Spark Plug keeps changing gap??

[mblaney]

I also recommend Seafoam; my '75 Merc Thunderbolt 500 was stored for a long time (before I got it) and it did not run very good. I gave it the Seafoam treatment and now it runs too good (I am not a merc man but I can't find anything wrong with this one!)

Without brand bashing, I suggest using the Champion plugs.

If you suspect that your motor is running hot, have you checked for cooling? That engine should have a very steady water flow out the tattle-tale, even at idle.

I had a '69 Sportwin 9.5 and that was an awesome motor. Wished I could have it back.

[plncrzy]

HI Chen,

Your motor takes

Champion J4J Spark Plugs as stock This number also converts to a
NGK B7S. Those are the plugs you need, you do not want any other letters or numbers in the plug description. Any Benson Auto Parts will be able to get THOSE plugs for you if not let me know.

Loosing power when hot could be a number of things like ignition breaking down, Fuel Starvation and more but the right plugs are good place to start. Those motors have minimal compression to start with so making them work harder with the wrong plugs is not a good thing.

regards,

Dave

Funny how different web sites state different plugs... although very close.. I see some ask for a NGK B8S and some for a champion J4C... but if these were taken out of a book, then I would go with Daves #'s

[mblaney]

I think the confusion is due to the HP? The plugs are basically the same.

For '64 - 73 9.5 hp the plug is J4C
For > '58 10 HP (not 9.9) and some others (5.5, 6, 7.5) use J6C

From Champions web site:
J4C: 14mm Thread Size, 9.5mm (3/8") Reach, 13/16" (20.6mm) Hex Size, Gasket Seat, Non-Resistor, Copper Core, Heat Range 4

J6C: 14mm Thread Size, 9.5mm (3/8") Reach, 13/16" (20.6mm) Hex Size, Gasket Seat, Non-Resistor, Copper Core, Heat Range 6

If I remember correctly I think I used J4C in mine.

[Doeun_k]

hey hawkers,

yeah i went in to buy some and they said they changed the J4J to the J4C, they said it is the exact same but just different name, went with champion i only use ngk plugs in a japanese car like my honda hehehe......thanks for the input .......Im going to buy some seafoam tommrow and do a smoke show at my friends cottage and also to test run the plugs.

thansks hawkers for pointing me to the right direction

Chen K

[FishToLive]

Give us an update on your seafoam results....

[Doeun_k]

hey craig,

just to make sure before i do my seafoam treatment, do i add the whole can to 3/4 gallon of gas ????and don't forget the oil too..........

or do i just add a couple of oz.????

Chen K

[cprince]

hey craig,

just to make sure before i do my seafoam treatment, do i add the whole can to 3/4 gallon of gas ????and don't forget the oil too..........

or do i just add a couple of oz.????

Chen K

3/4 gal gas
16oz Seafoam
3oz of oil

Mix then run through the engine.

Where did you get your seafoam? I bought mine when I was in The States last year because I couldn't find any in my area.

Craig

[MLR]

NAPA sells seafoam

[GR8-Scott]

NAPA sells seafoam

Beat me to the punch....

[Doeun_k]

correct napa i got mine off industrial it is about $11 there

Chen K

[crankbearing]

Yep, Forgot to mention that j4 changeover, Be careful that seafoam does not heat up the motor too much. I use Tohatsu engine tuner (It is sprayed into the carb venturi for a whole can then shut the motor off and let it sit for 10-15 minutes then start and burn it off) on anything more than 10 years old. If motors do not idle for extended periods of time there is no reason to treat them at all - if you use GOOD oil there should be not carbon build up on the ring lands carbon on the exahust side of a piston dome is NORMAL as long as it is brown and not black. Good Tune Ups, Tight point gap, good coils and condensers with a steel on steel needle and seat and you are golden, oh and make sure your old carb floats are not saturated or porous and if your primer bulb is hard your fuel line is JUNK too - Guaranteed.

