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Discussion Starter #1
So i know you can adjust your advance and that will affect your idle but higher in the RPM range what am i looking for in advance? Will a higher advance mean higher end RPM or is that not a concern?

I got it runnin ok I just dont know the ins and outs of advance and thought i would ask the pro's.

BTW, i think right now im set at 4 degrees before TDC at idle and once warm is around 1k. If i start getting below 1K it start idling rough. max RPM is currently right at 5K. Im not sure what advance it is at speed since my co-pilot is carrying my unborn child and is banned from the boat. Im hoping this weekend my buddy is gonna come out with me so i can check the advance. By getting info now i will be better prepaired for this weekend.
 

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Living in a cage of fear
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Well, I'm no pro, but I have screwed around a lot with advance settings.
In a jet boat, your "initial" advance is merely a by product of your total advance settings.
No one drives a jet boat at idle once you are off the trailer.
Many "lock" the advance mechanisms' completely out, so initial is set at the total advance wanted. (generally 35* in a BBC)
I PERSONALLY feel that it is easier starting, and less strain on starters, to use the mechanical advance in my distributor on my Miller.
However, I have "set" my distributor using the MSD spring and bushing kit to "dial in" only 14 degrees of mechanical advance, with the light springs having all of the advance in by 2200 RPM+-. (21* at idle)
What this means is that, basically, as soon as I start accelerating off idle (1000 RPM) it starts dialing it in and is almost immediately at full advance (2200-2400 RPM) It is in effect "nearly" locked out, but with a little mercy dialed in for starting.:D
I played with it extensively trying many different spring, weight, and bushing configurations, but always ending up at 35* total. Different ways of getting to 35* is what we are trying to maximize.
By using the adjustable, inductive timing light, we can record advance rates, total advance by mech., and vacuum means, and RPM that each stage happens at.

I would think that in a heavier boat, with less power, you may need a little more gradual, and longer, curve. (more like a car needs)
But the total will GENERALLY be the same.

I don't know if any of this makes sense, I just got back from having a couple of REAL GOOD margaritas!
 

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I like to set my motors up with 10-12 degrees initial advance for better idle and low end response. You need to know how much your distributor is advancing mechanically. I usually set up mech advance at 24 degrees, all in by 3000 RPM for a total of 34-36 degrees. ( 10-12 plus the 24) It does make a difference what motor you are trying to tune. Big chevys (454) 36 max depending on compression and type of induction. 502's don't like much over 32 degrees total. Supercharged motors 30 degrees max. If you are running 10:1 compression on pump gas you may want to limit the timing to 32-34 degrees total. If your motor is running lower compression numbers you have a bit more room to play with. Good luck. Jim :)hand
 

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E-7 Sheepdog (ret)
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According to various laws of physics, it takes a finite ammount of time, in milisecconds, for the mixture charge in an engine cylinder to burn after spark ignition.

Within a very small range, this "burn rate" does not change. Turbulence in the combustion chamber does affect it, but not much.
The exact blend of fuel affects it, again, not very much, unless you completely change the base fuel (alcohol or parafin (diesel fuel) vs. gasoline).

In order to get power from expanding heated gasses (which is how and internal combustion engine generates power), you need to ignite the mixture before the piston reaches TDC, or the piston will be moving away before burn is completed, reducing the pressure pushing on the piston. This is why firing AT TDC is a theorhetical used to teach how the engine works, but, is incorrect in practice.

The ammount of "lead time" (or "advance) you need to ignite the mixture is not the same at all engine speeds. Since the piston speed changes, and the mixture burn rate does not, you must ignite the mixture earlier the faster the piston is moving, to stay the best ammount "ahead" of it to produce the correct ammount of pressure, to produce power.

After a certain ammount of advance, even this does no more good, and only ignites it too early.

That's the basic primer version.
 

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Sean I havent thoroughly read this thread , but put the initial at 8 to 10 run 36 to maybe 38 ttl (all in at 2500) take it out and "stand on it" and BTW I'm increadibly Honored by your siggy line :D Thanks Tom
 

