Offshoreonly.com - Carburetor (dominator) Recommendation

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I called and spoke with Dennis at Daytona and he’s inclined to believe it’s something else in the ignition system. Rusty reluctor or mag p/up, told me to look for cracks in the plug wires.

Its not much money or effort to replace cap, rotor, p/up and reluctor. So I think I’ll go that route. I think the wires are fine. I hate to change too many things as it may not reveal the true solution but I don’t care at this point. MSD makes a EFI reluctor that’s adjusted 10*. I’m thinking of going that route as it would apply to Daytona Sensors as they function the same as EFI timing in that everything that happens is based on delay. The delay brings up the question of rotor phasing especially in stock EFI where you are delaying more than 22.5* which would put the rotor more than 1/2 way to the next spark plug. I could try the adjustable rotor but I like the idea of the fixed offset reluctor.

I’ll definitely check the logs. I also just realized that I had 2 yr old fuel mixed with a small amount of fresh fuel. Don’t know if that’s creating a scenario making it hard to fire a cylinder and forcing the spark to go to another cylinder that has less pressure and creating a path of lower resistance. Anyway I was almost out of fuel yesterday and have since filled up. The first start up yesterday, which killed the starter was with the remaining old fuel in the bows. After that it started fine 3 or 4 times for the rest of the day.

I’m still inclined to give Daytona the benefit of the doubt and think it’s a combination of almost max retard and some other scenario creating a perfect storm.

I think if the timing spike on the datalog is there again, I would look at the distributor components too. The datalog is pretty much showing you what the box is doing , before the spark actually occurs . For example, you can program the box to have 25* at 3000 RPM, and set the timing with a timing light for 30* at 3000, and the datalog will still show 25* of timing on it. The box doesn't know whats happening after it triggers the spark. The rotors position relative to the cap isn't seen by the box.

Now since the datalog is showing a spike in timing, I'd have to think it was something that affects the box's input signals. Reluctor wheel, magnetic pickup, etc.

I think what I would do, is replace the starter. Then, remove the coil wire. Do a bunch of cranking tests. Datalog it, and look for those spikes again. Then, replace the reluctor and pickup, do some more cranking tests, datalog again to be sure there are no more spikes in timing.

As far as starters go, the old school starters are tougher than the new gear reduction ones. They are big and heavy, but the gear is much better supported on them.

Good idea about data logging the starting tests. As for the light duty starters, I think I like them and here’s why, it’s always the weak link that fails and I’d rather have the starter be the weak link then the flywheel. When there’s no kickback the starter does a great job it just loses the fight when things aren’t right. At $75 each and 20 minutes to change I think I’m just going to buy a spare to keep on hand.

I agree with what MT said.......very, very good info and spot on ! To reiterate and quote one of statements to keep in one's head:

Quote:

The rotors position relative to the cap isn't seen by the box.

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Mt has also touched on a few things about the starters I'd like to know from the OP. Do you have the old school large starters ? If so, do you have the nose support bracket attached ? And if newer style like hitachi or PG260 what broke on the starter ?

Lets think about this. Say you didn't have a Daytona box and you were simply going to run locked timing. 34* locked would put the rotor to cap terminal further apart, than you would at 20* of timing. any chance of crossfiring, would be more likely with more timing, than less, when using a pro billet type distributor.

if you were to line up your balancer at 0*, and look at the reluctor wheel, youll see its right in line with the magnetic pickup. however, if you rotate the balancer to 34*, youll see the cap to rotor is off quite a bit, as well as the reluctor wheel to pickup. GM knew this, and on their electronic controlled distributors, they actually came pre-phased/pre=synched. on those, if I recall, when you lined up the balancer to around 15-20*btdc, the reluctor wheel was in line with the pickup. on a msd pro billet that's locked, the closer to 0*, the better the rotor to cap terminal relationship is.

Quote:

Originally Posted by SB (Post 4649394)

I agree with what MT said.......very, very good info and spot on ! To reiterate and quote one of statements to keep in one's head:

==============================================

Mt has also touched on a few things about the starters I'd like to know from the OP. Do you have the old school large starters ? If so, do you have the nose support bracket attached ? And if newer style like hitachi or PG260 what broke on the starter ?

I’m using the gear reduction starter that Merc has used on a lot a BBC with top mount starters. I believe it’s reverse rotation. The first 2 were made by world power systems and the third came from NAPA.

The damage is internal as there are no visible signs on the outside. The 1st failure started sounding really strange, whinny. The second just spun free as if the solenoid wasn’t extending the starter gear.

MT, the reluctor and rotor relationship is fixed with a stock rotor and the reluctor is essentially directly connected to the balancer. As the timing is adjusted the cap and mag p/up move together changing when the firing sequence starts. I’m guessing MSD knows how long it will take for the p/u to receive the signal and the spark the reach the tip of the rotor and as such they phase the rotor to the reluctor accordingly so that the tip of the rotor is the right place to deliver the spark to the cap. I wouldn’t think this rotor to cap relationship would change when the timing changes because as you move the the cap you also move the pickup.

However when you ad retard you change the amount of time it takes for the spark to get to tip of the rotor and thus the rotor is no longer in the position MSD originally thought it should be in when it’s time to pass the spark from the rotor to the cap.

What i I don’t know is where exactly does MSD put the rotor and as such where does it end up when you delay the timing for 22*? Apparently there’s enough of a concern about where the rotor is when you delay the timing and that’s probably why MSD makes and adjustable rotor and also the EFI reluctor that’s compensated for this delay. I’m surprised Daytona doesn’t mention anything about checking rotor phase.

Quote:

Originally Posted by ezrizer (Post 4649421)

if you were to go out to the boat, remove the cap, and put the balancer at 0. Youd see the reluctor is perfectly in line with the pickup. Like you said, as you move the cap, the pickup moves, but the rotor shaft and reluctor does not. So, what you end up with, is a need to phase the rotor when the timing is fixed, or say, excessively advanced or retarded.

with a reluctor wheel that is lined up say at 20* btdc, you now have a better rotor position because you are starting off centered on the cap terminal at 20* btdc.

The easy fix is the adjustable rotor on a msd. Gm wasnt going to put an adjustable rotor on a production vehicle. At least thats how i interpret it, may be wrong.

at any rate, you may have mentioned it, but did you check the air gap on the reluctor to pickup?

Daytona does give information in their instructions on how to phase the rotor. My personal opinion is that a crank trigger should be used with the Daytona box. It works so well that there is no reason to do it any other way. There is a reason why they put 4' of wire on the trigger.

The only real mention of rotor phasing is in a section discussing crank trigger which I only glanced over because it doesn’t apply to me.