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RedDog
09-24-2009, 08:22 PM
The spark plug question prompts this -

my '98 502 MFI has never had the distributer cap or plug wires changed. Likely around 260 - 300 hours on them.

should I change them? Anything else that should be addressed?

BlownCrewCab
09-24-2009, 09:13 PM
Although it's not like a tune up of old, as time goes on the parts still wear to some extent. Wires become more resistant, Plug Gap becomes Larger from wear as does the Gap of the Rotor button to distributer cap. it all wears at such a slow rate that you cant really tell. If you do a "Tune Up" of Wires, Cap, Button, Plugs, Etc you'll probably be able to tell from throttle response or even fuel milage. Certainly Can't Hurt, and Is probably $100 or less. I Vote to do it:yes:

The Hedgehog
09-25-2009, 07:18 AM
The spark plug question prompts this -
my '98 502 MFI has never had the distributer cap or plug wires changed. Likely around 260 - 300 hours on them.
should I change them? Anything else that should be addressed?

I benefitted from changing mine on my '97 502 mag years ago. The engine had around 250 hours on it when I did it and I got the results that Blown Crew cab was talking about. Nothing earth shattering but it did run a good bit better.

BigGrizzly
09-25-2009, 09:49 AM
+1 on this. Just a note the rotor gets shorter the longer it is run. This was a old emissions thing with short rotors in autos the old chevy guys should remember this.

RedDog
09-25-2009, 11:22 AM
Thanks all - I'll replace the wires, distributor cap, rotor, and plugs as soon as I round them up.

Dr. David Fleming
09-29-2009, 07:16 PM
When I was a mechanic at the Chrysler dealer back in the 70's we did all that tune-up parts replacement to make money. My personal experience shows that a lot of this was really not necessary. My fairly new Chrysler 300 for example has 275,000 miles on the original wires, cap, rotor etc. I would think that 425 hours on a Merc would hardly compare to this.

Sparkplug replacement on old leaded fuel engines was every 10,000 miles because of the lead fuel. Unleaded engines often run 100,000 miles on plugs and the cap, rotor, ignition wires are usually replaced only when they fail.

Boat breakdown, however, is nowhere near as convenient as a car breakdown. I assume this is why the Merc Racing 525 has redundant ignition systems as does the Merc 496 - these engines have separate igniton for each cylinder - ignition timing is by crank trigger or distributor insert that functions as a trigger.

Another issue to consider is the quality of OEM parts compared to replacements. I have seen better quality on the assembly line parts than what you get from the parts department. This has given rise to the saying "if it aint broke don't fix it."

Send me your cap and wires and I will reuse them.

Dr. d

The Hedgehog
09-29-2009, 08:34 PM
When I was a mechanic at the Chrysler dealer back in the 70's we did all that tune-up parts replacement to make money. My personal experience shows that a lot of this was really not necessary. My fairly new Chrysler 300 for example has 275,000 miles on the original wires, cap, rotor etc. I would think that 425 hours on a Merc would hardly compare to this.

Sparkplug replacement on old leaded fuel engines was every 10,000 miles because of the lead fuel. Unleaded engines often run 100,000 miles on plugs and the cap, rotor, ignition wires are usually replaced only when they fail.

Boat breakdown, however, is nowhere near as convenient as a car breakdown. I assume this is why the Merc Racing 525 has redundant ignition systems as does the Merc 496 - these engines have separate igniton for each cylinder - ignition timing is by crank trigger or distributor insert that functions as a trigger.

Another issue to consider is the quality of OEM parts compared to replacements. I have seen better quality on the assembly line parts than what you get from the parts department. This has given rise to the saying "if it aint broke don't fix it."

Send me your cap and wires and I will reuse them.

Dr. d

Go for it man.

Have you put 425 hours on a Merc? I have, and then some. It is not the heat in the marine environment that is tough.

What I DO know is that I have seen the results the Blown Crew cab is mentioning first hand. That is coming from a guy that once said "it is not really that hot in a boat engine compartment so that can't happen."

These are not car engines.

