Use of automotive parts on Mercruiser

[Knot Waiting]

Given the time Ive spent both working on my own boat and reading about boats on this forum I should probably know the answer to this.... but I feel more confident consulting a few communal experts first.

Is it ok to use automotive grade spark plug wires, rotor, and cap on a Mercruiser engine? Its a 1988 5.7 350. If I dont have to pay an unecessary premium Im not going to. Thank you.

 

[Bondo]

Re: Use of automotive parts on Mercruiser

Is it ok to use automotive grade spark plug wires, rotor, and cap on a Mercruiser engine?

Ayuh,... The sparkplug Wires,..?? The wires are the same wires, but the Ends won't be right....
The Cap,+ Rotor,..?? Chevy never used a Mercruiser distributer,.... They're Different....

Wanta save some money,..?? Click on the Mercruiser Parts links at the top of this page,....

 

[achris]

Re: Use of automotive parts on Mercruiser

Don't take this the wrong way, but why would you risk your life and the lives of your family to save $20? Parts are rated 'MARINE' for a very good reason.

I used to shake my head in disbelief when a customer would come into my shop looking for a 'cheap second hand outboard to use as an auxiliary'. When all else fails (main engine dead, no radio because the batteries died trying to start the main engine) they are going to be trusting their lives to a 'cheap second hand outboard'. Why die saving a few dollars?

Chris......

 

[backyard mechanic]

Re: Use of automotive parts on Mercruiser

As far as spark plug wires; auto wire is OK but remember the end material (often made of aluminum or copper/brass) should be similar to the cap material. The boot really doesn't make any difference as long as it covers the plug insulator and is spark proof.

As for distributor parts... If you can find internal automotive distributor parts that's OK but when you get to the cap you will find the automotive caps are cut out for vacuum advance or some have a "door' to adjust dwell angle. Both are places where fumes can leak into the cap and BOOM! That's why Bondo said the cap is going to be different.

Now all that said, the extra dollar spent to get marine parts is worth while. THIS is why...

 

[Don S]

Re: Use of automotive parts on Mercruiser

when you get to the cap you will find the automotive caps are cut out for vacuum advance or some have a "door' to adjust dwell angle.

Your name fits, I guess you haven't looked at an automotive distributor in about a ka-zillion years have you. Bondo proabably said what he did because Mercruser use the Thunderbolt ignition which was NEVER used on automotive engines. It's a marine thing ya know.

 

[JustJason]

Re: Use of automotive parts on Mercruiser

Distro Cap, Needs to be Marine Rated. But your not going to be able to go into an autozone and as for a cap that fits a GM350. The boat motors use a different distributor, and a different cap than an automotive equiv.

Rotor... Doesn't make a difference. But again, you can't go to an autoparts store and ask for a rotor that fits a 350, different distro, so it won't fit. Cap and rotors come as set's in nice little POS (point of sale) blister packs.

Plug wires. off the shel automotive wires are usually to short, plus they have the wrong ends on them. You don't want to have plug wires so tight they are riding on the exhaust manifols, your bound to melt one that way. The cap to coil wire has completely different ends, so it just wouldn't work. You can always buy one of those wire "kits" where you put your own "spring and needle" ends on and then get the rubber boots over them... but trust me its a PITA and not worth any kind of money savings. Especially if you cut a wire to short.

Spark plugs. The difference is in the alloy on the threads and the hex nut. Auto ones will rust in there pretty good. If you go to remove them after a season or two there's a good chance of you breaking the hex nut and leaving the threads inside of the head. Stick with AC Delco's marine rated MR43's

 

[Knot Waiting]

Re: Use of automotive parts on Mercruiser

Thanks for the input guys. I havent replaced the cap before so I didnt know it was a completely different design. Think the choice is pretty clear. Jason, I didnt know that about the plugs either, used NGKs from West Marine last year so hopefully they are built to marine spec. Oh, and had it not been for the 'point of sale' reference I would have assumed you liked plastic packaging as much as I do, lol.

 

[Gary H NC]

Re: Use of automotive parts on Mercruiser

Not much cheaper trying to rig auto wires...
Look at these for example...not expensive and good 8mm marine wires made for the Thunderbolt ignition..
Probably here on Iboats too...

http://bpi.ebasicpower.com/mm5/merc...BasicPower&Product_Code=MAL9-29350&NOSHOW=YES

 

[cr2k]

Re: Use of automotive parts on Mercruiser

NGK plugs rock! If you got them form West Marine they are the proper quality.

