NEED HELP Marine Power 340 running like crap

[adamsjstt]

I have cheched and rechecked the firing order

[adamsjstt]

So I started to remove my fuel injectors to send them out and have them cleaned and flow tested when I noticed something that caught my eye. the top of the distributor cap has the cylinder numbers stamped next to the outlet where you plug in the wire. If you look close at the picture you will see that on the right side of the cap the number 8 is on top number 2 is right below then 4 and 6.Well what caught my eye was the path that number two takes from the rotor across the cap to the plug wire and how close number 2 and 8 run next to each other and I remembered a post from dom about bad caps and that they miss fired thru the plastic so I decided to remove the cap and it is obvious that where number 2 and 8 are at there closest number 2 is passing thru to number 8 and exiting the side of the cap. So I reinstalled my old cap and it seems to idle much smoother so hopefully I found the issue but wont be able to lake test for a couple weeks.

[SPBFAN]

Where are you located in Central CA. I would love to help you get this going. The time will be off on the engine if you do not have the knock sensor hooked up. I am sure this is a correctable problem. I do have scan equipment and I am very confident we can get you going. I will PM you my number. I am located in Bakersfield, CA. I have all the fuel injector cleaning tools, No need to take the boat apart. We can do it on the boat if needed. Sorry I did not catch this post earlier.

[adamsjstt]

Well so much for that conclusion. I returned the cap to napa and what I thought was a burn spot on the outside of the cap by number 8 plug wire is just a break apart point to seperate the caps as they come off the production line. It seemed to be the obvious answer and still could be. Napa exchanged the cap so I will try it again. I will also be contacting andrew for some help.

[SPBFAN]

Great to talk with you I look forward to getting your boat and looking at it. I am confident we can fix it.

[adamsjstt]

First off THANK YOU to SPBFAN, for taking the time to share some thoughts and knowledge, very helpful. So last night I installed the new distributor cap and tonight I pulled it out off the garage and attached the fake-a-lake, I think the cap was the problem. Idles smooth no sputter or missing. Ran the boat for about 20 min then pulled the plugs at #2 and #8 cylinder and they are looking alot better they have a little brownish color not solid black as before, I think after I get the boat in the water and run it with a load the plugs will clean up. THANKS AGAIN ANDREW

[Dave K]

............. I noticed the black plug on my knock sensor was broke and the plug on the wire going to the sensor was not able to clip in securely, .................

What is the BLACK PLUG and what does it do?

[adamsjstt]

I think he is referring to the electrical plug that bolts to the brass knock sensor that scews into the block.....hope that makes sense