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Overheating and detonation

Posted: Sun Feb 11, 2018 9:03 am
by FlounderPounder
I am new to the AV engines, I have an 0-360 on my rig, after about 30 min of running it overheats and detonates bad. Need a direction to start looking for the issue. Thanks


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Re: Overheating and detonation

Posted: Sun Feb 11, 2018 9:27 am
by GMAC 76
I would look at fuel/air or timing related...maybe the wrong carb, lean/rich lever not on full rich, intake leak, timing or mags not in sync.....had one doing that here a while back and found out that the lean rich lever was put on with no positioning pin and the engine was running terrible lean and would get very hot very fast....and of course then there is always the oil cooling system to check out

Re: Overheating and detonation

Posted: Sun Feb 11, 2018 9:37 am
by FlounderPounder
GMAC 76 wrote:I would look at fuel/air or timing related...maybe the wrong carb, lean/rich lever not on full rich, intake leak, timing or mags not in sync.....had one doing that here a while back and found out that the lean rich lever was put on with no positioning pin and the engine was running terrible lean and would get very hot very fast....and of course then there is always the oil cooling system to check out
I have made sure the rich lean lever does go to full rich, I’ve used starting fluid to check for intake leaks, can I check mag timing with a regular timing light, or do I need the dual mag light? And how do I know if I’m running the wrong carb? If so can I jet it or do I have to replace it? Thanks


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Re: Overheating and detonation

Posted: Sun Feb 11, 2018 10:33 am
by GMAC 76
just cause the l/r lever is in full rich doesn't mean the shaft in the carb is in full rich UNLESS the positioning pin is in the lever...then ya know for sure mabye...cause there is always the chance that the shaft inside the carb has twisted or broken off and the lever is doing nothing.....the 0360 uses the MA-4-5 CARB...if there is a tag on the carb read the 10-????? part number that will tell engine application...if it is a 4-5 carb it should not be too lean unless someone has modified the main jet/nozzle....the 360 is the smallest engine that uses the 4-5 carb......you will need a mag timing light to synchronize the 2 mags...depending on your flywheel if it is installed right you can check the degrees of timing with the same light using the degrees and tdc marks on the flywheel ....I have heard you can use a automotive timing light but I have never tried it and don't know how it could tell ya what degrees timing was set at...also a simple mag drop test taken at 1700 rpm may tell ya if there is a mag problem both mags should be within 100rpms at drop off

Re: Overheating and detonation

Posted: Sun Feb 11, 2018 10:39 am
by FlounderPounder
GMAC 76 wrote:just cause the l/r lever is in full rich doesn't mean the shaft in the carb is in full rich UNLESS the positioning pin is in the lever...then ya know for sure mabye...cause there is always the chance that the shaft inside the carb has twisted or broken off and the lever is doing nothing.....the 0360 uses the MA-4-5 CARB...if there is a tag on the carb read the 10-????? part number that will tell engine application...if it is a 4-5 carb it should not be too lean unless someone has modified the main jet/nozzle....the 360 is the smallest engine that uses the 4-5 carb......you will need a mag timing light to synchronize the 2 mags...depending on your flywheel if it is installed right you can check the degrees of timing with the same light using the degrees and tdc marks on the flywheel ....I have heard you can use a automotive timing light but I have never tried it and don't know how it could tell ya what degrees timing was set at...also a simple mag drop test taken at 1700 rpm may tell ya if there is a mag problem both mags should be within 100rpms at drop off
Thanks for the info, I’ll look at all that when I get back home, I’ll also be ordering a duel mag timing light to check it accurately. One more question what should the timing be set at?


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Re: Overheating and detonation

Posted: Sun Feb 11, 2018 10:45 am
by GMAC 76
25 degrees BTDC.....and keep the plug gap around .022

Re: Overheating and detonation

Posted: Sun Feb 11, 2018 10:52 am
by FlounderPounder
GMAC 76 wrote:25 degrees BTDC.....and keep the plug gap around .022
Thanks again for the info. Greatly appreciate it


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Re: Overheating and detonation

Posted: Sun Feb 11, 2018 12:16 pm
by FlounderPounder
FlounderPounder wrote:
GMAC 76 wrote:25 degrees BTDC.....and keep the plug gap around .022
Thanks again for the info. Greatly appreciate it


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The carb is a ma-4-5, 10-3479. Is that the right carb?


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Re: Overheating and detonation

Posted: Sun Feb 11, 2018 2:23 pm
by Deano
Excuse the stupid question, but . . .
You are running AV-gas, right ?

Re: Overheating and detonation

Posted: Sun Feb 11, 2018 4:34 pm
by GMAC 76
FlounderPounder wrote:
FlounderPounder wrote:
GMAC 76 wrote:25 degrees BTDC.....and keep the plug gap around .022
Thanks again for the info. Greatly appreciate it


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The carb is a ma-4-5, 10-3479. Is that the right carb?


