Spark Plugs and engine timing

[Lucky Penny]

First question first (a good place to start.) I have a 1977 Mercruiser 5.7L and the books (all that I have read,) state that the proper spark plug for this engine is R43T. I have heard from 'shade tree mech's" that I can improve the proformance (efficency) if I switch to R43TS I know that my pistons are flat, but before I stick anything into the cyl, I want to make sure that there is enough clearance. I do not need the greef of smacking the piston heads against anything other then air/fuel mixture.
Question: is it safe to use the extended tip plugs? And would it really help with efficency? I have a small crusier, not a speed boat.

Second (follows first,) I have recently installed an electronic ign system, and completely eleminated the points and condenser. I was told by several mech's that I should change my timing from 10BTDC to 8BTDC is this also good information?

Thanks for any constructive input

 

[Don S]

Re: Spark Plugs and engine timing

The S on the end of the spark plug number stands for "Extended tip". While that might work for a car, it's not the same in a marine engine But with your stock Mercruiser engine, stick with the stock plugs for best burn. Merc does a lot of testing and changes plugs on engines quite often. But the havent on yours.
You say you installed an electronic ign system, but you didn't say what kind. IF just a Pertronix upgrade, stick with the OEM recommended timing. The advance system is still the same and has more to do with idle timing than rather it's electronic or points.

 

[Lucky Penny]

Re: Spark Plugs and engine timing

Thank you for the reply. The ign upgrade was Molery (sp) and I will stick with the R43T. I just didn't feel comfortable poking anything down into the cyl and take the chance of ruining the pistons.

 

[Mkos1980]

Re: Spark Plugs and engine timing

I started to run the CR43TS's No problems whatsoever. We did a little dyno testing when the motor was out and picked up 5HP with the extended tip plugs.

 

[TollyWally]

Re: Spark Plugs and engine timing

Mkos,
That's interesting, do you have any power curves you couled share with us?

 

[Scaaty]

Re: Spark Plugs and engine timing

I started to run the CR43TS's No problems whatsoever. We did a little dyno testing when the motor was out and picked up 5HP with the extended tip plugs.

So ya pulled the motor for some odd motor Dyno testing?...we are probably talking a 350 GM here...right? What did you get that extra "5" at??? Probably not the normal in a boat 3500 R's, more or less.
43 T's (AC)...been in there for decades...work fine, have for years. Its the camshaft, and in/out/ air/fuel..and good ignition...ya want the "torque"..where needed...
Yeah..dump the timing to 8 degrees...(10 to high anyway..crap gas nowadays...I run my 5000 pound 25foot barge at 7 1/2..planes at at 3000 fine...on the new electronic...

 

[bruceb58]

Re: Spark Plugs and engine timing

The only reason you would want to change the timing at idle is if the electronic ignition somehow effects the total advance at high RPM when the distributor is putting in its full advance.

 

[Mkos1980]

Re: Spark Plugs and engine timing

We started off with regular 1990 260HP 5.7 Alpha one. We pulled motor to do some testing and to add a camshaft. Heres a link to my other post.

http://www.speedwake.com/upload/showthread.php?s=&threadid=52583

 

[Mkos1980]

Re: Spark Plugs and engine timing

Before the dyno runs I had my motor with just the highrise intake and the timing locked at 34* with a 22 module. Was running about 12* initial. Never had a problem with pinging or anything with 87 octane. The boat nicely responded by picking up 150 rpms. But then again my boat is alot lighter then your "barge" scaaty. For a heavier boat I would run less timing.

 

[TollyWally]

Re: Spark Plugs and engine timing

Mkos,
How sweet to have a dyno on demand! I am interested in your MSD ignition set up. How much $, are the ignition curves programable? If so, programable on the fly?

Access to a free dyno, priceless

 

[Mkos1980]

Re: Spark Plugs and engine timing

Tolly, The MSD setup was a regular non marine one we used for purpose testing only. (Pro Billet and a 6A box) I am still using the TB IV setup with a 22A module and 12* timing in the boat. Both give me the 34 I need.. The timing cruves can be changed on a MSD setup if you prefer to go that route. The can also be changed on the TB IV setup as well by changing the ignition module. There is a 22 22A 24 and 24A module (Probbely a few less common ones as well.) Not cheap though They are not on the fly. MSD does make a blue series dis and ignition box to be USCG safe as well.

 

[Mkos1980]

Re: Spark Plugs and engine timing

I am trying to get a 24 module as this will help me lower my initial to 10 and be a little safer during the low and mid rpm range with more people and gear.

