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Thread: Airboat with Lycoming O-540

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    Default Airboat with Lycoming O-540

    I have an airboat with a Lycoming engine it it. I have an over heating problem and no nothing about airplane power plants. And now with a messed up back I have no way to really work on it. So does any one know of or do work on Lycomings for a reasonable rate? Thanks for any help.

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    This is the boat with the problem:
    AB4.jpg

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    Moderator stid2677's Avatar
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    As an aircraft mechanic, I can just make a couple recommendations to check. If this setup has operated correctly in the past and is now running hot, check for an exhaust restriction and check fuel flow and make sure it is not running too lean. On an air cooled airplane engine both will cause overheating.

    Hope you get it fixed.

    Steve
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    Member ratlmn's Avatar
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    What octane fuel are you running? Also I've talked to people that put a bigger oil cooler on and relocate it to a spot that gets plenty of air circulation. Just some thoughts.....I was in the same situation as you, with that same boat many moons ago (2003).......... I finally sold it. I brought it up to the Ivishak/Echooka.........thats a whole other story. The guy I sold it to said he had a friend that was a aircraft mechanic and he was going to fix it up. I took a loss on that boat big time......ssshhhhh....don't tell my wife. I hope whoever you bought it from informed you of it's history and gave you a deal!

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    Quote Originally Posted by ratlmn View Post
    What octane fuel are you running? Also I've talked to people that put a bigger oil cooler on and relocate it to a spot that gets plenty of air circulation. Just some thoughts.....I was in the same situation as you, with that same boat many moons ago (2003).......... I finally sold it. I brought it up to the Ivishak/Echooka.........thats a whole other story. The guy I sold it to said he had a friend that was a aircraft mechanic and he was going to fix it up. I took a loss on that boat big time......ssshhhhh....don't tell my wife. I hope whoever you bought it from informed you of it's history and gave you a deal!
    Well if you are saying it was this exact same boat, then no he didn't tell me. He took me out on a short run and all seemed good. Told me he was buying a larger one (not getting rid of a problem one). I took it out and over heated 3 times before I got to my cabin. So I got towed most of the way out and only ran it up the Big-Su from the Deshka and it was hot by the time I got to the landing. So of course he never responded to my phone calls or e-mails. So if I can't get it fixed then I loose a lot of money too. Can't work due to back surgery so not a lot of money to spend on it. I know where I can get a Chevy 350/ gear box/ 6 blade but done have the ability or knowledge to swap it out.

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    Grumpy, if you went on Southernairboat.com and sign up there (free) you can go to aircraft motor forum and they will give you loads of free help, thats a popular motor for airboats and they will help you big time, I'm sure. I'm retired and have some free time, if there is anything I can do to help, send me a pm. Bud

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    Member ratlmn's Avatar
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    Grumpy, sorry to hear the guy wasn't upfront/honest with you. Like I said I'm no A&P mech. But research I did made me think If I had run the proper avgas through it, it would've run cooler, plus a bigger oil cooler. I honestly don't know. I got fed up and bought another then sold this one cheap to get it out of the yard. I actually sold it to the guy I bought the newer airboat from. Like I said above, he said his friend was an A&P and he was going to fix it up. So I don't know if the boat has been worked on since I owned it or not. Below is an ad from craigslist, one of those might bolt right up, if not maybe the guy has some knowledge of lycoming motors, It's worth a shot..............Jeff












    0470 GPU Continental 6 cylinder engine for airboat.
    New Rings
    Rebuilt Carburetor and Magneto
    more than one engine available. I put a new one on my boat this year and it made a huge difference!
    $2500 OBO
    Richard 243-4804


    Location: Anchorage
    it's NOT ok to contact this poster with services or other commercial interests

    PostingID: 2300615828

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    Thanks Jeff, I think I will e-mail him and see. I don't think the prop from the Lycoming will work on Continental but he may know of someone that can work on mine or knows of another engine. Another friend of mine just messaged me telling me to look at the same ad you posted..

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    Not having anything to do I was wondering what would cause a air cool engine to get hot. It appears the oil cooler keeps the engine cool, check the oil pump, oil filter (stop-up) anything that would keep oil from getting to the radiator. Do a compression test and check the timing, is your radiator to small, what about location?


    I also found some post on Southern airboats.


    shroud, but still have it. Remember that most of those aircrafts have shrouds and ducts that cool the engine off. If some of those vents get stuck overheating is common.


    ... cold, and then send it through the cooler when the oil gets hot. The article linked above does not say that specifically, but it suggests that an overheating problem may be caused by a leaking vernatherm allowing significant ammounts of oil to by-pass at all times. Seems to me that it would have ...


    what da i know we run both always on been running that way for over 10 years. same with the mags both run at same time. if ideling overheating problems have been told run 1 mag more advanced like 10 degree will make engine run cooler for frogging ect. that case run both mags to start then switch to your running preferance. oh boy have i started somthing now .


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    Made several phone calls today and ended up catching one of guys driving within a mile of the house so he stopped by. First thing he said is we need to get rid of the oil cooler and get a larger one along with the oil lines. Then told me the air shroud was all wrong and we need to change that. Turns out he is a friend of my brother-in-law and is willing to help me go through it and to compression checks, timing and all. Looks like it may be a couple weeks before he can get to it. So maybe I will get this thing running after all without a lot of money out of my pocket. Thanks for all your input....