As far as using auto plugs, you could but you better load up the threads with anti-seize compound.

 

[mkast]

Re: Use of automotive parts on Mercruiser

As far as using auto plugs, you could but you better load up the threads with anti-seize compound.

Don't worry about grounding or heat conductivity.

 

[cr2k]

Re: Use of automotive parts on Mercruiser

The ground and heat go through the tapered seat.

 

[pac city]

Re: Use of automotive parts on Mercruiser

Don't worry about grounding or heat conductivity.

if you can find it, use the copper based thread lube from nkg,. don't need to put on thick, absolutly no prob with heat , or ground,?

 

[havasuboatman]

Re: Use of automotive parts on Mercruiser

Don't take this the wrong way, but why would you risk your life and the lives of your family to save $20? Parts are rated 'MARINE' for a very good reason.

I used to shake my head in disbelief when a customer would come into my shop looking for a 'cheap second hand outboard to use as an auxiliary'. When all else fails (main engine dead, no radio because the batteries died trying to start the main engine) they are going to be trusting their lives to a 'cheap second hand outboard'. Why die saving a few dollars?

Chris......

Boggles the mind, doesn't it? Everyone that buys a boat should be shown a video of an engine compartment explosion.

 

[mkast]

Re: Use of automotive parts on Mercruiser

The ground and heat go through the tapered seat.

If I remember correctly AC plugs aren't tapered, copper washer.

if you can find it, use the copper based thread lube from nkg,. don't need to put on thick, absolutly no prob with heat , or ground,?

Show me the Mercruiser maintenance manual this is stated in.

 

[pac city]

Re: Use of automotive parts on Mercruiser

If I remember correctly AC plugs aren't tapered, copper washer.



Show me the Mercruiser maintenance manual this is stated in.

show me how it hurts, and no benifites,. spun a few plugs over the years. do it ,or don't , don't care.

 

[mkast]

Re: Use of automotive parts on Mercruiser

show me how it hurts, don't care.

Sounds contradictory.

Used to teach a piston engine class in an A&P school.

From spark plug manufacturers
Use of anti seize on spark plugs will lead to:
Incorrect spark plug torque, up to 30%
Deteriorated ground path,
Increase in spark plug heat range due to decrease in heat conductivity.

That's at least three reasons why it's not in the Mercruiser maintenance manual.

 

[pac city]

Re: Use of automotive parts on Mercruiser

Sounds contradictory.

Used to teach a piston engine class in an A&P school.

From spark plug manufacturers
Use of anti seize on spark plugs will lead to:
Incorrect spark plug torque, up to 30%
Deteriorated ground path,
Increase in spark plug heat range due to decrease in heat conductivity.

That's at least three reasons why it's not in the Mercruiser maintenance manual.

then why would ngk offer a product for that purpose?

 

[Don S]

Re: Use of automotive parts on Mercruiser

I think both of you need to calm down, not only in this thread.

mkast - If I remember correctly AC plugs aren't tapered, copper washer.

Every spark plug maker makes both gasketed, tapered, and other types. The type seat depends on how the head was machined.

pac city - then why would ngk offer a product for that purpose?

If NGK actually does have a product for it, then post a link to it, don't just say they do.

mkast -
From spark plug manufacturers
Use of anti seize on spark plugs will lead to:
Incorrect spark plug torque, up to 30%
Deteriorated ground path,
Increase in spark plug heat range due to decrease in heat conductivit

Again, post a link don't just say they did.

If you guys are going to argue a point, at least post up some OEM proof, and I am not talking about something from some other forum. Proof from the OEM manufacturer.

 

[pac city]

Re: Use of automotive parts on Mercruiser

I think both of you need to calm down, not only in this thread.


Every spark plug maker makes both gasketed, tapered, and other types. The type seat depends on how the head was machined.



If NGK actually does have a product for it, then post a link to it, don't just say they do. will do. and will do.



Again, post a link don't just say they did.

If you guys are going to argue a point, at least post up some OEM proof, and I am not talking about something from some other forum. Proof from the OEM manufacturer.

will do. and will do.

 

[mkast]

Re: Use of automotive parts on Mercruiser

at least post up some OEM proof, and I am not talking about something from some other forum. Proof from the OEM manufacturer.

I have yet to see anti seize mentioned in the Mercruiser maintenance manual concerning spark plug installation.
I think Mercruiser is responsible for warranty on the product, OEM.
Here is the link:
http://forums.iboats.com/showthread.php?p=1693398#post 1693398