Ethanol is WAY harder on todays motors... Spark plugs are brand choice, I run NGK and Champion in my racing 44XS mercs and depending on climate I will change from NGK to Champion in certain conditions on a 30 degree day in the shade I can foul an NGK real easy, but the champions run fine but these are racing plugs fine wire - NON RESISTOR. I run 12-16:1 Klotz Oil in my engines which is 20% degummed castor.

I notice someone mentioned a 50 Merc, 50 Mercs were terrible for prolonged periods of low speed running, The old designed inner exhaust divider would allow carbon to build and build, until finally it would break off and enter the cylinder through the port windows and collapse the rings on the exhaust side or push the exhaust cover out and cause an internal water leak.

Regards,

[cprince]

@crankbearing

Love what you have to say! Great advice!!!

I am not familiar with the Tohatsu brand of carb cleaner. You say that it is a spray into the throat type treatment... I was told by more than a few not to do that. On smaller motors, they seem to think that it impacts the carb diaphragms and gaskets in a negative way. What say you?

Most people don't use "Good" oil. I have been guilty of it on a few occasions. What do you recommend for oil?

Thanks for all your input... I might pick your brain about my old 'Rudes soon enough!

Craig

[crankbearing]

Craig,

Yep that can be true in some instances that is why there is a warning on the can to keep the motor under 1300 RPM. The one thing that the Tohatsu tuner does not have in it is the chemical that most spray carb cleaners have this is not a carb cleaner - forget that name right now - sorry, It is the chemical that turns aluminium white when you spray it and that is the one that eats your diaphragms.

Most motors other than Merc from 1975 to 1985 have a separate fuel pump and you are past the pump when spraying into the carb throat anyhow.

I tell ya it is a miracle in a can sometimes, I had an in-line merc I had re-built in the fall and it sat in a stand all winter, put it on the boat last weekend and ran it, It seemed like an igntion miss and after testing ignition components I sprayed a can into the carbs let it sit 20 minutes and voila it ran like a top, a little dirt in #2 carb was the issue.

Oil- AAAHHH! do not get me started, Yep I use crap oil once in the life of my motors and that is in the first tank on a fresh motor break-in ONLY and that is only because it such crap that it allows the engine to seat the rings better without getting too technical the cross-hatch in a bore is hills and valleys and on a new motor they are higher than a worn motor; bad oil allow the rings to break down those hills and valleys in a full circle and give you a good seal now imagine if you continue to use bad oil like CTC cheap stuff - The hills and valleys only last so long right that is when blow buy starts - good oils like Merc premium plus and BRP XP100 pre-mix is great stuff - The new Sierra Premium Plus Synthetic blend is very good and you can actually smell the difference when you add it, These are economical priced oils. Opti's should have Merc Premium Plus only. Stay away from Amsoil, red-line, Lucas etc,, I use Klotz for all my motors and it is awesome stuff the 20% de-gummed castor coats the internals of your motor and it is like new when you take them apart. I re-ring my race motors about every two years. All metal parts have a thin film of red on them but not thick as to slow inertia or rpm, just a thin protective layer that stays with the internal parts. I could go on and on.

But even worse today - Guys, GET a good water separating filter anykind as long as you have one, google ethanol and read some horror stories and you will get one real quick. Ethanol is bad stuff real bad, it eats Aluminium parts, It chemically reacts with fiber/plastic gas tanks if left sitting and the worst part is the actual amounts that are in fuels today are WAY higher than actually advertised on the pumps.

I void warranties on any motor I build if the customer does not have one installed and add STA-BIL to your tanks on every fill-up and more in the winter with a full fuel tank or better yet empty your tank on the last run of the year - so you have to fish an hour longer that day - LOL.

rgds,

Dave

[Doeun_k]

hey hawkers,

Seafoam did its job and i feel the power difference, i would use this again. I left it idleing and man there was alot of white smoke, I did it twice untill there was no smoke and it works wonderes.

thanks everyone for the help,

Chen K

[moonshine]

would seafoam work on 4 strokes as well? i have a 50 merc that suffers a bit when i give it throttle. sometimes it even stalls