Dr. David Fleming
09-29-2009, 08:53 PM
Yah I know - "ain't broke don't fix it" - is hard for gyros to understand,

Trying to learn from the masters, I've been hanging around Tyler Crockett racing engines for a couple of years and I have yet to see these guys get into the wires, cap, rotor. I've seen them replace blown pistons, crankshafts, bent valves shot rocker arms and then put the engine right back together for another race without doing the wires, cap, and rotor on any engine.

I begged these guys to do this when they did the 502 racing cylinder heads and Crane rockers on my 22ZX - still I got back the original stuff and one wire had a split boot on the spark plug - and the thing just runs...runs...runs.

Like I said send me the cap and wires.

Dr. d

Pismo
09-30-2009, 05:56 AM
Time is what kills in those setups. My 96 fresh water only 502 Mag had only 150 hours on it when I looked under the cap. You won't believe how rusted and corroded everything was in the distributor. It isn't a Thunderbolt system, it is a stock GM system and they must be very poorly ventilated. I ended up replacing the whole distributor.

MOP
09-30-2009, 07:26 AM
Until the day that God commissions you to walk on Water do proper maintenance.

Pismo
09-30-2009, 07:53 AM
Until the day that God commissions you to walk on Water do proper maintenance.

"Proper" is the vague random element in that statement. 75% of what the merc manual or your dealer tells you to do in un-necessary. In cars it is even worse, more like 95%. A good car, for instance, can go 100,000 miles with nothing but oil and filter changes but your dealer will certainly tell you otherwi$$$e. Boats too can go a long time before they need much done, like the drive removed and serviced for example but lots of dealers will tell you to do it every year which is un-necessary but very costly...

Ghost
09-30-2009, 08:18 AM
"Proper" is the vague random element in that statement. 75% of what the merc manual or your dealer tells you to do in un-necessary. In cars it is even worse, more like 95%. A good car, for instance, can go 100,000 miles with nothing but oil and filter changes but your dealer will certainly tell you otherwi$$$e. Boats too can go a long time before they need much done, like the drive removed and serviced for example but lots of dealers will tell you to do it every year which is un-necessary but very costly...

My 7.4GiDP only gave me a couple of unenthusiastic starts before the distributor cap and rotor rendered it non-operational. All the bolts in the drive seemed like they needed the annual pulling, thread cleaning, and re-coating on reassembly. Plenty of white powder in the threads every year. And so on. Occasionally there was some water inside the boot. Etc, etc.

So, I wonder about the definition of "necessary" as a function of probability of breakdown, and also as being dependent on whether you live somewhere that annual winterization is needed, and whether you operate very sporadically, somewhat sporadically, etc. I think you are correct in that there are plenty of items in the maintenance lists that may have shorter spec maintenance intervals than needed for many people's probability of avoiding breakdown to be satisfied. At the same time, I wonder if that probability may be lower than it "should be" in the case of many people, and the spec may be written to keep you out of trouble if avoiding breakdown is critically important. Just a thought.

The Hedgehog
09-30-2009, 09:37 AM
Time is what kills in those setups. My 96 fresh water only 502 Mag had only 150 hours on it when I looked under the cap. You won't believe how rusted and corroded everything was in the distributor. It isn't a Thunderbolt system, it is a stock GM system and they must be very poorly ventilated. I ended up replacing the whole distributor.

Yep. It is just the way it is. Along with some of the factors that Ghost said. That probably makes it a case by case situation. For instance I can probably get away with twice as long on some things in my cruiser. It spends a good bit of time running at 2,000 - 3,000 RPM, gets run regularly in the winter and the engine compartment does not really get damp.

Pismo
09-30-2009, 09:43 AM
Salt vs Fresh(clean fresh that is) makes a huge difference as well. 10:1 maintenance.

chappy
09-30-2009, 02:20 PM
Like I said send me the cap and wires.

Post an addy.

I'll prep the pallet(s).

We'll think of it as a High Performance Boating Engine Parts recycling program.

Now, we're all green.:shades:

MOP
09-30-2009, 09:11 PM
Salt vs Fresh(clean fresh that is) makes a huge difference as well. 10:1 maintenance.

