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Timing pros an cons

Snapper man

Active member
Av 0540 electronic ignition, timing is set 15 degrees btdc? Up to 2600 rpm pushes like a dozer, not complaining there. Over 2500 seems to break up and hesitate? 72in we 3 blade I know it should be timed at 25 degrees btdc but low end push is so great I hate to mess with it. Any suggestions
You should be able to set the timing to whatever you choose at whatever rpm. I'm not too familiar with the electronic setups on air boats but even the cdi on my 4 wheeler can be set up like that.
Snapper Man,

What ignition system? I believe you are running that motor on an 18 footer, so it is working pretty damn hard, I assume you are laying into that 2,600 RPM and above pretty hard and for long duration? You may be having the same issue as I had recently running extremely hard in afternoon sticky dry. In that situation I am pretty sure the plugs turned into glow plugs, causing pre-ignition. For me, all I had to do was lay off the throttle for maybe 15 seconds and it would cool enough to run hard for another minute or two.

What is your oil temp when this occurs? Any chance you have CHT sensors (Cylinder Head Temp) installed? I am working on trouble shooting the issue on my end. I pretty sure the primary cause for me is hot cylinder temps, but I want to know what is going on, so my first step is installing CHT sensors and gauge, which I am close to completing. Then I will baseline it to find what cylinder temp causes the problem. Next I bought aviation copper spark plug gaskets to improve heat transfer vs. the steel gaskets and try again. I then expect that I will need to add a cooling shroud to get my CHT's down.

Versus mags, I believe the key issues are a hotter spark and the fact that electronic ignition fires the spark plugs every revolution, so they are firing at double duty vs. Mags and not getting time to cool off. If the motor is that hot, then I need to cool it regardless of what the ignition is doing. I was running 25 BTDC when this occurred, dropped timing to 22 degrees in the field but the problem did not resolve (it sure was nice doing this with a screw driver vs. timing the mags back in!). The fact that you have set your timing down to 15 degrees and still have the issue re-enforces my thinking that your plugs are overheating.

One final note, so far my research says that the heat range 6 is as low as they go with the 18mm resistor plugs. There are adapters that will adapt the 14mm thread plugs to the 18mm cylinder threads. Once installed there is a large range of plug heat range options to choose from. I read some aviation forum threads where the plane guys say the Autolite 386 plugs gave them detonation with electronic ignition systems under hard (climbing) load, so they were recommending the adapters and alternative plugs. So this is another item on my "may have to do" list.

You are going to owe me a whole bar tab if this keeps up :p
It's just a 13 1/2 foot and I didn't set time there that's as far as it goes. Short version, the motor had mags on it when built with elec ignition installed afterwards. Try to decide if I want to turn timing gear 1 tooth or leave it alone. The system is a Charlie bass ignition and I dont need to run over 2500 to go anywhere desired, run dry all day the ridge or whatever. Motor never runs over 160 temps. Stick with a NFL ab6 or denso l 14 u best 2 pugs . Heat might be to cause by 25 d btdc while running pump gas , if you do that advance to 20 or more. Now you owe me a beer
I love the old style Charlie bass set up . If 1 side goes out I can run on the other. It cranks on 1 or both. Both of sides have a start and run module and parts are easy to get. Cranks easy idles immediately smooth.
Switched to electronic to eliminate electronic interference with my dog tracking gear. Considered Aviation harnesses and plugs first but figured I would give electronic a try. I run AV gas exclusively and my mags were set at 26. With mags I would get into detonation too if I don't keep the motor cool, it just came on sooner and more abruptly after the changes. Either way I run it hard and intend to figure out what I need to do to keep it cool while running hard. The problems developed on the second time out, admittedly pushing things hard. As you can see, still doing test and tune on my end.

I am not familiar with the Charlie Bass units, I assume they bolt in replace the mags so they would time off the cam and not be subject to firing on the exhaust stroke. Is it a fixed timing system? 15 deg BTDC is pretty low for top end RPM if timing is fixed or that is the all in setting. Running too little advance will kill top end torque and burn the exhaust valves eventually as it increases the exhaust temp. I agree with GMAC's input on bumping timing up. He said at least 20 but I would go all in to factory spec at 25 unless you know of a reason it was set at 15?? It sounds like you need to advance a gear to get the timing where it needs to be and that probably resolves your issue.

Thanks for the input on plugs. I ran Champion UD16 plugs previously with mags. I have not tried the RD16 plugs yet, but that is on my list of stuff to try. That Denso is a hotter plug than I am running I believe (hard to compare, they all use different scales), the NGK is in the same heat range, but both are non-resistor plugs. I have to use resistor plugs to achieve my radio needs, so that limits the field more. One other point I did not make previously, the plugs are presently gaped at .038, which is too much for mags but fine for electronic. I plan to test smaller gap to decrease plug temp on my end.

You never know on the beer, I loose count of them anyhow!
:rebel: I run 8mm wires ,resistors and use an alpha 100 and garmin drivetrack 71 and so far have no issues with interference? Your correct on running to hot or bigger gap will cause detonation, wondering if that plus timing is causing my top end rpm hesitation. I will check on the brand wires I have, if you cant find them I've got 2 new set up I can hook you up. Didn't realize I would ever talk to anyone else that runs dogs off an airboat. We are definitely the only club I know of in new FL that does it every weekend. And one other thing you reminded me off I need to lower the gap on my plugs to around 35ish. My ignition times just like a car motor I'm just out of adjustment, that's the reason I was posting about turning 1 tooth on timing gear by on and we both can have to many
One thing you say confuses me. You say you run resistors. I assume 8 mm resistor wires, I ran solid copper with mags but have resistor wires on now. But the plug numbers you gave previously are non-resistor plugs, at least from the specs I looked at last night? You are saying you get no interference running those non-resistor plugs?? I have an old tube TV in my shop, it’s an easy way to check for EMF interference, just light up the boat and if the TV goes bonkers there is a problem, mags and solid wires definitely sent it for a loop.

If you change timing to 20-25 and still have the same issue or worse, then your issue is not due to retarded timing, detonation would be the culprit. Consider this, if you light up the boat and give it a mild warm up before going straight to WOT, does the motor act up at full throttle or does it make power? If it acts up right off the bat when cold, then retarded timing would be my thinking. If it runs strong for a bit until it heats up and then acts up, detonation would be my suspect.

There are quite a few of us running dogs, buggy, Airboat, mud boat, kicker boat, trucks and on foot, what ever is legal and the best option for a hunt. I can't believe 70% of Floridiots decided dog racing is in-humane, WTF :banghead: Dogs like to run, mine do. What's in-humane is making them nut less so they sit on the couch and eat bonbons with you. I might have to get me one of them Greyhounds to try out, tried every other color hound. I will send you a PM. :thumbleft:
You are correct , I stated that wrong . Solid core wires but when making up the ends you could see they are twisting strands of wire wrapped in some kind of fiber for low or high resistance. But no problem with electronics at all. Totally agree on the dogs , ours are never happier than when running
Not an electronic ignition guy. And it very well could be causing that top end breakup. I’ve had the same thing on a boat r two. Both times ended up being a fuel restriction or pump not keeping up.
Snapper man said:
Got it all fixed, timing was the issue, this thing is a beast.
Snapper man,
Can you elaborate? What was the problem with your timing setup and what exactly solved it?