Jet Boat Timing/Advance Curve

[Jetaholic]

Here's a good question that was posed to me recently...and it has me wondering the same thing.
I am still trying to figure out how the timing curve is where it is at with jet boats - Seeing how the boat doesn't move until you are past max advance anyway... I can see it in a low stall vehicle because the curve is maximixing the torque curve while it is accelerating (may be several seconds worth of acceleration time) but a jet with a couple milliseconds of acceleration time???? How is that gonna help?
So my question is...where did the "max advance in by 3,000RPMs" timing curve come from? Where did we end up with total advance number such as 34*, 36*, 38*, etc etc? What is the purpose of having it all in that quickly?

[IMPATIENT 1]

Here's a good question that was posed to me recently...and it has me wondering the same thing.
So my question is...where did the "max advance in by 3,000RPMs" timing curve come from? Where did we end up with total advance number such as 34*, 36*, 38*, etc etc? What is the purpose of having it all in that quickly?
all is quickly gives great throttle response. i haven't used a advancing dist in yrs. though, i like em locked:D my new set-up is gonna be set at 36*, under starter it'll retard 20*, and under nitrous i've got 3 stages to retard for that:D
oh yeah, bbf rule:D

[Jetaholic]

oh yeah, bbc rule:D
Fixed :D

[Widetrack]

Fixed :D
Dist. is locked out no movement of timing plate. MSD has a bolt in the plate you change locations on and the advance does not move anymore. Heads up timing. When you set timing @ 36* it stays there and you might have to put a start retard to reduce start timing!:idea:

[H20MOFO]

For what its worth my initial is 25ish and total 38 ish and mine turns over fine. I probably should have just locked it all the way but I didn't. I think i read once in ***boat mag when your initial gets past like 17* the starter is no longer "bucking" the compression. I can't remember why.

[cyclone]

in most jets, the engine will rev faster than the advance can operate. its easiest to just lock out the distributor and if you have problems starting the motor, just get a start retard box. my motor has a healthy amount of compression and i have no problem turning it over without a retard box.

[Wazoo]

Depending on your engine combination, compression, type of heads, etc. That can all have a effect of where you run your total timing. 32-36 is the usual area. That may or may not work for you. A couple of degrees can effect top end HP. Your pump is a dyno. Play with it until you get max rpm. If it spark knocks back it down. If it's to hard to start. Back it down. This sounds hairy but I have had somebody driving while I adjusted the timing at full throttle. It was amazing how it effected rpm. The safe way would be to stop and adjust a little at a time. Then hit the gas and see where you are at. There could be a couple of hundred rpm hiding there.:sqeyes:

[Wazoo]

By the way. Lock the advance. You don't need it with a jet. Just like Cyclone said!!!

[Jetaholic]

By the way. Lock the advance. You don't need it with a jet. Just like Cyclone said!!!
That's exactly what we were thinking...why are we even setting an 'initial' timing between idle and 3,000 RPMs anyway when most jets don't even plane until your above 3,000 anyway?

[Outlaw]

For what its worth my initial is 25ish and total 38 ish and mine turns over fine. I probably should have just locked it all the way but I didn't. I think i read once in ***boat mag when your initial gets past like 17* the starter is no longer "bucking" the compression. I can't remember why.
yeah I read the same article, by Timinator

[Wazoo]

That's exactly what we were thinking...why are we even setting an 'initial' timing between idle and 3,000 RPMs anyway when most jets don't even plane until your above 3,000 anyway?
Sometimes it's hard to get the motor to idle down with the timing cranked up. If that matters to you. Sometimes with a hydraulic cam it's nice to adjust that baby in where it sounds just right.

[Jetaholic]

Sometimes it's hard to get the motor to idle down with the timing cranked up. If that matters to you. Sometimes with a hydraulic cam it's nice to adjust that baby in where it sounds just right.
And there you bring up an interesting point on the idle speed. I've always been a big fan of getting the motor to idle as low as it possibly can. However some jet guys add a few hundred RPMs so they don't have to keep their foot on the throttle through the no wake zone and just control the forward speed with the forward/reverse shifter. However I love hearing my motor at a super low idle and hearing that cam overlap.

