melted boots on spark plug wires! What happened? 1976 Chrysler 75 HP Model# 757HC

[bankbuster]

Hi all......Ive been working on getting this boat out all year. I had the shop check out the motor before I ran it......they tank tested it and said it was ready for the water. Well.......I took it out and it seemed to run great for the first 10-15 minutes. Then at about 80% throttle it felt like it was losing power so I threw it in nuetral. It idle fine. I slowly gave it forward throttle.....ran about 1/2 throttle for about 2-3 minutes. Then, just as a boat passsed and I approached choppy water (their waves) my engine lost power and almost died. I shut it down as I was confident that rough waters had loosened a connection somewhere. I pulled the hood and noticed my #3 (bottom cylinder) plug wire was melted just the boot). That cylinder seemed hotter than the others. Look at the pics.....is this just clogged carbs and or carbs out of sinc/adjustment?

 

[bankbuster]

Re: melted boots on spark plug wires! What happened? 1976 Chrysler 75 HP Model# 757H

Here are the plugs....top, middle and bottom. Notice the notice the disscoloring on bottom plug.....cant be good.

 

[bankbuster]

Re: melted boots on spark plug wires! What happened? 1976 Chrysler 75 HP Model# 757H

Heres the bottom boot

 

[bankbuster]

Re: melted boots on spark plug wires! What happened? 1976 Chrysler 75 HP Model# 757H

heres the bottom plug.....notice the inside thingy broke

 

[bankbuster]

Re: melted boots on spark plug wires! What happened? 1976 Chrysler 75 HP Model# 757H

and finally here is a pic of all the wires. top, middle and bottom. looks like the top cylinder was running hot as well. Also to note. I fished and trolled without starting motor for over 4 hours after this problem. Once I was back at marina I did start engine and shifted into forward just to make sure is wasnt seized. I ran it 5-8 seconds at most. Worked fine but of course I immediately shut it back down.

 

[Frank Acampora]

Re: melted boots on spark plug wires! What happened? 1976 Chrysler 75 HP Model# 757H

Well, it is obvious that #1, you are using the incorrect plugs. If your 1976 has Motorola CD ignition you need to be using a surface gap plug like Champion L20V, UL18V, L76V, or NGK BUHW or BUHX.

Notice how the center electrodes are worn way down in addition to the sparkplug boots being melted. The Center electrode plugs are too hot.

Before you do anything else, perform a compression check to be certain the plugs have not caused piston damage. Then using the FAQ sticky, perform a synchronizing and set carbs.

EDIT: I just realized that you are the one with the coil and ballast resistor. Again, the plugs are too hot but you would most likely use a bent electrode plug in a much cooler range. Surface gap plugs will in all probability misfire and refuse to start, but you can try them. OR, perhaps try the OMC QL77 plugs.

Here, with heat ranges I can not help. take your existing plugs to the auto store and get the equivalent a couple of heat ranges cooler.

And try something other than autolite--I never did like those plugs.

 

[bankbuster]

Re: melted boots on spark plug wires! What happened? 1976 Chrysler 75 HP Model# 757H

Dropping it off at the boat shop tomorrow (thats where i purchased the motor). Owner said he would check it all out. Ill update sometime next week.....hopefully Ill have it back by then...?

 

[bankbuster]

Re: melted boots on spark plug wires! What happened? 1976 Chrysler 75 HP Model# 757H

FINALLY.....I have the boat back! Shop said impeller was to blame for the overheating. I'll be taking out this sunday and update next week. Look for a new thread under "trolling motors as I need help once again! Thanks all!