i got all my parts for the belt drive and my new razor x prop. they don't make the whirlwind mini prop any more or the composite hub. got it all together and set my pitch on prop which is a little tricky. no level spot on prop 3 in from tip so i used a strait edge and digital level and set both blades the same 12 degrees. took it out and i couldn't believe the difference in the razor prop and the ultra. the razor was unbelievably quiet. the ultra sound was like a swarm of bees. the push was great and as soon as i pushed it wide open it was on plane. now to the bad part. i took my son out for some flounder gigging and and boat performed great until we started to stop and it backfired and died sound like a shot gun. well i tried to start it and it would start and backfire every time i tried to give a little gas and die again. we did this over and over again until we got back to ramp. at least we didn't have to paddle a mile. the backfiring blew one of my exhaust off and the excessive cranking burned up the starter and chipped a tooth on the starter clutch. i had 3 mags which 2 are brand new that i can't get to fire and 1 will only fire on 3 cylinders. not giving up so i ordered a new mag a new starter and a new solex carburetor. going to start fresh and beat this thing of bad luck.
https://www.youtube.com/watch?v=rhv4RpPmqU8

Any chance the Distributor, if it has one , came loose ?
It sounds like a timing thing to me or the carb got a piece of
Dirt in it and is FLODING a lot...

its the 4a084 engine and the mag was shorting out. i put a used one on and it ran ok but had a skip on no 3 cylinder. just put a new set of spark plugs in and no spark to plug from wire. also my starter wasn't burned up as i thought the battery was dead from leaving the front led light on. now i'll have a spare starter. i used to carry one on the old airboat just in case. it was a 350 chevy.

it is nice to know that the razor prop is a lot quieter. i will have to keep that in mind, as i still am looking for things to get for my 084 motor. thats the fun with having two different styles of drives, my cuyuna with the gear box is one direction, and the 084 is the other.
picked up a 3/4" aluminum plate today for a good price. slowly starting to get things together for making my own redrive for the 084
hope you get that back fire figured out. do you have a burned valve or was it the timing?

the mag was a couple months old but it was cross firing some how. i put the used one on and misfires on one cylinder but will rev up which the other mag would only rev to maybe 1200 and then backfire. i think a new mag will fix the engine problem. i drilled out the idle jet a little too much and fouled out the plugs and that didn't help.

just wonder if there is some carbon tracking on the magneto cap? which would send the spark to the weakest link

It looks like it jumped up on plane quickly...Nice, I'd be happy with that too...I know Aerokirk was experimenting with changing the whirlwind prop pitch a little it makes me wonder where he ended up setting his...I hope you get it straightened out for some uneventful fun time.. I think you're just about there..
Nice video what a great area to travel around !!!;thumb;

Right now I'm set at 10 degrees (measured 3" in from the tips on the flat side). That's running the 084 with a Circle-S reducer. I'm happy with the thrust and top end rpms at that setting.

Ted

well that got me thinking when my razor was set at 12 degrees i could only turn 3300 rpm wide open when the engine was running good maybe i misread my digital level. i dropped it down to 8 degree and could turn 3900 rpm. i set it down because it didn't sound like it was turning a lot of rpm and my son was going with me and i thought i needed more push at low end. it ran great and got on plane with both of us an ran 26 mph so i was happy until the mag shorted and it started back firing and ruint our night. just got the new mag and in process of installing it. back to the pitch i'm not sure any of my readings were correct. i'm using a cheep foreign made one' it has a measuring surface of about 2 1/4 in and i can slide it up or down on the prop 3 inches from the tip and get a different reading.thats why i used a straight edge across the tip of the prop on top of the leading edge to the bottom of the prop and got my measurements and made sure the prop was sitting horizontal with face of prop strait up and down.

I bought a craftsman digital level with a few different settings and it's tough getting the readings exact from one blade to the next...Same deal for me just measure in from the tip and get both the same...If anything the craftsman is too accurate and I'm adjusting down to 10ths of a degree....I guess it's not really how accurate the given reading is...It's more a matter of using the same technique/tool each time then adjust the pitch into the range you're looking for...

exactly corky.the reading doesn't really matter just so both are the same and prop is in same place mean on the same side of engine when checked. mine would give me a different reading from one side of boat to the other. all my readings were on the right side of boat with leading edge pointing up.

Keep at it, they all have bugs to work out before the enjoyment comes. They are a really reliable engine once you get it all figured out.

yes it is a good little engine. just got the new mag on and after adding a little oil to carburetor to get the compression back up it cranked up and runs like it's supposed to. now to find time to run it.

just talked to marty bray and he said my new boat would be ready in 2 weeks. now that i got this engine straightened out it time to invest in a new 116 airboat hull.

it would be fun to run across one of hulls here in Alaska. they look like they are well put together

Nice...Any custom colors on the hull ??? Make sure to take some pics so we can all be jealous...:lol:

no just plain old grey.

You'll be glad you picked a Marty Bray hull ... he does great work! They scoot through the water good and are totally controllable. If you're rudders are designed right you'll find that you can turn 360's in the length of the boat, it just pivots around the center. Very handy when you get yourself in a tight spot.

aerokirk your build sold me on the 116 mini pro. the way your's run was just what i was looking for. plenty of power and i can't say enough about the razor x. it a great and quiet prop just like my whisper tip. they look almost identical except the whisper tip is a lot bigger.

You'll be glad you picked a Marty Bray hull ... he does great work! They scoot through the water good and are totally controllable. If you're rudders are designed right you'll find that you can turn 360's in the length of the boat, it just pivots around the center. Very handy when you get yourself in a tight spot.

Like this? Someone questioned my rudder setup so I had to record this.

https://youtu.be/PZQZbKgMf0Y

thats turning so sharp its almost backing up

i got the boat saturday and very happy how it looks. 11 ft long 70 inches at the bottom 77 across top 18 in transom with nice deck with storage and lid and 12 inch stringers. 220 lb. my son and i picked it up and sat it on the trailer.

Very nice...He makes a good hull...You should start a build thread for that hull so we can watch you put it together....;thumb;

well not much of a build. going to set everything off my old boat and install it on this one cage, seat stand and eng stand and use it while there is still some good gigging goin on and build everything this winter when it slows down. the fishing gets better in the winter but gigging is best in summer. maybe i had better say when i get around to it. marty is a nice guy and puts out a fine boat. he will do what makes you happy. no complaints here except my gps took the wrong route to his shop and i passed his shop before i realized dang that guy has a lot of boats in his yard. that was his shop i passed. 2100 for boat and 100 for two single seats. i'm happy as a pig eating a bucket of slop

looks good, it would be fun to get one of those hulls, but I'm afraid i would be paying double that when the shipping is added on. but i can see a wider boat hull in the future. have fun and enjoy getting your boat going.

thanks corky and bart. only the 2nd new airboat i've owned. first one cost 800 dollars. i thought that was too high for just a hull but you get what you pay for. this hull is a lot better with composit stringers no replacing them down the road. going to have to build a platform for the engine and seat stand to set on and strong enough it will hold the thrust and weight. my old stringers were 21in and these are 36 outside center to center and inner are 12 in. not much of a deal using conduit for frame since this will not be permanent. i've got too old to work outside more than an hour and rest 10 minutes so this might take more time than getting the bugs out of the engine. i bought a new carburetor when the mag acted up and not sure if it was the mag all the time or the carburetor. it just runs much smoother than before all through the rpm range.