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First you didn't say what type of ignition system your running so some systems are easier to set up than others.If you do not have a MSD I would strongly advise you to save your money and invest in one as soon as possible.Most any good system will fire your engine but the MSD was built with ease of tuning and max performance in mind,they are simple to adjust and nearly bullet proof.When it comes to jet boats and timing you need only worry about setting total advance and make sure your full advance by 3000 rpm. Full advance should be 34 to 36 degrees so set it there and don't worry what the idle timing is. If your idle RPM goes up to much then adjust it down at the carb.You can calculate your idle timing by taking your total timing and minus your mechanical advance. Example: total timing =36 degrees. Mechanical advance =16 degrees. 36-16=20 so 20 degrees will be your inital timing. I run a MSD on my 509 with the timing locked(no advance) at 36 degrees(another benifit to the MSD). this works very well on a jet boat and makes timing easy since your always at the same timing wether at idle or wide open. I'm sure some one will tell you that if you lock the timing your starter will drag when cranking the engine,if you have a good starter and battery it will not drag when cranking. should you still be concerned MSD makes a starter retard box just to drop timing when cranking the engine. Good luck.
 

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Have you set it/checked for total advance/timing yet?? To most, that is the most important. Assuming your pointer is correct. If you're at 4*(initial) you may benefit from more timing. Like thatguy said 35 ish for total is a good starting point.
 

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E-7 Sheepdog (ret)
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I PERSONALLY feel that it is easier starting, and less strain on starters, to use the mechanical advance in my distributor on my Miller.
However, I have "set" my distributor using the MSD spring and bushing kit to "dial in" only 14 degrees of mechanical advance, with the light springs having all of the advance in by 2200 RPM+-. (21* at idle)
What this means is that, basically, as soon as I start accelerating off idle (1000 RPM) it starts dialing it in and is almost immediately at full advance (2200-2400 RPM) It is in effect "nearly" locked out, but with a little mercy dialed in for starting.:D
I played with it extensively trying many different spring, weight, and bushing configurations, but always ending up at 35* total. Different ways of getting to 35* is what we are trying to maximize.
By using the adjustable, inductive timing light, we can record advance rates, total advance by mech., and vacuum means, and RPM that each stage happens at.
I run 35* total, but, did not want more than 8 to 12* or so at idle and so I run the 25* bushing in my MSD Ready 2 Run, with the lightest and seccond to lightest springs in it (1 ea), so as to not get any advance right at idle.
My idle is under 900RPM, and that setup starts my advance coming in just over 1,000RPM, and is all in something in the 2500RPM area.
Works absolutely great in my old cruiser sled, not interested in wasting half a summer trying every possible permutation of parts to try to find 1/2 a HP that I'll never be able to tell is there anyhow.
Starts easy, runs crisp, clean, perfect throttle response from idle to just shy of 6-grand, could not ask for more.
 

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Nice, I assume this locks in your mechanical advance at full advance?

If one was to want to buy an MSD Ignition for a jetboat which would be the choice? For a non-high horsepower jet, just a regular, stock type motor, no blower, 16:1 compression or nothing like that, just 9.5:1 with oval port type heads?
 

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Discussion Starter #11
BTW I'm increadibly Honored by your siggy line :D Thanks Tom

Dude.. I laughed so hard when you put that in that thread.. I called no less than 3 people to share i was laughing so hard...

First you didn't say what type of ignition system your running so some systems are easier to set up than others.If you do not have a MSD I would strongly advise you to save your money and invest in one
MSd distributor control box and rev limiter. I swapped out the mixed and matched precious set up with all MSD...

Have you set it/checked for total advance/timing yet?? To most, that is the most important. Assuming your pointer is correct. If you're at 4*(initial) you may benefit from more timing. Like thatguy said 35 ish for total is a good starting point.
No i have not.. I lost my co-pilot... i got a replacement this weekend to help sort it out.. Standing on the gas and sitting in the engine compartment is hazardous to my health.


Iwith the lightest and seccond to lightest springs in it (1 ea), so as to not get any advance right at idle.
I swear to god i am a moron.. I tossed those extra springs.. need to buy new replacements...;)



Any way thanks guys for all the good info. this gives me a great place to start
 

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I run 35* total, but, did not want more than 8 to 12* or so at idle and so I run the 25* bushing in my MSD Ready 2 Run, with the lightest and seccond to lightest springs in it (1 ea), so as to not get any advance right at idle.
My idle is under 900RPM, and that setup starts my advance coming in just over 1,000RPM, and is all in something in the 2500RPM area.
Works absolutely great in my old cruiser sled, not interested in wasting half a summer trying every possible permutation of parts to try to find 1/2 a HP that I'll never be able to tell is there anyhow.
Starts easy, runs crisp, clean, perfect throttle response from idle to just shy of 6-grand, could not ask for more.
I have the exact same distributor. Sounds like we are real close in our set ups.
I did it all in one day, last summer, mostly to see how the different set ups responded.
I get a little better idle while cold with the higher initial, but I am also over carbed with the 2 660's, I think.
But it works pretty good the way it is.
I only ever have 1-2 people in it, don't pull any tubes, and it is either at idle, or over 4 grand, so it works for me!:)devil
 

