787 running hotter plugs, good or bad?

[TerrenceBennett]

I have a 97 Challenger jet boat powered by a single 787 110hp. It’s running a little rich and leaving the plugs, wet fouled by the end of the day (about 2-4hrs, most of the time 5-7,000 RPM)
I have read going a little hotter plug could help but I also read running to hot a plug can melt of overheat the engine. They weren’t too specific about the hotter plugs. I was thinking and I maybe wrong that running a BR7ES or BR6ES would be alright? I’m looking for advice on just how much hotter I can go without causing (any) damage.

 

[Dr Honda]

Running a hotter plug can lead to pre-ignition. And, that can burn a hole in your pistons.


If you are running rich... fix the problem. "8's" will run perfect in these engines. Besides... if you are always fouling plugs... you are rich to the point, where you will "Wash" the pistons, and can starve the engine of oil.

 

[TerrenceBennett]

How do we know how hot 7s are in relation to 8s.

Carbs are not the only possible problem, it could be pop off pressure caused by a aftermarket flame arrestor or lack of one. I have one, but ordered a SEDOO original one to replace it first, because I don’t know the previous owner. This is why I collect all the available information I can, before I jump off. Can you tell me the heat range of a 8 vs 7? and a 6 vs 8?

 

[Dr Honda]

How do we know how hot 7s are in relation to 8s.

Honestly... you don't. It's relative to each series of plugs. AND... it's not like a thermostat that you can say... "it's a 180 degrees."


Going one step hotter generally won't cause issues, and it can be beneficial to tuning. But... there are thousands of seadoo/rotax engines running perfectly fine on 8's.

 

[TerrenceBennett]

Thank you very much. I have a long list of things to do and check out but though I’d plug chop to see if this problem could be put off till after season. My big problem is the mid-range of the boat, I don't have one!, it either Idle or go and that makes wake boarding very hard. Again thanks for the Info and if you can think of any thing for my problem, I'm all ears.

 

[Sportster-2001-951C-Stock]

Sounds like your carbs are goofed up and too rich, could be other things going on too, like an oil pump adjustment is way off if someone's been in there who didn't know what they were doing.

I think you'd be doing well to check everything, tear the carbs down and blueprint them. Good opportunity to replace fuel lines as well, they rot over time.