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That carb is OEM on the 210 hp franklin engine and should work very well on the 0-360...it is especially sweet on the AV 200 so I would say the carb is good and not the issue.so now back to the lean rich and timing and as mr deano said avgas????

Re: Overheating and detonation

Posted: Sun Feb 11, 2018 4:48 pm
by FlounderPounder
GMAC 76 wrote:
FlounderPounder wrote:
FlounderPounder wrote: Thanks again for the info. Greatly appreciate it


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The carb is a ma-4-5, 10-3479. Is that the right carb?


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That carb is OEM on the 210 hp franklin engine and should work very well on the 0-360...it is especially sweet on the AV 200 so I would say the carb is good and not the issue.so now back to the lean rich and timing and as mr deano said avgas????



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Re: Overheating and detonation

Posted: Sun Feb 11, 2018 4:53 pm
by FlounderPounder
FlounderPounder wrote:
GMAC 76 wrote:
FlounderPounder wrote: The carb is a ma-4-5, 10-3479. Is that the right carb?


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That carb is OEM on the 210 hp franklin engine and should work very well on the 0-360...it is especially sweet on the AV 200 so I would say the carb is good and not the issue.so now back to the lean rich and timing and as mr deano said avgas????



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Not running av gas, can’t buy it down here without a tail number of a plane is what I was told by the local airport. My timing light won’t be in for a couple of days and it is to cold too pittle with for a couple of days


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Re: Overheating and detonation

Posted: Sun Feb 11, 2018 5:07 pm
by GMAC 76
if ya don't or cant run avgas there will be an issue with heating maybe not severe but still an issue especially if the timing and the carb are all set as if you were supposed to be running avgas....the airport where I get avgas told me the same thing...told him I don't have a plane then he said hell just put your vehicle tag number in when ya set up the credit card machine....that was 8 years ago and still pumping avgas on the tarmac...lol...I would take the time to pull the carb and split it to verify the lean rich shaft is inact and working properly inside the carb just to eliminate one more thing while your waiting for the mag lite

Re: Overheating and detonation

Posted: Sun Feb 11, 2018 5:39 pm
by mojoe
What do the plugs look like?

A clear pic of them organized by cylinder may help.

Numerous times I have seen 1 (or more) cylinder not fire which made the other cylinders work harder, get hot and detonate badly under a load.

Re: Overheating and detonation

Posted: Sun Feb 11, 2018 5:48 pm
by FlounderPounder
mojoe wrote:What do the plugs look like?

A clear pic of them organized by cylinder may help.

Numerous times I have seen 1 (or more) cylinder not fire which made the other cylinders work harder, get hot and detonate badly under a load.
I will pull them and take a picture, and get back with y’all.


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Re: Overheating and detonation

Posted: Sun Feb 11, 2018 5:49 pm
by FlounderPounder
GMAC 76 wrote:if ya don't or cant run avgas there will be an issue with heating maybe not severe but still an issue especially if the timing and the carb are all set as if you were supposed to be running avgas....the airport where I get avgas told me the same thing...told him I don't have a plane then he said hell just put your vehicle tag number in when ya set up the credit card machine....that was 8 years ago and still pumping avgas on the tarmac...lol...I would take the time to pull the carb and split it to verify the lean rich shaft is inact and working properly inside the carb just to eliminate one more thing while your waiting for the mag lite
I sure will thanks again


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Re: Overheating and detonation

Posted: Sun Feb 11, 2018 9:59 pm
by Slidin Gator
Assumption #1: You just got the boat from some one and don't know more.
Assumption #2: The motor is mechanically sound (valves, etc.)
Assumption #3: It's an aircraft motor, so it was set up to run on AV Gas (see #1).
Assumption #4: You are running 93 Octane pump gas with ethanol
Assumption #5: Motor runs great until it heats up.
Assumption #6: You have a standard compression motor - see below.
Unknown: Where is "Down Here"? When they ask for tail numbers, just give them the vessel registration.

Take an engine that is tuned for and running great on 100 LL AV Gas. Now fill it with 93 Octane pump gas.

That motor will start better and run better when cold. But, the hotter it get's the worse it runs. Once it starts detonating it just heats up even more, leading to more detonation. Generally speaking, you need to either increase your octane or reduce the timing advance to the point that eliminates your detonation issues. Once the detonation issues are resolved, if you think the motor is still running hot please post the data.

Rich running motors will run cooler but will foul plugs. Lean running motors run hot and burn exhaust valves. Detonating motors just blow up.

Not knowing the mechanical compression ratio of the engine makes it hard to advise. Do you know what pistons are in the motor? Otherwise a standard automotive compression test result for all cylinders would be helpful to decipher.

