Question About Changing Spark Plugs

[Boater420]

Hello all,

I have a 1997 330 Sundancer with 7.4 Bluewater engines. I can follow the plug wires down to the spark plugs and have enough room to work in that area. My question is...Is it possible to remove the plugs without removing the manifolds. It looks like it's going to take some time and contortion on my part, I just want to know if anyone else has done it successfully.

I can see myself starting the project and finding out that there's just one plug you cant get to without removing the manifold. With my luck it would be the last plug I removed.

If it is possible, what tools? Special sockets, swivels, extensions, tips and tricks?

Thanks,

Kevin

 

[rondds]

You should NOT have to remove the manifold. Best advice I could give is to rig something up that allows you to have a platform over the engines that is movable. You will likely have to just about stand on your head to get to some of them but it's doable.

 

[Mike Blake]

Just a few extensions, ratchets and a jug of Crown Royal

 

[NorCal Boater]

When I owned my 340da I used a 16" wide plank and laid it across the tops of the engines and then I laid on top of that to change the plugs. Make sure you have a spark plug socket with the rubber inside to hold the plug, have several different length extensions and at least one universal (wobbly) extension.

Leave the manifolds alone, turn on some tasty tunes and try and have a helper to hand you things. Getting up and down sucks.

 

[vandal]

It is not that bad just a spark plug socket an 2 or 3 inch 3/8 rachet with a flex head change wires too. Do one at a time.

 

[pvan]

Changing plugs is not fun but you do not need to remove the manifolds. I suggest a plug cap removal tool about $7 at NAPA. Also get a thin wall socket with rubber plug holder. I also recommend you use dielectric grease on the ends of the new plugs before you put back on the plug wires.

 

[SloBurn]

I usually stand on my head to get at the plugs in my 7.4L. Or get my trained grease monkey down there.

 

[Air O'Nautical]

Changing plugs is not fun but you do not need to remove the manifolds. I suggest a plug cap removal tool about $7 at NAPA. Also get a thin wall socket with rubber plug holder. I also recommend you use dielectric grease on the ends of the new plugs before you put back on the plug wires.

I learned all about Dielectric grease in another thread on here someplace..
Heres a youtube describing how to use the grease and don't put it on the end of the sparkplug..

https://m.youtube.com/watch?v=-542IYGBbpg

(just in the spirit of US all learning from this web site)

 

[Boater420]

Thank you all for your tips and info. I'll be there all weekend changing spark plugs I guess. Got the plank already.

Kevin

 

[rondds]

One more thing...2 advise prior to starting. Not kidding!

 

[dvx216]

Die electric/insulating grease on the boot maybe but if you put any thing on the threads then how much you torque the spark plugs will change . The spec for dry torque on spark plugs for a Merc. 7.4 is 15 ft lb. / 20 Nm. according to Performance Product Technologies web site. If you use any thing on the treads then you can not use those specs. Why would you put an insulating compound on the out side of a spark plug threads that in suppose to be grounded to the head. Most die electric grease unless high temp is not rated for the heat it will see at the spark plug threads. Most good quality spark plug threads are treated so you do not need to put any thing on them. If you use the wrong compound at those temperatures it will harden and act like lock tight.

 

[pvan]

I learned all about Dielectric grease in another thread on here someplace..
Heres a youtube describing how to use the grease and don't put it on the end of the sparkplug..

https://m.youtube.com/watch?v=-542IYGBbpg

(just in the spirit of US all learning from this web site)

thanks for sharing the web site plus I offer the following; Dielectric grease should also be applied to the actual contact as well, because the contact pressure is sufficient to penetrate the grease. Doing so on such high pressure contact surfaces between different metals has the advantage of sealing the contact area against electrolytes that often cause rapid galvanic corrosion

 

[pvan]

Die electric/insulating grease on the boot maybe but if you put any thing on the threads then how much you torque the spark plugs will change . The spec for dry torque on spark plugs for a Merc. 7.4 is 15 ft lb. / 20 Nm. according to Performance Product Technologies web site. If you use any thing on the treads then you can not use those specs. Why would you put an insulating compound on the out side of a spark plug threads that in suppose to be grounded to the head. Most die electric grease unless high temp is not rated for the heat it will see at the spark plug threads. Most good quality spark plug threads are treated so you do not need to put any thing on them. If you use the wrong compound at those temperatures it will harden and act like lock tight.

Dielectric grease is a silicone based gel that in my opinion is fine for the spark plug threads due to it helps get the plug stared into an often rusty hole and does not effect torque.

 

[Air O'Nautical]

Sorry CSR, didn't want to turn this into pissing contest.
Do what every your comfortable with...

Has anyone ever (really) use a torque wrench on a spark plug? Some things require the correct torque but, other things require the correct person on the other end if the tool..

 

[dvx216]

At 15 ft lbs by spec is not much most spark plugs are over torqued without a torque wrench. Over torquing may cause galled threads because of the cast head and harder spark plug threads. I have never been able to gauge how much torque I was applying to a fastener be it a 3/8" bolt or a 4" turbine shell stud unless I used a torque wrench of some kind. Is it worth the risk to over torque one spark plug to find out the next time you change plugs that you have galled a head.

 

[pvan]

Sorry CSR, didn't want to turn this into pissing contest.
Do what every your comfortable with...


Not sure how sharing factual based info intended to help owners... qualifies as pissing so just take your own advice

 

[Air O'Nautical]

Sorry CSR, didn't want to turn this into pissing contest.
Do what every your comfortable with...


Not sure how sharing factual based info intended to help owners... qualifies as pissing so just take your own advice

Geese...Easy does it Pman...

I'm not suggesting your wrong.
Applying to the tip is acceptable practice, as long as you have a good hard snap on plug boot to over come the insulation of the grease.

This was hashed out a while ago and many aren't comfortable putting a nonconductive grease on the tip and only put it on the inside of the boot...also, an acceptable practice.

Stay calm and boat on...

 

[Boater420]

I finally had time to change the spark plugs on my 454's with V-drives. It took less than 3 hours to change the wires and plugs with a helper. I'm 6' foot 3" and weigh 190 lbs so it wasn't real easy moving around in the engine compartment but I never got stuck and was able to reach everything. I suggest anyone doing this job have a cell phone on your person or a helper in case you get stuck. Having a helper also makes it easier and the job go faster.

I did the job in three sections:

1. Climbed over the port engine and stood by the belts. From there I was able to change out the 4 outboard plugs. Standing in the same spot I then changed the inboard plug closest to the stern on the port and then the same plug on the starboard engine. It was easiest reaching these 2 plugs from this location.

2. I then moved to the spot between the V-drives and kind of slumped down until I was almost sitting. It's a little tight in this area but I was able to reach the remaining 6 inboard plugs from here. Once finished from this position I was had completed the port engine and the inboard bank of the starboard engine.

3. I then climbed over the starboard engine and stood by the belts and replaced the remaining 4 plugs on the starboard engine.

Tools required:
3/8" Drive Ratchet, 5/8" spark plug socket w/rubber insert to hold the plug in place, 3" & 6" extensions and one swivel.
Spark Plug Boot puller
Plug Gap Tool
Flashlight
Telescopic magnet to retrieve lost tools
Shop Towels

As suggested I only did one plug/wire at a time to avoid confusion. Move slowly when replacing the plugs so one doesn't get dropped in the bilge. I didn't use the Die electric/insulating grease and hand tightened the plugs.

View attachment 44093

 

[kap2]

When you say "hand tightened the plugs" do you mean you use a ratchet and not a torque wrench?

 

[Boater420]

Yes, tightened with ratchet only, no torque wrench.