aerokirk's build

[eskimoboy]

That's awesome Papee will do. Thanks Aerokirk for coming up with the design.

[Papee]

AK it looks like you made a bracket to attach from that piece to the carb bolt to steady the intake?

[aerokirk]

Yes ... I edited my prior post with the bracket pictures to explain that piece ... it's just a 1/8' x 1" steel strap twisted 90 deg and fastening to the front carb stud.

[Doozit20]

Wellllll??? How she running? Need more pitch?

[aerokirk]

My initial run was on the trailer behind my 4-wheeler and it started right up. The idle was a bit rough because the electric choke was slow to heat up and stayed on full for several minutes. I reached back and pulled it off and it idled just fine. The accelerator pump works great and there is no hesitation with throttle changes. I didn't see any appreciable gain in top end rpm from that of the stock carb but that's static rpm so it's hard to tell if I'll get more hp or not until I get it on the water. I'll have to do some research on the electric choke to see if it's adjustable. I'm hoping to get it on the water sometime this afternoon if the rain stops. I really like the look of the new carb with the chrome air filter on top ... it makes it look like a bigger engine.

Update: Water run (solo) went well with smooth acceleration throughout the speed ranges. Right now I'm thinking conservatively 200 more rpm at WOT. Didn't have my GPS on board so not sure if I'm getting any more speed but it seems to cruise nicely at 2600 rpm where before it took 2800 rpm. Next I'll have to try it with a passenger. Can't justify putting more pitch in the prop though... maxing out at 3300 rpm and I know that my tach is reading high. I've found that taking pitch out to get more top end rpm negatively affects cruise settings so I'm leaving it where it is.

[Papee]

The choke is adjustable, you just loosen the three screws where the choke wire goes in or the screw on the choke arm. That screw is for choke adjustment not for idle. The idle screw is the big one on the side.

[eskimoboy]

where's the video?????

[eskimoboy]

I think were all getting real anxious right about now!

[Doozit20]

Ok so there was a definate improvement even if just with ease and smoothness of acceleration. You may be able to play with jetting. Ive read the "ron and robins build" thread and he did some different jetting to improve with head temps and such. Just a thought.

and yes a video will be awesome. Quick question.....can she run dry from a stand still???

[Papee]

Did you take note to your temp difference? I'm sure your mufflers are also holding it back some. Are you running now with the carb out of the box with no adjustments? You may get another 100-200 rpm out of adjustments but won't see the capabilities unless you let some of that exhaust loose.

Edit: I noticed you also chose to go with the chrome filter. You may also want to run with no filter on to see if it is limiting air intake and messing with the results.

[aerokirk]

O.K. fellas... you wanted a video so here it is ....

http://youtu.be/YKDiVMSJZBU

[Papee]

These carbs sure do make these engines run smooth that alone is worth the switch. Then there's the no more banging on the stock carb because the float is either stuck open or closed. Gloves and jacket already, we're soon going to be into that here but I don't mind because the fishing really picks up until its time to put the boat away for the winter.

[Doozit20]

Carb looks like its working great. I really like that air filter. One thing I will say though is please be careful turning sharp like that at low speeds. Airboats tend to sink fast if you dip that back corner with a open hull like that. You came real close towards the end of the video. Just the worrier in me. I dont want to hear about anyone diving for there airboat.

Anyways that thing really takes off when you hit the gas with what seems like little to no hesitation. Great job.

[aerokirk]

Thanks for all the observations guys! Papee ... I'm not sure that the mufflers are causing any undue back pressure because they are the flow through type. If you look in the end theres at least a one inch opening straight through to the other end. There's just a series of tiny scoops that protrude into the main channel to slow the airflow. That and the fact that there's one muffler for each two cylinders so there's not as much exhaust flow through each. I think the way I'll get my answer is by drilling a small hole upstream of the mufflers and inserting a manometer to measure pressure. The manual calls for a maximum of 20" of water column. You're right about oil temp ... it is lower with the new carb, however cylinder head temp is still higher than what I'd like to see. There doesn't seem to be a change with the new carb ... still running 475 - 500 deg at WOT. I think you're right Doozit, I'll have to look into different jetting. Papee ... any idea what adjustments are possible on the Solex short of changing jets? Are those two side screws adjustable or are they just caps for the jets?

Thanks for the concern Steve ... I like to take things (as the pilots say) right to the edge of the envelope, but I'm not usually so daring especially with a passenger. I've run it enough now that I know where the limits are, and yes, that's getting pretty close. There's pretty much nothing but deep water up here

[aerokirk]

Eskimoboy ... Have you had any issues with the idler on your Circle-S re-drive? I'm finding that if I adjust it to ride the belt it hammers the adjustment screw ... really sounds bad, so I keep it backed off but i'm getting strange sounds from the belt as though it's jumping teeth.

I think Bruce is designing a new idler that is held captive to the adjustment screw in order to stop the hammering. I'm not sure where he is with that design but I think that would help a lot.

How has yours been running?

[eskimoboy]

Mine was doing the same thing because the 2 nuts came loose so I screwed in the bolt to put a bit of tension on the belt and turned in the first nut snug and then screwed in the second nut and tighten down really hard to lock the 2 together. And it is still going strong and I don't hear and out of the way noises. With my stock carb at idle the engine doesn't idle well it has a tendancy to rev up and down, don't know if my disposable gas line filter is dirty or my carb needs cleaning. I would say I have burnt about 300 gallons of gas in this engine so far without any problem except for wanting more horses in windy conditions and carrying a second person. My brother-in-law is doing a build similar to ours but he has my old vbelt drive. I gave him my hull to use as a mold and told him to extend the boat an extra 2 feet to see if that would help the boat to stay up on plane in windy conditions and having a second person on board. Papee seems to be running just fine with his longer hull. Ill have to wait and see until my brother-in-laws build is complete before I decide if I will extend my hull, but it does seem to be the way to go.

[aerokirk]

So then how much idler pressure are you putting on your belt?

[eskimoboy]

I tighten the bolt enough until the noise went away it took a couple of tries.

[eskimoboy]

Ted are you on fb because my newphew took a video while I had it running yesterday you can watch it there.

[aerokirk]

Nick ... I Pm'd you