[HammerDown]

Good topic...

[H20MOFO]

If anyone wants to read the article it's feb 07 , on page 122 it basicaly says why worry about optimizing performance below 3000 r's in a jet? And then says how can an engine even start at 38* if the starter "bucks" compression at 16* then the timster explaines it. For some reason my engine start/idles better with more adv. the article also explaines how different set ups will require more total timing, things like open chambered heads and higher octaine fuels will need more adv. GOOD ARTICLE TIM!

[396_WAYS_TO_SPIT]

Oh and by the way
Lock out your distributor :D

[1968Droptop]

Fixed :D
Had to work on that GM product again :) :) :)

[speedymopars]

It's funny watching you guys battle it out for number 2! :D
like I said - curve is unimportant in a jet...only total timing is...
Vac advance can get you part throttle cruising mileage, but whether the mechanical curve finishes at 2K or 3K, doesn't matter.

[Moneypitt]

I am glad to see there are so few jet ski boats left. I guess all the water sports people are using the wakeboard boats today. IF you want to pull the kids in tubes or on skis, I strongly suggest a timing advance. Sure, if you're just matting the gas all the time, no problem......However, to gradually pull up an inexperienced skier you need a strong steady pull through the idle to ski speed range. Also, lower rpm power is required pulling skiers on speed limited lakes. WOT on plane needs very little "crutch". It is the transistional area where a perfected timing curve can make an average skier look great, or a great skier look average.......Afterall, jet boats ARE great family recreational boats, not race boats.........MP

[steelcomp]

Ditto on everything above excepet this:
I've always been a big fan of getting the motor to idle as low as it possibly can. That's really hard on an engine, especially with a flat tapet cam. An engine should idle where it's not sounding like it's "laboring". It may sound cool, and if that's what you;re in to, that's cool, but just know it's hard on it.
Usually at idle, the higher the timing, the higher the vacuum, and that will always help idle quality and throttle response. Timing curves are for when there's a certain amount of load on the engine at lower rpms...too much timing can cause detonation at lower rpms, so to prevent that, the timing is slowly advanced to it's optimum, where rpm and cyl pressure reach a point where they can take advantage of the lead. Reduced timing also makes it easier to start the engine. In a jet, there's so little load at anything but full throttlte that it really dosen't need a timing "curve", and typically will take full advance. My 467 with 12.4:1 started with no issues with no start retard and 34 degrees total.

[396_WAYS_TO_SPIT]

My 467 with 12.4:1 started with no issues with no start retard and 34 degrees total.
Copy that Scott. I ran a 461 BBC 12.5-1 and it started without any issues. I will be running a retard box on my new motor just to play it safe.
Or you can go old school and wire in a switch and a starter button. Push the starter button and get the motor cranking. Next, flip the switch while its cranking and BAM, your angine fires immediately without any issues......

[396_WAYS_TO_SPIT]

or wire this bad boy in and be done. I will be running one of these
http://www.msdignition.com/tc_images/pn8984.jpg

[396_WAYS_TO_SPIT]

Starter Saver with Signal Stabilizer,
PN 8984
When you install a crank trigger system, having locked out timing may put a strain on the starter and flywheel. This compact controller provides a retard that automatically retards the timing during cranking to ease the pressure.
The MSD Starter Saver measures only 1.5”x 3.5” x 2” and wires into your ignition system with only four wires. It can be programmed to retard the timing 10° or 20° during cranking only. The retard is activated when the engine begins cranking and is deactivated once the engine reaches over 800 rpm. (If the engine rpm drops below 500 rpm it will activate again.)
The Starter Saver receives the trigger signal through an MSD Crank Trigger pickup or the Distributor’s magnetic pickup. This Control has a very accurate pickup compensation circuit resulting in rock steady timing throughout the entire rpm range of your engine. There is also an LED that illuminates with each trigger signal to confirm operation and the circuitry is completely potted in a polyurethane compound for extreme vibration resistance.
This is a little info about it............