 

[Scaaty]

Re: Spark Plugs and engine timing

Before the dyno runs I had my motor with just the highrise intake and the timing locked at 34* with a 22 module. Was running about 12* initial. Never had a problem with pinging or anything with 87 octane. The boat nicely responded by picking up 150 rpms. But then again my boat is alot lighter then your "barge" scaaty. For a heavier boat I would run less timing.

You are getting off the original posters subject. He did not ask for some race motor info.."K"? (like we all run "High Rise Mans"?
And I have 50 years wet...still at 4 boats, 8 motorcycles (48 years saddle time..retired at 44, so I aint stupid either..hitting 58 soon) ..wrenched, and a Machinist all my life..and kinda know my way around anything that floats..or will hug a corner on sticky Radials..2 wheel wise..HD's and Honda Sportbikes...way too much "rear wheel HP"
And my "barge"...(350 GM...5000 pounds...24 foot)...is one of many...still have the 20 footer, 125OB, and my 15 foot Flatbottom Dragboat..with a crank up rebuild "Tower of Power"...blows Jetskis off on a "NAIL IT".
We try to help here on IBoats...but ya gotta stick too the original posters question...not what you might have done...(which sounds cool by the way..but has zip to do with the posters question...
Nuff out of me..just a "venting"...
(and I just did an Electronic on the 350.."barge"..(orig points)...and like Don said..."helps to know just what was involved..."Pertronix", or full system...(its the little things)...
And I can't close without the "Split Fire" Plug "junk".."More horsepower..better mileage"..BS..yeah ..right..got there butt sued off for "false advertizijng"
MSD the best though..no prob there. ."Multible Spark Discharge"..(also too much time NHRA too...Have a Harley Dragbike).....

 

[TollyWally]

Re: Spark Plugs and engine timing

Mkos,
Thanks for the info about the ignition set up. I am under the impression that many if not most electronic ignitions with modules etc. are basically "sparkless", that there is not an open flash like a points style ignition
that might cause mischief in a spilt gas in the bilge scenario. I have also thought that one major difference between automotive and marine distributors was having a vacuum advance in addition to the mechanical advance. I sure would like infinite on the fly adjustment. LOL, I would also like access to a private dyno!

 

[Mkos1980]

Re: Spark Plugs and engine timing

Scaaty. The highrise is stock production on all 87-95 MerCruiser 350 Magnums. The cam I chose is stock on Mercruisers newer 377 or 383 Crate motor. Only reason I posted this was the guy seemed a little performance oriented.

 

[Don S]

Re: Spark Plugs and engine timing

I am under the impression that many if not most electronic ignitions with modules etc. are basically "sparkless", that there is not an open flash like a points style ignition

That only eliminates the spark from the points. How do you think the spark gets from the rotor to the distributor cap?? Trust me, it arcs across. The rotor never contacts the outer contacts of the cap.

LOTS of Sparking going on

 

[Lucky Penny]

Re: Spark Plugs and engine timing

FOR DON S.
OK, I cleaned the Distr cap contacts and rotor. replaced a plug with a crack, set the timing to 8BTDC rest set idle (in gear) to 650RPM, adj the idle screws to obtain a steady vac of 18" reset idle speed to 650RPM. plugs were inspected. cleaned, and confirmed the gap at .035"

Engine is running rock steady. the only thing I did notice was greyish bubbles in the water at idle not in gear. no smoke or film on the water.

Did I miss anything.

 

[Don S]

Re: Spark Plugs and engine timing

Idle is not the best place to run for any engine. Did you adjust the idle mixture? That is part of the tuneup process. In my opinion, if a cap and rotor needs to be cleaned, then it needs to be replaced.

 

[Lucky Penny]

Re: Spark Plugs and engine timing

I adj the idle using a tach and vac gauge. I get the highest vac reading with the idle adjustment at about 1 3/4 turns on each side. as for the cap and rotor, there was no indication of burning or tracking.

I am still trying to figure out what the bubbles are, could it be carbon? I don't know....all I do know is it is not gas or oil (no film of any sort on the water)

engine runs great right now, oil pressure right where it should be, she is quiet, and very little if any vib, temp is dead on.

Like I said, she is just a small cruiser, I am not looking to break any speed records, just be able to afford to take my granddaughter out for a swim or a few bud's out for a days fishing and fun. And the way fuel cost is going nuts, be able to afford to do both.