Black Carbon Plugs
 

My Hp500 started up this season with no problems. The motor has 132hours on it since new. After 1/10 of an our it started running rough and missing, it stalled a few times. I got it back to the dock and on the trailer. I pulled the plugs and they were carbon filled. I changed them out and put in ne AC DELCO Mr43T plugs. The boat ran great for the rest of the day. The boat sat a week. I started the boat and it ran a little rough, skipped a few times. Then was ok, ran it for another 15 minutes or so and decided to pull a plug. The plugs were all the same as before, dry carbon, solid black., the plugs are the correct ones, the wires are new, cap and rotor are also. Could the choke be causing this, or is the carb out of adjustment?? Any help would be greatly apreciated. I know the motors are better running a little rich but I should fol plugs after 15 minutes.

Re: Black Carbon Plugs
 

Could it be the choke heater, if so how can I easily check it? Or doesn't this sound like a choke issue

Re: Black Carbon Plugs
 

I Don't Use Mr43t In My Hp's Use Ngk-ur5(v-power)
Much Better Plug And Once The Motor Warms Up
Take The Air Cleaner Off And See If The Choke
Is All The Way Open. I Took My Choke Off.

Re: Black Carbon Plugs
 

I do use MR43's in mine and have never fouled a plug. I would also start looking at the choke.

Re: Black Carbon Plugs
 

Could the choke just be gumed up, should I spray some choke cleaner.on it.

Re: Black Carbon Plugs
 

let the motor warm up and take the air cleaner off and the choke should be open. if it's not then thats you'r problem.

Re: Black Carbon Plugs
 

Idle mixture is too rich causing your plugs to fowl. Turn in your idle mixture screws and back out 1 1/2 turns to start. Use a vacuum gage to obtain maximum pressure. Make sure that you set all of the idle screws and don't forget to count number of turns in.

Re: Black Carbon Plugs
 

How many idle mixture screws are there

Re: Black Carbon Plugs
 

Just get a small wire tie and wire the choke open. See if it solves the problem and go from there.

Re: Black Carbon Plugs
 

Do you have fuel pressure guages? If it's a mechanical fuel pump soemtimes they make to much pressure as they get old and will push fuel passed the needles and seats in the carb. Just had one do it changed the fuel pump and all is better.
Oh ya the fuel pump was a Holley only 1 year old.

Mark