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Discussion Starter #13
it is either at idle, or over 4 grand, so it works for me!:)devil
Wait a minute.. you mean a jet boat does not have to run either at idle and WOT? I thought it was just one or the other :)devil
 

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Living in a cage of fear
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Wait a minute.. you mean a jet boat does not have to run either at idle and WOT? I thought it was just one or the other :)devil
Only when Debbie is driving!!
She idles until my ass is 1/2" from being on the passenger seat, then it goes WOT and stays there until I scream at Her.:D
Sometimes I wish I didn't know what all those little gauges mean either!:|err
 

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How does the octane affect timing. I'm running 100 LL and have heard that you need to run a little more timing with it. Motor is a ZZ502 with full Msd and tunnel ram with 660 center squirters.
 

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How does the octane affect timing. I'm running 100 LL and have heard that you need to run a little more timing with it. Motor is a ZZ502 with full Msd and tunnel ram with 660 center squirters.
Higher octane does not require more total advance. It "allows" you to run the proper total advance with out detonation.

35* is 35*, If you have high compression, you will not be able to run 35* on regular fuel.
 

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E-7 Sheepdog (ret)
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Only when Debbie is driving!!
She idles until my ass is 1/2" from being on the passenger seat, then it goes WOT and stays there until I scream at Her.:D
Sometimes I wish I didn't know what all those little gauges mean either!:|err
That would be my old friend Christina.

Couple years ago she met me @ a lake I was @ for the weekend, and I showed her how, and let her drive.

Lake was 9 miles long. The only time we backed off WFO was so she could do some neat power sweeps (not Jetaholics dohnut spins) muscling the boat arround tight corners on the drive power, like a jet-ski on steroids, then on toward the far end, toes in the carpet.
Never saw a bigger grin on her face, even back when we used to date. :D

The only gauge that was not doing what I wanted, was the GAS GAUGE. :D
16.9, 15.9, 14.9, 13.9, 12.9, 11.9, 10.9, 9.9, 8.9, 7.9, 6.9, 5.9, LO LO, LO, LO

Oil press stayed @ 58psig.
Temp was 135*,
Tach was 5,000 (before I had the heads done, 5 was her max),

I drove back, to nurse us all the way to the ramp, and got us there, likely on FUMES. :D
 

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Mallory Halls Effect

I have a Mallory distributor and control box in my jet. It says "not for marine use" to skirt any liability issues. The box has 6 micro switches and allows the user, ME, to set the advance curve 8 ways from Sunday......I can choose WHERE the timing advance STARTS, how MANY degrees per 1000 RPMs, and a MAXIMUM (all in) advance. All at the flips of these little tiny switches. To me, this is high tech stuff. I don't remember all the numbers I used last time out, but the system seems to work very well and can be changed very simply to "be happy" with the "fuel of the day's" octane.........Only mistake Mallory made was requiring the box to be un mounted to access the switches under the BOTTOM cover. Stupid way to do it, so I modified the mounting hardware to access the "bottom" from what is now the "top". They also used 2-56, little tiny screws, to hold the cover on. Also stupid, and now 10-32s with knurled nuts on tether cables so they can't be dropped/lost........This same distributor was also used quite successfully in a 68 Camaro BBC drag car........"Not for marine use", my ass, works great on an open engine..........Ray
 

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Discussion Starter #19
Well.. i got out of the water. Instead of screwing with it i called a buddy who is the lead Dyno tech with Hendrick Racing to come out and give it a whirl......



Needless to say she runs a hell of alot better. thanks for all the help guys. A

lso


Im looking to trade my carb 850 CFM holley double pumper for a similar 650, strait trade. that 850 is just too darn big for that 350. If you got a 650 and looking to upgrade to a 850 let me know.
 

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E-7 Sheepdog (ret)
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Well.. i got out of the water. Instead of screwing with it i called a buddy who is the lead Dyno tech with Hendrick Racing to come out and give it a whirl......



Needless to say she runs a hell of alot better. thanks for all the help guys. A

lso


Im looking to trade my carb 850 CFM holley double pumper for a similar 650, strait trade. that 850 is just too darn big for that 350. If you got a 650 and looking to upgrade to a 850 let me know.
PM'd Del..................
 
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