I having been a salt water mechanic longer then some are old on this board would love to know where you the 10:1 figure, proper initial prep alleviates most all of the salt water issues. The main complaint in salt is corrosion, granted with no maintenance you will have corrosion. My boat lives in salt it has little no corrosion, all it takes is a little care. Fresh water is better no question, but another point about fresh water is the structural wood in the fresh water boats rots way faster then in salt. This is a well know fact backed by any and all wooden boat restorers, salt tends to protect the wood. The tale is is if it come from a lake it needs a bottom, if it comes from salt it needs clean up and the chrome redone. Old timers would dump bags of rock salt in the bilges to save the bottoms, I have been on the wrong end of this bisiness for way to many years to agree with the fresh water rhetoric that is spewed so much! Most of it comes from those that don't either boat in it or don't not take care of their boats!

Dr. David Fleming
09-30-2009, 11:20 PM
This fresh water rot issue depends where you boat in the fresh water. Take for instance the 18th century warship on the bottom of Lake Ontario in the great lakes. It was sunk in the war of 1812 and found by J. Cousteau and featured on National Geographic. For C.... sakes the dead sailors are still on the thing. In Lake Superior the wreck of the Kamloops a steamer that went down at the end of the 19th century (1890's) scuba divers regularly encounter an engineman floating in the engine room. He was fixing the damn steam engine when the boat capsized "Lake Superior never gives up her dead." Wood boats from these lake are the most pristine in condition as there are no organic organisms in the fresh water to rot the wood. Not only that but the boating season is only 1 or 2 months long so the wood, engines etc hardly get used. Sunny days are sometimes not included in the average summer. So fresh water from some Florida swamp is a lot different than fresh water elsewhere.

Another example is the mahogany racing boat LIBERTY which had a state of the art stolen from the military World War I - 8 cyl aircraft engine - it flipped and sank in a race in Pennsylvania in the 1920's the boat was upside down on the lake and could not be found. Five or six years ago it was located with modern sonar which spotted the rudder and was raised by salvors that spent years looking. The engine was sealed in the mud and still operational with minor repairs. It is in a museum now on the shore of the lake, as it was taken by the community from the salvors in a legal battle like old Mel Gibson and the Senor De Atochia (sp) the Key West gold galleon. Many are the yachts and speedboats on the bottom in the Great Lakes - home of the best scuba wreck diving - man the stuff down there is all museum quality.

My 22ZX came from northern Michigan - in a time capsule! I try not to abuse it.

Dr. d

BigGrizzly
10-01-2009, 06:17 AM
Gees, all hw wanted to know weather heshould change the plugs, did not caes about anything else. Since boating is short changemthen every year just good insurance. If you can' afford this get a row boat

Pismo
10-01-2009, 06:32 AM
I having been a salt water mechanic longer then some are old on this board would love to know where you the 10:1 figure, proper initial prep alleviates most all of the salt water issues. The main complaint in salt is corrosion, granted with no maintenance you will have corrosion. My boat lives in salt it has little no corrosion, all it takes is a little care. Fresh water is better no question, but another point about fresh water is the structural wood in the fresh water boats rots way faster then in salt. This is a well know fact backed by any and all wooden boat restorers, salt tends to protect the wood. The tale is is if it come from a lake it needs a bottom, if it comes from salt it needs clean up and the chrome redone. Old timers would dump bags of rock salt in the bilges to save the bottoms, I have been on the wrong end of this bisiness for way to many years to agree with the fresh water rhetoric that is spewed so much! Most of it comes from those that don't either boat in it or don't not take care of their boats!


Ok, 7.128:1. Lots of 50+ year old boats on fresh lakes with original everything, manifolds, drive rigging, etc. How many years do you get out of stock iron exhaust manifolds in salt, 5, maybe. Salt is brutal. It eats up so much. I will agree that wood does better in salt tho. Those dry rot bugs live better in fresh water. My outboard whaler lives in both salt and fresh and one summer in the salt causes more damage than 10 or more years in fresh easily. Pitting, corrosion, etc. It's all the salt.

jimishooch
10-01-2009, 08:37 AM
Thanks all - I'll replace the wires, distributor cap, rotor, and plugs as soon as I round them up.

check the timing after you put in all the new stuff.
jim

RedDog
10-01-2009, 08:50 AM
check the timing after you put in all the new stuff.
jim

Is that necessary? Isn't timing on a '98 502 MPI controlled by the ECM? Wish I could find my missing service manual...

