Plugs and wires 1972 Stringer NLA?

[southkogs]

Last weekend on the lake lost a buncha' power on the way back in and got a constant "popping" noise (not like a backfire, quieter than that). No smoke, big booms or anything of that nature and she'll idle just fine (albeit with the popping noise).

1972 OMC inline 6 (Chevy 250 / JUFM-10S)

I pulled the first two plug wires and turned the engine with a bare plug in 'em - nothing. Third one on back gives me a spark when I do it. So I'm figuring I'll start with new plugs and wires as I've not changed them yet since owning the boat.

Here's the hitch - so far, it looks as though most of the plug wires are no longer available for this model? Am I missing something (non-mechanical guy here)? Is there a way to substitute (as in plugs from a newer OMC that would work)? As I understand it using automotive wires is no good, correct?

Thanks in advance.

 

[Howard Sterndrive]

Re: Plugs and wires 1972 Stringer NLA?

automotive wires fine in my opinion.
they live in a much harsher environment than a boat.... hot exhaust/cold weather/etc...
for my V6, I bought a nice set of 7mm wires for an old chev 350 with point ign. (Chevelle, Corvette pre 73), used what fit best, and kept a couple wires as spares.

 

[cr2k]

Re: Plugs and wires 1972 Stringer NLA?

The HP wire set for the L6 is still listed in my Sierra book.

18-8809 Available thru NAPA.

 

[southkogs]

Re: Plugs and wires 1972 Stringer NLA?

Thanks to both of you ... I'll check NAPA in the morning. The online store wouldn't pull it up for me. I'll see if the local guys can pull it off. If not, I'll go with the automotive stuff for the moment.

 

[southkogs]

Re: Plugs and wires 1972 Stringer NLA?

Put new wires on and still not getting spark on #1 & #2. I'm actually wondering if I've been running short a cylinder for a little longer than I (Mr. Mediocre-wrench) realized. So, I'm thinking my problem is in the distributor.

This one is still points, and I've read posts about changing over to a different type - any major value in that? Current set-up is easy enough for a two-thumbed mechanic like me to get, but if there is a major benefit to changing over now might be the time.

Let me know your suggestions, and thanks!

 

[Howard Sterndrive]

Re: Plugs and wires 1972 Stringer NLA?

there's only one set of points - and they're the same points that make the sparks on the other 4 cylinders.
I think you need to keep looking for the problem.
Rotate the engine slowly and watch the point cam to make sure it opens and closes the arm 6 times in two revolutions of the engine.
Have a good look at the distributor cap.

don't change any parts until you understand the problem

 

[southkogs]

Re: Plugs and wires 1972 Stringer NLA?

I think you need to keep looking for the problem ... don't change any parts until you understand the problem

WILCO. I planned on being pretty much in dry dock all of July due to travel plans, so I can be patient and figure it out right.

Rotate the engine slowly...

I have never done this. Can you give me a quick primer on doing it? I'll Google it too ...

... and thanks as always.

 

[Howard Sterndrive]

Re: Plugs and wires 1972 Stringer NLA?

some use a strap wrench on the harmonic balancer. I usually just use a wrench on the alternator and sort of push on the belt and roll it at the same time.

 

[southkogs]

Re: Plugs and wires 1972 Stringer NLA?

Okay - I was having trouble turning the engine by hand (I'm not doing something right), but kinda' cleaned up the distributor a bit.

I didn't see spark on #1 at first, but after checking the other wires using a bare plug I think I've figured out that I'm getting spark on all 6. The boat will start and run, but it runs rough. In the driveway I think I can hear it missing, but the exhaust is too loud to hear the sound that's really bugging me. When I put her in the water, I can hear a "popping" sound when I throttle up. The engine is running so rough that you can feel the vibrations throughout the boat.

The engine oil is a little dirty, but it's not milky. No steam that I can find/see/smell. Nuthin' seems to be burning.

Honestly, I'm a little lost here. Any suggestions?

 

[Howard Sterndrive]

Re: Plugs and wires 1972 Stringer NLA?

start with a compression test I suppose... could adjust valves too while compression testing. (I like to verify valve settings with compression test to make sure none hanging open or rockers overtight)
have a look at the heat tube for the choke or any other areas a vacuum leak could occur- base of carb etc

 

[southkogs]

Re: Plugs and wires 1972 Stringer NLA?

Okay - did a compression test (twice actually to make sure it was consistent): #1 - 90 / #2 - 0 / #3 - 0 / #4 - 90 / #5 - 90 / #6 - 90 (wasn't exactly 90, but within a couple of lbs.)

I know that's not good ... but it's over my head. Rings or head gasket as a guess, correct? If so - how big a project is it? Seems like it'd be easier than on a car ... is it worth doing?