ballon78

Because the TB V Ignition needs to be in BASE TIMING MODE to set initial timing, can it be set to something other than the 8 degrees (454 mag)that Merc recomends?? My ECM is a 454 MAG modual, but ii have a 502 mag, what should i time it at. If i set the base, to say 10-12 in base timing, will it screw up the computer and try to bring it back to the 8 at idle with the knock sensor a so on..

The tunderbolt V adds and removes timing and tries to mantain idle at 650 by changing the timing so im not really sure how the base timing works or if it has to be set at 8.

idle changes alot, and hangs at 1000 sometimes.

Griff

I don't think a TB V can retard the timing more than what it is set at on base timing. I just don't know enough about TB V's and how they work to give you any answers for sure. You could always try bumping it 10-12* and see what happens. I can't see it hurting anything and the knock sensor will pull timing back if its too much in the higher rpms.

prostockcat

iTrader: (1)

get an advance light and set it at 34 at 3500 rpm.

FIXX

iTrader: (2)

What griff said is true,the only Way it will pull timing back if their is some kind of knocking noise in the engine..try having your friend tap on the knock sensor while you watching the timing mark,it should retard on every tap..you can also unplug the knock sensor and stick a probing tool in the tip of it,touch the prob and use your other hand to touch ground,this acts like a resister and the timing marks will move also..

if it were my boat i would get rid of the tbv ignition and go with msd..

similar problem with a friends boat last week,,boat ran fine except the rpm was up and down,idle fine for a few minutes then it would stumble to a lower rpm....turned out to be water in his 5/7 exhaust ports causing the engine's rpm's to be unstable..if your rpm's are set high this could be the same problem your having...he was running dana marines manifolds and it turns out dana had a bad batch of manifolds that had the mounting flange bolts drilled wrong and it covered half the exhaust ports which caused reversion..the engine prior in this boat was blown up(cyl 5 piston shattered) due to water being in the cylinder..

Boat Tech

All base timing mode does is stabilizes the timing so that you can set the timing with a timing light with out the light bouncing all around while your trying to set it where you need it, It will also help you adjust the idle speed down.

Then when you unhook the ground wire the timing will start to fluctuate up and down a few degrees as needed to help control for a smoother idle, But your initial timing will always be based off of where you set the initial timing of 8,10,12 degrees, then the module will add to that set number as needed within it's set program as you advance the throttle.

Not sure what your going for, But if your idle is around 1000 rpm's, I would not recommend shifting into gear at that speed.

Also if your timing is up that high and your carb is not adjusted right or even the tension on the throttle cable is not set right, All that being out of sync could give you different rpm settings everytime you try to idle. Unhook the throttle cable off the carb when you try to set everything up, Per the service manual, Then adjust your cable for your new adjustments.

I personally like to set the timing right at 9 degrees on stock engines, With a idle speed of 643 - 648 RPM's, To me that just seems to run the best, But don't for get to set your idle mixture screws also.

I hope you have the mercruiser service manual to help you with all of this? Good luck with it.

ballon78

So is the 650rpms what i want in gear idling or in neutral. I have a merc manual. thanks for your help

Boat Tech

First take your time with adjusting everything at home in neutral, Then take it to the lake and see if it stays at the same idle speed in gear under load with engine warmed up, If not readjust as needed. Because you have a holley carb, Your idle in neutral may end up a little higher than 650 when you take it out of gear in some cases.

Also be patient with it, It can take some time to get it just right, Good luck.

smokin' gun

iTrader: (30)

saw you out last weekend me and my friend were at the dock @ abbots where you turned around . you should have come over maybe we could have helped or at least take a look . stop by sometime we run the river every weekend

ballon78

Sounds like a plan, today is way to windy to mess with it.....Just got new alum trailer, so im tring to get it all set up right now. maybe next weekend, I have seen you out last year i think, im always in the river, i put in at larry's, sometimes leave my boat to houses up at my friends house he has the Checkmate. let me know i fyou will be out at all, i may put in this week after work to straighten things out too.