The Hedgehog
10-01-2009, 09:02 AM
Is that necessary? Isn't timing on a '98 502 MPI controlled by the ECM? Wish I could find my missing service manual...

Absolutely! While you are at, I would pull the engine and check the stringers. They may be rotting away since you are not in salt water. Come to think of it, your whole boat is probably screwed! I am getting a large hypoberic (sp?) chamber for storing my boats. I read that is the only proper way to preserve them.

FYI, I did not fool with the timing when I gave my 502 Mag a simple tune up. Like I said, it was happier in the end.

A2VeeDub
10-01-2009, 02:21 PM
This fresh water rot issue depends where you boat in the fresh water. Take for instance the 18th century warship on the bottom of Lake Ontario in the great lakes. It was sunk in the war of 1812 and found by J. Cousteau and featured on National Geographic. For C.... sakes the dead sailors are still on the thing. In Lake Superior the wreck of the Kamloops a steamer that went down at the end of the 19th century (1890's) scuba divers regularly encounter an engineman floating in the engine room. He was fixing the damn steam engine when the boat capsized "Lake Superior never gives up her dead." Wood boats from these lake are the most pristine in condition as there are no organic organisms in the fresh water to rot the wood. Not only that but the boating season is only 1 or 2 months long so the wood, engines etc hardly get used. Sunny days are sometimes not included in the average summer. So fresh water from some Florida swamp is a lot different than fresh water elsewhere.

Another example is the mahogany racing boat LIBERTY which had a state of the art stolen from the military World War I - 8 cyl aircraft engine - it flipped and sank in a race in Pennsylvania in the 1920's the boat was upside down on the lake and could not be found. Five or six years ago it was located with modern sonar which spotted the rudder and was raised by salvors that spent years looking. The engine was sealed in the mud and still operational with minor repairs. It is in a museum now on the shore of the lake, as it was taken by the community from the salvors in a legal battle like old Mel Gibson and the Senor De Atochia (sp) the Key West gold galleon. Many are the yachts and speedboats on the bottom in the Great Lakes - home of the best scuba wreck diving - man the stuff down there is all museum quality.

My 22ZX came from northern Michigan - in a time capsule! I try not to abuse it.

Dr. d


Most of the wood on the Great Lakes wrecks stay together because of the low water temperatures at the bottom.

The Hedgehog
10-01-2009, 03:27 PM
Most of the wood on the Great Lakes wrecks stay together because of the low water temperatures at the bottom.

Yep. Wood won't really rot if you keep it all the way wet. That is why posts on docks that are below the water line do fine and wood above the waterline will rot. That even happens in Alabama.

Donzi Vol
10-02-2009, 05:00 PM
The spark plug question prompts this -

my '98 502 MFI has never had the distributer cap or plug wires changed. Likely around 260 - 300 hours on them.

should I change them? Anything else that should be addressed?


Although it's not like a tune up of old, as time goes on the parts still wear to some extent. Wires become more resistant, Plug Gap becomes Larger from wear as does the Gap of the Rotor button to distributer cap. it all wears at such a slow rate that you cant really tell. If you do a "Tune Up" of Wires, Cap, Button, Plugs, Etc you'll probably be able to tell from throttle response or even fuel milage. Certainly Can't Hurt, and Is probably $100 or less. I Vote to do it:yes:

Go for it, Tim. If I can do it, anybody can! Of course I did have the oversight of my boy Mike. Either way, takes an hour and $100 to keep her running as well as she looks (sounds like some girls I've dated...haha).

joseph m. hahnl
10-02-2009, 05:43 PM
Yah I know - "ain't broke don't fix it" - is hard for gyros to understand,

Trying to learn from the masters, I've been hanging around Tyler Crockett racing engines for a couple of years and I have yet to see these guys get into the wires, cap, rotor. I've seen them replace blown pistons, crankshafts, bent valves shot rocker arms and then put the engine right back together for another race without doing the wires, cap, and rotor on any engine.

