running Sea foam mixed in the gas .

Thanks
Ken

 

[Zookeeper1955]

Re: Best spark plug for low speed

I installed a pair of NGK BUHW-2 seems a bit harder to cold start may be running a tad smother at ideal ?
Any one know witch of these 2 would be hotter the Champion 833M L78V or the NGK BUHW-2?

Thanks
Ken

 

[Mi duckdown]

Re: Best spark plug for low speed

Stop using sea foam. Fresh mixed Gas.

 

[Texasmark]

Re: Best spark plug for low speed

Stop using sea foam. Fresh mixed Gas.

Nothing against fresh gas but I don't agree with the rest of the statement. I was introduced to it years ago on this site and it has proven itself to me time and again in all sorts of engines. I always add it to my fresh gas. Just took my carbs off a 10 year old engine and bowls were spotless.

On using a different plug, I went through that several years ago. As it turned out I had a bad CDI. In the fixing process and reading up on spark plug attributes and usage, I agree with most 2 stroke marine engineers in that surface gaps and CDI ignitions are the way to go. One thing is the gap on most conventional plugs is .040". The gap on my SG plugs is .060. Lots more energy in the spark to blow across a crudded insulator. I proved that by comparing the spark between the two types and the intensity of the SG was significantly higher.....made a much bigger snap also.

However, for my engine the lower hp 3 cyl engines use the NGK BUHW-2 Surface gap whereas the 4 cylinder higher hp engines of the series lists the NGK BP8H-N-10 conventional with a gap of .040". Beats me why the change, but the 4 cyl engines do drop 2 cylinders at low rpms and that may have something to do with it. I didn't design the engines so I don't know.

Mark