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    Grumpy glad to hear it! Keep me posted I'd like to see that boat when it's running right.........Jeff

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    Good news Grumpy, I've been thinking that your problems may not be as major as you are believing. If you need a hand swinging some wrenches sometime, like I said I am retired and have the time, send me a pm. Happy to help. Bud

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    AK Grumpy Just A Thought, Sorry Don't Know Anything About Aircraft Motor But I Have Had Problems With The Over Heating On The Car Motors In The Airboats From A Lean Fuel Mixure You Might Check That To. Skip

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    I would think the "principle" would be the same as a problem I had with my truck's tranny when hauling 10,000#. The first thing I did was put a larger oil pan on the tranny. Second, I added a second oil cooler next to the first, doubling the amount of oil being cooled. Third, I went with all synthetic oil. Night and day difference for me. I have never had a Lycoming, but it seems like the concept I mention is the way you are heading. Great that someone that knows what they are doing is jumping in to help. Keep us informed how this progresses.
    "...and then Jack chopped down the beanstock, adding murder and ecological vandalism to the theft, enticement and vandalism charges already mentioned, but he got away with it and lived happily ever after without so much as a guilty twinge about what he had done. Which proves that you can be excused just about anything if you're a hero, because no one asks the inconvenient questions." Terry Pratchett's The Hogfather

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    Quote Originally Posted by akblackdawg View Post
    Good news Grumpy, I've been thinking that your problems may not be as major as you are believing. If you need a hand swinging some wrenches sometime, like I said I am retired and have the time, send me a pm. Happy to help. Bud
    Thanks Bud, I may just hit you up on that one. Being I can't be to much of a help right now. Looks like we will be doing most of the work in the Valley.

    And Jeff.. if we get her running I will get with you and take her out for a spin. But looks like when it was first built the guy did some things wrong maybe. The guy that is going to help me runs nothing but Lycoming's. So I am a little more hopeful now. He said he loves the way it is set up and will show me how to adjust prop and all.

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    Roger45.. will do.

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    I was just reviewing your original post. Back to basics...things not said...when you have an Air Cooler you need motion to blow wind over the cooler so it can work. If you are idling (not moving), air doesn't blow over the cooling fins of the oil cooler, and the oil stay hot and gets hotter. I learned this concept when I was backing a 5th wheel up on a hot summer day...my tranny temps went sky high Right Now and it was spooky. So, are you overheating when cruising, when stopped and at idle, and/or at certain RPMs/Speeds only? If you are just running it in your driveway, you might turn a blower motor onto the cooler and see if that helps or not...just another idea of something to look at. It is great to hear that you have met someone that knows these engines inside and out too! Let us know what the final outcome is.
    "...and then Jack chopped down the beanstock, adding murder and ecological vandalism to the theft, enticement and vandalism charges already mentioned, but he got away with it and lived happily ever after without so much as a guilty twinge about what he had done. Which proves that you can be excused just about anything if you're a hero, because no one asks the inconvenient questions." Terry Pratchett's The Hogfather

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    I assume by running hot you mean oil temp, not Cly head or EGT? If so, unless the boat was a day one abortion[meaning it never ran right] first thing I would do is pull a line from the input side of the cooler, stick it in a container start the engine, let it run for a timed period[say 15 secs-make sure there is plenty of oil in the engine!]. Lets say you got 2 quarts. Now pull the output cooler hose and repeat the test exactly. You should get very close to the same amount of oil. If not, the coolers plugged.

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    Quote Originally Posted by jim in anchorage View Post
    I assume by running hot you mean oil temp, not Cly head or EGT? If so, unless the boat was a day one abortion[meaning it never ran right] first thing I would do is pull a line from the input side of the cooler, stick it in a container start the engine, let it run for a timed period[say 15 secs-make sure there is plenty of oil in the engine!]. Lets say you got 2 quarts. Now pull the output cooler hose and repeat the test exactly. You should get very close to the same amount of oil. If not, the coolers plugged.
    Jim, I don't know if this boat ever ran right. And yes it is a oil temp problem. If you read through all this you see Jeff owned this same boat in '03 time frame and got rid of it because of the over heating problem. But when he sold it he told the new owner of the problem. I wasn't told of the problem. But with all that said. The guy that is going to help me runs Lycoming's. He thinks when the boat would built the wrong size oil cooler was put on the boat and the cowling is also wrong and there are a few other things missing or need to be fixed.

    And Roger, it overheats while running down the river. But I understand your thinking on overheating if sitting. If the larger cooler itself doesn't completly fix it I may put a fan on the cooler also.

  20. #20

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    Who ever is doing the wrenching should look for:
    Fuel restrictions
    Proper/Adequate/Clean fuel filter
    Baffles inbetween cylinder for proper air flow/distribution
    Proper Full Speed RPM..2750 or what ever is rated on the data tag
    Proper Manifold Pressure at full throttle...max one inch over rated RPM, if over or under, adjust or replace the prop.
    Adequate Oil Cooler Volume and Location
    Adequate Engine Shroud...just looking, looks like this one is too short but photos can be deceiving.
    Every cylinder should be within 50 degrees at the cylinder head temp locations
    Dial indicate the lift of the valves...have to pull the valve covers to do this...CRITICAL CHECK. Do it..sometimes the cam lobs wear due to improper storing and/or improper lubricating oil.
    Ignition Timing...Time both mags, IAW the the specs on the data tag.
    Change the oil filter if it has one...If not clean the oil mesh screen. At the same time, pull the oil temp thermostat and make sure it operating by putting it in boiling water.
    Make sure the Spark Plugs are the correct heat range.
    All this sounds like a lot of work but really quite easy and even a novice should be able to do it in days time.
    That is one of the best motors in the industry.
    Good Luck with it.
    "96% of all Internet Quotes are suspect and the remaining 4% are fiction."
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