I begged these guys to do this when they did the 502 racing cylinder heads and Crane rockers on my 22ZX - still I got back the original stuff and one wire had a split boot on the spark plug - and the thing just runs...runs...runs.

Like I said send me the cap and wires.

Dr. d


With modern solid state ignitions bad wires and boots will short the coil pack.If the Resistance in the wire is off at all it becomes more than just replacing wires.

Older pointless ignitions are much more forgiving and like said will run and run. But for optimum efficiency and performance they should be replaced
some what regularly.

RedDog
10-05-2009, 07:22 PM
Got the new wires, plugs, cap and rotor installed. There was a lot of corrosion inside the cap and the rotor was wore down quite a bit. The old wires didn't look so good. The plugs looked fine but I had replaced them about 120 hours back.

I went with Mallory Marine wires, cap and rotor. Much cheaper than the Mercruiser stuff and hopefully better quality. Plugs were AC-Delco R43TS.

BlownCrewCab
10-05-2009, 07:43 PM
The Mallory stuff is just as good, and with all the Idleing you do(where's the smiley of a boat towing a boat) :yes: It'll help your motor run Tops when you do decide to get on it .

The Hedgehog
10-06-2009, 06:41 AM
You know, we are on a well in Michigan with a water softener. I am on the way back up there tomorrow, so I could grab a couple of the Morton's 40 pound salt bags I keep around for the well water treatment and throw them in the bilge of the Donzi over the winter lay up. Bill, do you think I should grab the green bags with the rust treatment additive, just to be safe?
And to think, I just got everything put back together. Hate to miss this all important step to keep my stringers from rotting....

I think that you are pretty much screwed at this point. It is a good bit more complicated than that. It is a combination of temp, salinity and pressure. One wrong move in any direction and your stringers may actually turn into oil. How do you think that we got all of that oil in both the ancient bogs that were in the gulf off Louisiana and Alaska? It you get it right though, they will last for thousands of years. Just last night I saw how they recovered some ancient Greek Ships in the Med. They got lucky with the pressure/temp combo, but we could learn a lot from them. At this point your best bet would be to remove the wood from your stringers and pressure soak them in tar. Then reinstall. Anything less and you are simply running on borrowed time.:shocking:

No I am not an expert on the matter but I actually am in a Holiday Inn Express right now and saw some History Channel last night. I think that makes me pretty qualified.

Now if only I can figure out how to actually FEEL smarter when in a Holiday Inn Express! I feel pretty smart when I am out having dinner and drinks to compensate for being on the road, but then I don't actually feel smarter the next day.

CHACHI
10-06-2009, 07:26 AM
You know, we are on a well in Michigan with a water softener. I am on the way back up there tomorrow, so I could grab a couple of the Morton's 40 pound salt bags I keep around for the well water treatment and throw them in the bilge of the Donzi over the winter lay up. Bill, do you think I should grab the green bags with the rust treatment additive, just to be safe?

And to think, I just got everything put back together. Hate to miss this all important step to keep my stringers from rotting....

Maybe Mr. Carter could come thru with a "group buy" price.

Ken

MDonziM
10-06-2009, 08:07 AM
Got the new wires, plugs, cap and rotor installed. There was a lot of corrosion inside the cap and the rotor was wore down quite a bit. The old wires didn't look so good. The plugs looked fine but I had replaced them about 120 hours back.

I went with Mallory Marine wires, cap and rotor. Much cheaper than the Mercruiser stuff and hopefully better quality. Plugs were AC-Delco R43TS.

I run in salt water but my boat is never in the water more than 5 hrs. I had a 502mpi in my 22 and I changed the plugs ,dist cap and rotor every year. (maby 60 hrs of use) Don't know Mallory caps but MSD get real dirty real fast. Looked at mine the other day w/ 40hrs on it and I would have guessed it was 2-3 yrs old.