chasing a gremlin.....

Aircraft powered airboat discussion.
User avatar
mojoe
Southern Airboat Member
Posts: 953
Joined: Thu Jul 23, 2009 8:55 pm
Location: Catfish Motel

Re: chasing a gremlin.....

Post by mojoe » Tue Feb 02, 2016 7:31 pm

DB

No, I am no expert either.
diamondback0320 wrote: jopete I understood what your thread was about.. Was just reading a response of somebody talking bout taking off positive cable when in around the motor I guess believing that that has any affect on the mags..which does not,I think lmao!
Yes, I am also glad jopete found his bad connection.
Gary S wrote: I don't use battery switches never found a need fore them. If I am working around prop I remove the positive battery cable.
Yes, that is not effective in making an aircraft motor safe

Yes, this thread has taken an unexpected turn.

So in the interest of learning and safety, I will try again:
jopete wrote:yep, when i work around the prop, perko switch is off, positive wires pulled off the battery, and all switches off on panel.
The Positive cable off disengages the starter and othe electrical stuff.

If the perco is on the positive and off, disconnecting the positive isn't necessary.

My question is about if the the perco is on the negative. Does that disable the mags?
CactusJack wrote:
Yeah, that is why people need to take off spark plug wires if planning to turn the crank of a motor on the bench... it might fire if it has mags and plug wires connected....
How does the electricity flow through the plugs into the motor without a place to go?

Yes, they still make electricity. Yes, it has the ability to go through the plug wires and to the plugs. Yes it has the ability to go through the plugs and into the block. But if there is no ground from the block, will the plug still fire? I thought the plugs needed the ground to the battery to complete the circuit. If the mags create electricity that can spark through the plugs with no ground or completion of the circuit to the battery, do they complete the circuit back into themselves? What completes the circuit? And if the electricity is flowing from the mags to the plugs into the block and back into the mags to complete the circuit, why can't we ground lights, or the starter, or anything else to the block without a good ground to complete the circuit?
Mark 7:9

diamondback0320
Southern Airboat Member
Posts: 1324
Joined: Thu Aug 20, 2009 3:09 pm
Location: palm bay,fl

Re: chasing a gremlin.....

Post by diamondback0320 » Tue Feb 02, 2016 7:40 pm

I'm not really sure..but I'm almost positive you could take a battery completely out of the boat & if the mags r not ground as in the off position or pleads completely unhooked from switch..if there is fuel in carb or cylinder & you hand prop it..it will fire!

Scarecrow
Site Supporter - II
Site Supporter - II
Posts: 1292
Joined: Sun Feb 05, 2012 12:01 pm
Location: west palm beach to sebring

Re: chasing a gremlin.....

Post by Scarecrow » Tue Feb 02, 2016 8:28 pm

I had a 65 cont. years ago and the only time I had a battery in the boat was when I was frogging and then the only thing hooked to it was the light, always hand propped it, never had a starter or gen. :rebel:

User avatar
mojoe
Southern Airboat Member
Posts: 953
Joined: Thu Jul 23, 2009 8:55 pm
Location: Catfish Motel

Re: chasing a gremlin.....

Post by mojoe » Tue Feb 02, 2016 8:40 pm

Thanks. I learned something. But how does it work without a complete circuit? Is the block itself enough of a ground to dissipate the current? Is it flowing on a repeating circuit through the mags over and over?
Mark 7:9

User avatar
mojoe
Southern Airboat Member
Posts: 953
Joined: Thu Jul 23, 2009 8:55 pm
Location: Catfish Motel

Re: chasing a gremlin.....

Post by mojoe » Tue Feb 02, 2016 9:58 pm

For anyone who cares, a little poking around the internet and I found my answers:

The magneto is grounded to the block, or the block to the magneto (however you want to look at it) so magnetos create their own circuit. Magneto>wire>plug>block>magneto

You can't use that circuit as a ground because it has a positive current of a about 20,000 volts.
Mark 7:9

Lwells
Southern Airboat Member
Posts: 327
Joined: Sat Nov 15, 2014 9:18 pm
Location: okeechobee

Re: chasing a gremlin.....