The first and easiest test is filling it with AV gas and try it. Short of that, find the best fuel you can (93 supreme or 90 no ethanol) and add Octane boost with lead substitute. See if any of that changes things. During this test you can test your mags separately to see if there is an issue with timing match. Run on one mag at a time to see how the operating temps and performance changes.

Depending on the above findings, you may need to back off your timing, 20 degrees BTC would be my next try.

If your are new to AV motors, the timing procedure will be all new to you, unless you are a 1950's points ignition guy. I can post/send you a slide show with info on setting timing if needed.

Plan to run lead substitute full time if nothing else. Those exhaust valves really need something!

Re: Overheating and detonation

Posted: Mon Feb 12, 2018 7:35 am
by Striker543
BND Automotive makes ACES IV octane booster. Not cheap, but works great. You have to call them to order it because they don’t make sales available online.

Re: Overheating and detonation

Posted: Mon Feb 12, 2018 8:44 am
by FlounderPounder
Slidin Gator wrote:Assumption #1: You just got the boat from some one and don't know more.
Assumption #2: The motor is mechanically sound (valves, etc.)
Assumption #3: It's an aircraft motor, so it was set up to run on AV Gas (see #1).
Assumption #4: You are running 93 Octane pump gas with ethanol
Assumption #5: Motor runs great until it heats up.
Assumption #6: You have a standard compression motor - see below.
Unknown: Where is "Down Here"? When they ask for tail numbers, just give them the vessel registration.

Take an engine that is tuned for and running great on 100 LL AV Gas. Now fill it with 93 Octane pump gas.

That motor will start better and run better when cold. But, the hotter it get's the worse it runs. Once it starts detonating it just heats up even more, leading to more detonation. Generally speaking, you need to either increase your octane or reduce the timing advance to the point that eliminates your detonation issues. Once the detonation issues are resolved, if you think the motor is still running hot please post the data.

Rich running motors will run cooler but will foul plugs. Lean running motors run hot and burn exhaust valves. Detonating motors just blow up.

Not knowing the mechanical compression ratio of the engine makes it hard to advise. Do you know what pistons are in the motor? Otherwise a standard automotive compression test result for all cylinders would be helpful to decipher.

The first and easiest test is filling it with AV gas and try it. Short of that, find the best fuel you can (93 supreme or 90 no ethanol) and add Octane boost with lead substitute. See if any of that changes things. During this test you can test your mags separately to see if there is an issue with timing match. Run on one mag at a time to see how the operating temps and performance changes.

Depending on the above findings, you may need to back off your timing, 20 degrees BTC would be my next try.

If your are new to AV motors, the timing procedure will be all new to you, unless you are a 1950's points ignition guy. I can post/send you a slide show with info on setting timing if needed.

Plan to run lead substitute full time if nothing else. Those exhaust valves really need something!
I live in Victoria TX. The boat it self I have owned it’s whole life. The air setup I just bought from a buddy of mine who had the engine gone through about 2 years ago. He quit using it and went to a different setup. As soon as the whether warms up I’m going too go through all the normal checks and will post what I come out with, for further advice. This sounds stupid but I’ve been a mechanic in the oilfield for 20 yrs, but I just like too know a little info before I proceed. Thank y’all for the help and guidance this is the first av engine I’ve worked on.


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Re: Overheating and detonation

Posted: Mon Feb 12, 2018 10:28 am
by FlounderPounder
Slidin Gator wrote:Assumption #1: You just got the boat from some one and don't know more.
Assumption #2: The motor is mechanically sound (valves, etc.)
Assumption #3: It's an aircraft motor, so it was set up to run on AV Gas (see #1).
Assumption #4: You are running 93 Octane pump gas with ethanol
Assumption #5: Motor runs great until it heats up.
Assumption #6: You have a standard compression motor - see below.
Unknown: Where is "Down Here"? When they ask for tail numbers, just give them the vessel registration.

Take an engine that is tuned for and running great on 100 LL AV Gas. Now fill it with 93 Octane pump gas.

That motor will start better and run better when cold. But, the hotter it get's the worse it runs. Once it starts detonating it just heats up even more, leading to more detonation. Generally speaking, you need to either increase your octane or reduce the timing advance to the point that eliminates your detonation issues. Once the detonation issues are resolved, if you think the motor is still running hot please post the data.

Rich running motors will run cooler but will foul plugs. Lean running motors run hot and burn exhaust valves. Detonating motors just blow up.

Not knowing the mechanical compression ratio of the engine makes it hard to advise. Do you know what pistons are in the motor? Otherwise a standard automotive compression test result for all cylinders would be helpful to decipher.

The first and easiest test is filling it with AV gas and try it. Short of that, find the best fuel you can (93 supreme or 90 no ethanol) and add Octane boost with lead substitute. See if any of that changes things. During this test you can test your mags separately to see if there is an issue with timing match. Run on one mag at a time to see how the operating temps and performance changes.

