I am getting the bits together to build my first airboat. i had an old os max-s 30 engine that is going to run this thing i have been reading alot of posts on here and bought an 10/6 prop but it is to thick to allow the prop nut on? Now the questions, have i bought the wrong type of prop? it is plastic do i sand it down? do the letters face away from the engine? just wanted to bench test it before i go any further.

Thanks

Not really sure what part of the prop you are referring to . But , if its the inside diameter of the hub , then , simply ream it out .
And as far as the lettering ... this all depends on whether you are using a PUSHER , or TRACTOR ( puller ) prop .
Puller ( tractor ) goes facing AWAY from the engine , whereas the PULLER , has the lettering FACING the engine .
Hope this helped .
And to tell if you have a puller , or pusher , look at the way of the rotation . Counter , when lettering is facing you , is a PULLER ( tractor ) , and clockwise when facing you , then its a PUSHER . ( remember , engines rotation ( unless rare , or modified and changed ) will be COUNTER rotating

Typo:

Turbo bob wrote:
should be:

Puller ( tractor ) goes facing AWAY from the engine , whereas the PUSHER , has the lettering FACING the engine.

Fingers sometimes work faster than the brain.

what make is the prop ,sounds like its too big to me what prop do they suggest for the engine in the manual?.id say 10x6 is more for a 40 size maybe try a 9 x6.heres some.
[link]http://www.sussex-model-centre.co.uk/shopexd.asp?id=1284[/link]

Hi there it is a puller graupner standard airplane prop. The shaft is the right size just not enough thread to get the nut on the end. will a 9/6 be any thinner?

ok on closer inspection it looks as if someone has cut off some of the crank thread at some point thus now not being long enough going to try filing the prop down and see how that works out.

dont file the prop down mate it will seriously weaken it and make it dangerous.far better to get a new crank or better still another engine there are lots of engines out there for good money especially on ebay.i got an sc 61 for £25 on ebay pristine condition too.ive bought engines for a tenner on ebay before now and all of them have been good engines.some came with a prop too.
heres a cpl available now last one has wooden prop a big no no on an air boat!!.
[link]http://cgi.ebay.co.uk/JBA-61-Two-Stroke-Aircraft-Engine-NEW-99p-Start-NR_W0QQitemZ300063687610QQihZ020QQcategoryZ34055QQ rdZ1QQcmdZViewItem[/link]


[link]http://cgi.ebay.co.uk/OS40LA-BLUE-MODEL-GLOW-ENGINE_W0QQitemZ220065728844QQihZ012QQcategoryZ340 55QQrdZ1QQcmdZViewItem[/link]

[link]http://cgi.ebay.co.uk/SUPER-TIGRE-S-40-R-C-MODEL-AERO-ENGINE_W0QQitemZ160067605456QQihZ006QQcategoryZ340 55QQrdZ1QQcmdZViewItem[/link]

Do you know anyone that has a lathe? I had a shoulder nut made for one of my projects one time. Basically what you would do is ream the prop hole out bigger and make an elongated nut that will screw onto the threads yet stick past the prop. does this make sense?

I'll find it and post a pic.

Here are the pics.

A APC 9x6 or MAS 9x6 works real good with that motor
i have one of these os max 30 bushing motors, it runs great for a oldie
Also the 9x6 has a thinner shank area than a 10x6 apc or mas props

i think if he gets a 9x6 it will fit no problem after all who ever had the engine before had a prop on there at some time!!.they are quite a bit thinner than a 10x6 prop as you say.

thanks for the replies guys i will get a 9x6 and see, if not i haven't got access to a lathe but i work in the auto industry so might be able to find something like that nut that i can get to fit. The engine was given to me by an old neighbor about 10 years ago, he was running it in a stock car, so that might be why he cut it down? The engine has great compression so i am interested to see how it runs.

hello martini,iniofun1 you spend too much time on that ebay, lol i have a couple of plans that you may like ?
catch me on msn and i will pass them to ya (not air boat)

Rick your a good one to talk about spending too much time on ebay lol.

Hi the 9x6 was the same result so i am going to work on the threaded bolt idea. Just as a side note i also have a irvine 40 marine engine will this stay cool enough if i ran this instead?

unless you pump cooling water to the head, i doubt the marine motor will last long.

Whilst looking at the marine engine i noticed the nut holding the flywheel on was the same thread so i put that on which had enough thread to hold the prop but as i tightend it the engine locked up. Behind the prop flywheel was a plastic washer which was stoping the flywheel going back fully. I took this off put the flywheel and prop on and have now got it started . There did seem to be fuel leaking out from behind the flywheel though?