Post by Lwells » Tue Feb 02, 2016 10:42 pm

Diamondback is 100% right on the mag's, whether on airplane engine, car engine, or whatever. Those mag's need nothing, so to speak, to fire. NEVER, NEVER BELIEVE YOUR MAGS ARE OFF OR YOUR FIXING TO GET HURT OR Killed. Mag's are suppose to be safe When they are grounded but never believe that and when around a prop on an engine with mag's never assume the mag's are grounded and safe. Think of mag's like hunters think with a gun, even though they just unloaded it and laid it down for a second when they pick it back up they will check it again ,IF THEY ARE SMART. Just always remember that the wire coming out of the mag is suppose to be hooked so it can be grounded to keep the mag's from firing, but, I have seen a hot engine with the mag's grounded fire from compression and fumes in the cylinder just like a diesel, when the prop was turned by hand. So I can't say enough about being around the prop on a warm or hot engine, or one with mag's. Old pilots have a saying(THERE ARE OLD PILOTS AND BOLD PILOTS BUT NO OLD BOLD PILOTS)

diamondback0320
Southern Airboat Member
Posts: 1324
Joined: Thu Aug 20, 2009 3:09 pm
Location: palm bay,fl

Re: chasing a gremlin.....

Post by diamondback0320 » Tue Feb 02, 2016 11:26 pm

I always look & make sure my switches are off b4 doing anything around the prop or inside the cage..but as you know moisture is very dentremental so I don't 100% trust a switch.. So with that being said if I'm gonna have to turn the prop outta the way while I'm in there I always move the prop in the opposite direction of rotation so that the impulse won't snap in the mag!

Gary S
Site Supporter - I
Site Supporter - I
Posts: 1647
Joined: Wed Mar 03, 2010 3:30 pm
Location: Redlands

Re: chasing a gremlin.....

Post by Gary S » Wed Feb 03, 2016 7:32 am

The reason I said I take the positive wire off is to make sure the starter cannot engage. And yes the only way to make it 100% safe is to take the plug wires off.
If your going to have a battery switch it doesn't matter which side you break as long as everything on that side is opened. You don't want to break the neg cable going to the engine block but have a wire from battery to gauge panel or some other place like electronics. If you forgot to turn the switch on and tried to start the engine, the small wire would try to be tho engine ground and melt.

By the way glad you found your gremlin.

Scarecrow
Site Supporter - II
Site Supporter - II
Posts: 1292
Joined: Sun Feb 05, 2012 12:01 pm
Location: west palm beach to sebring

Re: chasing a gremlin.....

Post by Scarecrow » Wed Feb 03, 2016 9:01 am

I always use 2 ratchet straps and tie off the prop to cage. :rebel:

Lwells
Southern Airboat Member
Posts: 327
Joined: Sat Nov 15, 2014 9:18 pm
Location: okeechobee

Re: chasing a gremlin.....

Post by Lwells » Wed Feb 03, 2016 8:46 pm

Diamondback, I don't know what kind of engine you have but did you know that an aircraft engine will fire and run backwards for a short period of time, I've seen people hand prop them and they kicked back and set there and ran backward seemed forever.
As for the fellow that started this thread just remember that mag's are like little electric generators that will put out electricity anytime the shaft in them rotates, and they need nothing except their internal parts to produce electricity and the only way to stop them putting out electricity is to ground out their internal parts. That is why they have a wire coming out of them(some call a P-lead). This wire is hooked to the internal parts which allows you to hook it to its own separate switch and run the other side of the switch to ground. It doesn't need to hook to anything for the mag to fire, but when it is grounded in the same grounded area as the engine then it will not fire ,UNLESS, SOMETHING IS WRONG INTERNALLY, SO WHAT YOU HAVE TO REMEMBER ABOUT THE SWITCH YOU USE FOR YOUR MAG IS THAT IT WORKS BACKWARD FOR A MAG. Your mag is grounded or off when switch is in on position and mag's are hot when switch is in off position. So your switch grounds the mag when you flip it to on for it makes the circuit complete. When you put your switch in the off position you have disconnected the switch and your mag's are no longer grounded so they become hot. Hope I haven't confused you too much. So your switch is a ground switch, one side to mag, other side to ground.