Depending on the above findings, you may need to back off your timing, 20 degrees BTC would be my next try.

If your are new to AV motors, the timing procedure will be all new to you, unless you are a 1950's points ignition guy. I can post/send you a slide show with info on setting timing if needed.

Plan to run lead substitute full time if nothing else. Those exhaust valves really need something!
All the information, pics, videos, literature you can spare is greatly appreciated.


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Re: Overheating and detonation

Posted: Mon Feb 12, 2018 11:19 am
by John Fenner
FWC has 3 new o540 diamondback boats, they run car gas only, they were doing the same as you describe, they had the timing backed down to 20° and no more problem.

Re: Overheating and detonation

Posted: Mon Feb 12, 2018 11:34 am
by FlounderPounder
John Fenner wrote:FWC has 3 new o540 diamondback boats, they run car gas only, they were doing the same as you describe, they had the timing backed down to 20° and no more problem.
Cool thanks


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Re: Overheating and detonation

Posted: Mon Feb 12, 2018 3:55 pm
by Deano
FlounderPounder wrote: All the information, pics, videos, literature you can spare is greatly appreciated.
Flounder, Go to this link. There is enough info there that you will find more than a little bit that will help your cause.
http://www.southernairboat.com/pdf/airc ... oming/360/

After you are in that directory:
Double (left) click a link --> will open the file. You can download it from inside the pdf viewer.
-or-
right click the link, and then select Save Link as to save a local copy

Re: Overheating and detonation

Posted: Mon Feb 12, 2018 9:51 pm
by Slidin Gator
Flounder,
I was in the same boat as you a couple years ago, with my first AV motor. So I have been through this (and other) learning curves. I am attaching some documents that were useful to me. The timing box is useful to check the timing by yourself, otherwise you need 2 feeler gauges and a helper to move the prop.

Before doing anything on the motor, I still recommend finding a tank of 100 LL to run through the motor. If that solves the problem you will know you are on the right track here. In any case it will give you a comparison point to consider the change in performance once you get the motor tuned for pump gas.

Lycoming used 7.2 and 8.5 compression ratio pistons in the straight valve engines. Angle valve engines had 8.5 or 8.7. Higher compression ratio after market pistons are available. Lycoming rates the 7.2 for use on 80-87 octane fuel. The 8.5 is rated for 91-96 Octane and the higher compression ratio’s require 100 LL fuel. Keep in mind that Automotive fuel burns faster than Aviation fuel, backing off the timing from 25 to 20 roughly compensates for the quicker burn of auto fuel. Since Airboat engines in the South tend to run hot, I would err on the safe side of these ratings.

If the engine still has issues on 100 LL fuel, you need to check the timing and confirm that both mags are firing at the same time. If the mag timing is staggered the engine would have issues such as you describe. The mags fire when the points open. You can check this with a set of thin feeler gauges (or a business card etc.) under each point. Have someone turn the prop slowly (pull plugs to release compression first). When the points open the feeler gauges will pull free. The Timing box information attached is for a unit you can buy from aviation supply houses for about $50. With this box you can check and adjust the timing by yourself.

I suspect that the FWC boats are running low compression 540 engines to run on pump fuel. Perhaps this is why the FWC officer that gave me a safety inspection last month was stuck in his new Diamondback afterwards. He had to make the trainee get off and wiggle the grass rake to get going on dry ground.

Look at this link for details on timing, as well as Youtube for video's:
https://www.avweb.com/news/maint/184370-1.html

Re: Overheating and detonation

Posted: Tue Feb 13, 2018 7:55 am
by terrible ted
[quote="FlounderPounder"][quote="Slidin Gator"]Assumption #1: You just got the boat from some one and don't know more.
Assumption #2: The motor is mechanically sound (valves, etc.)
Assumption #3: It's an aircraft motor, so it was set up to run on AV Gas (see #1).
Assumption #4: You are running 93 Octane pump gas with ethanol
Assumption #5: Motor runs great until it heats up.
Assumption #6: You have a standard compression motor - see below.
Unknown: Where is "Down Here"? When they ask for tail numbers, just give them the vessel registration.

Take an engine that is tuned for and running great on 100 LL AV Gas. Now fill it with 93 Octane pump gas.

That motor will start better and run better when cold. But, the hotter it get's the worse it runs. Once it starts detonating it just heats up even more, leading to more detonation. Generally speaking, you need to either increase your octane or reduce the timing advance to the point that eliminates your detonation issues. Once the detonation issues are resolved, if you think the motor is still running hot please post the data.



I will say 93 is to low add octane. There is other components to av gas that make it run cooler that you can not get in mogas. You will need to add lead, I know some also add marvel mystery oil to there tank. The fuel is made for running at low rpms

here read this http://www.dragracingpinoy.com/articles ... racing-gas