Newbie with Lycoming questions

[Canuk]

I recently picked up 14' Aircat with a 180 hp Lycoming engine that I plan to use in northern Ontario during ice freeze up. Other than this great site I am discovering there is not much technical information available for this engine and would appreciate some tips from you folks with more experience.

Here goes a few:

What is the propeller hub torque spec?

The past owner used NGK A8 spark plugs, is this the correct plug, what is the plug gap spec.

The old plugs are black and sooty looking, this indicates to me that the engine is running rich. It uses a 2 barrel Holley carb. Are there resources available to advise on how to begin leaning the mixture...ie re-carb or re-jet.

Appreciate any input.

 

[scottginfla]

i am no expert but here goes

prop hub torque about 45 lbs

plug gap between 18-21 (champion d-21 or d-18 plug)

its ok to run the engine on the rich side, if you want to lean it out you can re-jet the holley, not sure what size holley you have but the 500 come stock with a 72 or 73 jet, there will be two of them located in the fuel bowl, take off the fuel line and remove the four bolts that hold on the bowl, the jets willl be on the bottom on each side if the carb, flat screw driver to remove, available from any speed shop local or online, start by going down two sizes.

you could also go to aircraft carb which in my opinion would be the best thing to do, that way you can use the lean/rich cable to shut down the engine rather than using the magnito switches.

some others will chime in here also, like i said no expert here.

 

[Moritz]

IF it is a wood prop you need to tighten to 25 ft # to 40 but you need to track it. To do that tack a stick you stirr paint or ruler with & clamp it to the cage or the boat so it jus touches the tp. Rotate the prop 180 degrees & check thee clearance on the same spot as on the first tip. Need to get them with in 1/32" . You do that by tightening a little more ont one side tha other. You check the run out as you tighten the bolts up. I tighten up 1/8 of a turn going back & forth. Not going around the bolts in a circle. You want to put the prop up even.

 

[dblj006]

How about some pics? I'd like to see that old aircat. Also I'd like to see the carb setup on that old timer.

As far as torque, you can go direct to Sensenich and look them up.
http://www.sensenichprop.com/sen_html/airboat/airboat-wood-cf-rev-orig.pdf

 

[Canuk]

Thanks for the info, I am unable to obtain the 1/32" run out spec at the tip of the prop, the closest I was able to get was 3/16" - 1/4".
The prob, hub and flywheel are all clean and appear to be in good condition. I tried rotating the prop on the hub (one hole at a time) and it doesn't change so I am assuming the differential is being caused by the prop itself.

Is there a suggested method of removing material from the back of the prop (sand it?) to bring it into spec. I can see that a few thousands difference at the hub would make a big difference at the prop tip.

I will try to post a few pics of the unit and the carb.
The intake manifold has " For Air Boats Only" stamped into the casting, is this typical?
I have been shutting it off by turning off the fuel just in front of the carb and waiting for it to starve.
Are aircraft carb's readily available for this? I guess I would also have to ensure the manifold can accept it or change out both. Maybe the pics will help determine this.


Thanks for your great tips, I can sure see the passion for the sport throughout the posts and look forward to learning as much as I can from everyones experience.

 

[Canuk]

How about some pics? I'd like to see that old aircat. Also I'd like to see the carb setup on that old timer.

As far as torque, you can go direct to Sensenich and look them up.
http://www.sensenichprop.com/sen_html/airboat/airboat-wood-cf-rev-orig.pdf

Thanks for the tips, I managed to get the run out into spec by sanding and refinishing the inside of the prop. Removing approx .030 of wood and applying 3 extra coats of varnish on the low side did the trick. Proper???

I have been trying to figure out how to post a couple of pics without success. Based on what I have read it appears the pic must be on a public web site that a URL can point to, how are you folks doing this this?

 

[FP1201]

How about some pics? I'd like to see that old aircat. Also I'd like to see the carb setup on that old timer.

As far as torque, you can go direct to Sensenich and look them up.
http://www.sensenichprop.com/sen_html/airboat/airboat-wood-cf-rev-orig.pdf

Thanks for the tips, I managed to get the run out into spec by sanding and refinishing the inside of the prop. Removing approx .030 of wood and applying 3 extra coats of varnish on the low side did the trick. Proper???

I have been trying to figure out how to post a couple of pics without success. Based on what I have read it appears the pic must be on a public web site that a URL can point to, how are you folks doing this this?

You can up-load your pictures to thi web site, just click on the "Pictures & Wallpapers" link at the top. Here's the tricky part to posting photos:
click on the picture you're viewing, so it's full sized and not a "thumbnail"
Now "right click" the mouse button and a box will appear. at the bottom, select "properties" and another box will open.
About the middle you'll see a hyperlink address like this one: http://www.southernairboat.com/photopos ... me_002.jpg
Drag the mouse over to highlite then copy it. This IS the address needed for pictures. 8)

BTW: I answered your other question, but didn't realize that your engine had been converted, so making a shield will be easy.
I run NKG A6 plugs and they work great! A9's are the coldest and usually run in vintage snowmobiles, A8's are for sleds that are prone to fouling, if it were mine I would run the A6 especially in cold weather unless it's really running hard then maby the A7's for the price of the plugs, experimenting isn't a financial hardship.

From what I've gathered, NGK plugs were DESIGNED for use in air-cooled, magneito fired engines having the hell run out of them, everything else is for car motors.