User avatar
jopete
Site Supporter - II
Site Supporter - II
Posts: 977
Joined: Mon Mar 30, 2009 8:07 am
Location: loreauville, la

Re: chasing a gremlin.....

Post by jopete » Wed Feb 03, 2016 9:18 pm

thanks!! i'm good on mags now!! i never have worried about turning the engine off. this whole thread was about getting the electric starter to start the gpu when i hit the starter button. just like it always has for the last 10 years. lol
ended up being a bad connection on ground wire between battery and engine block.

thanks for all the replies!!

Lwells
Southern Airboat Member
Posts: 327
Joined: Sat Nov 15, 2014 9:18 pm
Location: okeechobee

Re: chasing a gremlin.....

Post by Lwells » Wed Feb 03, 2016 11:12 pm

Sorry about this, I only intended on answering the guy about the mag's but don't know how to post only to that guy in the middle of another post. Hope I didn't upset anyone. Had good intentions :banghead:

User avatar
jopete
Site Supporter - II
Site Supporter - II
Posts: 977
Joined: Mon Mar 30, 2009 8:07 am
Location: loreauville, la

Re: chasing a gremlin.....

Post by jopete » Thu Feb 04, 2016 2:40 am

i am glad that a conversation has started. i have learned more about how my mags work and how my engine should be grounded and mags wired than i ever knew before.
i'm sure i am not alone by saying i enjoy reading these threads and i try to learn from them. years ago i would never have thought i would work on my own engine or be able to troubleshoot a bad wire or ground. i am still not where i want to be yet, but sincerely appreciate the imput from all of you fine gentleman, it makes me think and rethink issues on my boats and improve them.
if you think about how much knowledge is out there in the airboating community, it is amazing. the majority of airboaters i would think are men who didn't start with much, and turned motors/propellers/boats and other things that usually don't go together and turned them into great airboats. much of it by trial and error. lots of ingenuity and sweat. teaching yourself to weld, mechanic, wiring, seting up the hull, and rigging it so it doesn't fall apart every trip is one heck of an accomplishment.

long winded, but just saying thanks, i appreciate everybody's imput on anything, that's how we learn.!!!!!!!

Lwells
Southern Airboat Member
Posts: 327
Joined: Sat Nov 15, 2014 9:18 pm
Location: okeechobee

Re: chasing a gremlin.....

Post by Lwells » Thu Feb 04, 2016 10:13 pm

Joepete I'm just getting into airboats also but my knowledge comes from being a commercial airplane and commercial helicopter pilot for years and years and building 11 experimental helicopters and growing up in a Chevy dealership from age 8 . Naturally I became a mechanic after all the other sh-t details I had to do and learn. After learning I built race cars for 19 years while racing so I have a little knowledge to share once in a while but there are plenty of people that know more than me but I'm able to contribute once in awhile. Its always meant more to me to be able to help someone rather than butt heads with others. I learn from someone every day and that's a good think.

diamondback0320
Southern Airboat Member
Posts: 1324
Joined: Thu Aug 20, 2009 3:09 pm
Location: palm bay,fl

Re: chasing a gremlin.....

Post by diamondback0320 » Thu Feb 04, 2016 11:13 pm

Didn't intend on jumping in & taking over the thread by any means, I have learned a great deal on here also by reading & talking..meeting fine people,Idid aalready understand how the switches worked for mags by reading & troubleshooting myself thru the yrs & still have a lot to learn,did not know a aircraft motor would fire backwards by just turning the prop opposite direction by hand, figured the snap of the impulse fired it..I have seen them run backwards a bit on shut down for other reasons or kickback hand propping sometimes,learn something new everyday

User avatar
CactusJack
Southern Airboat Member
Posts: 1246
Joined: Mon May 25, 2009 8:28 pm
Location: Landsborough, Queensland, Australia

Re: chasing a gremlin.....

Post by CactusJack » Fri Feb 05, 2016 5:28 am

And I am just nosey... and cant help myself :wink: :lol:

After all I am Austr-alien :salute: :stirpot:
Attachments
georgio6a.jpg
I was told I was wrong, once (not sure I believe it though)
If you can't blind 'em with brilliance, baffle 'em with BS
Airboat experience so far, limited to having bolted a gyrocopter to a flat bottom punt.... but THAT.... is about to change, bigtime :-)

Lwells
Southern Airboat Member
Posts: 327
Joined: Sat Nov 15, 2014 9:18 pm
Location: okeechobee

Re: chasing a gremlin.....

Post by Lwells » Fri Feb 05, 2016 10:36 am

Diamondback, I don't completely understand it myself but I seen a guy turn a prop backwards on a hot engine to put the prop in the position he wanted it and it kicked and run one way a turn or two and then ran the other way couple turns and that's what I was meaning. I don't know whether it fired from compression and heat or what, but I thought we were going to have to lone him a pair pants after it happened and prop hit his hand but not enough to hurt him.

User avatar
jopete
Site Supporter - II
Site Supporter - II
Posts: 977
Joined: Mon Mar 30, 2009 8:07 am
Location: loreauville, la

Re: chasing a gremlin.....

Post by jopete » Fri Feb 05, 2016 1:32 pm

i have had my gpu run backward for a few seconds after i turned my mag off. i attributed it to the fact that i shut the engine down before it has properly cooled off. i had been running extremely hard and shut it down real quick when i got the boat hung up in some trees. lol

Lwells
Southern Airboat Member
Posts: 327
Joined: Sat Nov 15, 2014 9:18 pm
Location: okeechobee

Re: chasing a gremlin.....

Post by Lwells » Fri Feb 05, 2016 2:35 pm

I believe you will find by talking to airplane mechanics that you should never shut an aircraft engine down with the mag's but should shut it down with the mixture control to the carburetor which I've found most people in the airboat community don't install on their carburetors. Also, a mixture control on aircraft engines allows you to lean them some at an idle to control fuel mixture so the plugs don't load up or start fouling during extended idle time, also you can lean the engine some when it is up to rpm to get better fuel mileage but the engine should have cylinder temp sensors with gauge so you don't over lean and burn a cylinder. When you shut the engine down with a mixture control it will shut down very smoothly and never kick back for when they kick back is when they can damage themselves internally and they will do that quite often when shutting down with mag's. Well, we are still on this poor guys thead talking about mag's so he has to be a nice guy or he would have jumped us by now.Lol

User avatar
jopete
Site Supporter - II
Site Supporter - II
Posts: 977
Joined: Mon Mar 30, 2009 8:07 am
Location: loreauville, la

Re: chasing a gremlin.....

Post by jopete » Fri Feb 05, 2016 9:02 pm

i have 2 boats, one is the gpu boat that i use a a hunting boat, and last year i bought a 12' deckover with a 300av.
the deckover i don't use much, just to ride around every now and then, but it has a lean cable on it to stop the engine. the previous owner used it every time.
i hate to use it, you run into things because of the time it take to kill the motor. i just make sure the motor has cooled down and kill it with the mags. i forget it's even on the boat.

gpu boat gets killed with the mag switch every time. motor has about 870 hrs on it. it hadn't blewup yet, but you never know. lol

Post Reply

Return to “Aircraft Power Only”