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Four stroke engine for air boat

Old 11-25-2003, 04:43 PM
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yamraptor2cool
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Default Four stroke engine for air boat

Does anybody have a four stroke engine on there air boat? If so what kind. Are they worth the price. I am putting it on about a 41 in. boogy board air boat that I made.


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Old 11-25-2003, 07:42 PM
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Kmot
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Default RE: Four stroke engine for air boat

Four stroke engines don't make much rpm and so to make up for it have lots of torque to swing a big prop. Unless you have lots of room for a large diamter prop you might want to reconsider using a four stroke. My $.02
Old 11-27-2003, 09:18 AM
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rsieminski
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Default RE: Four stroke engine for air boat

You could use a 3 or 4 bladed prop to cut down on the diameter, but a 2 stroke would prob be better. If you're going to buy one for this application, just get an inexpensive 2 stroke. Ya don't need a Rossi to have fun with an airboat.
Old 11-27-2003, 09:36 AM
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Default RE: Four stroke engine for air boat

YAMBLASTER ,
I have a local buddy that is running a 4 stroker and in my opinion , it is not worth it . For what the engine is , and the price he paid , I would say , either go with a regular gasser ( weedie engine ) or a 2 cycle nitro ( pending on the size of the hull you plan on using ) .
It just doesn't seem to have the "umph" to it , or enough power .
But , this is just my $0.02
If you have one already , or came across one REAL cheap , then yes , by all means - go for it , but if this is something you will have to buy new , or used and are going to pay a "normal" price , I would suggest you look down the road for a weedie or 2 cycle nitro .
Old 11-28-2003, 07:56 PM
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yamraptor2cool
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Default RE: Four stroke engine for air boat

Thanks, im not going to get a four stroke any more. I decided on a O.S. .50 SX Ringed. Your info was very helpfull.
Old 11-28-2003, 08:52 PM
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TERBObob
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Default RE: Four stroke engine for air boat

SUPER !
Now , please keep us posted and also , if possible , post some pics of her when she's finished , or even thru the phases of getting her ready .
( I know I love to see them )
Old 11-29-2003, 12:47 AM
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rsieminski
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Default RE: Four stroke engine for air boat

yamblaster2cool,
For that kind of money you could almost get a ROSSI .53. In a completely different class.

Check out the Mag .52. Less expensive, and prob a stronger engine. True ABC, not ABN.

Not that you wont be happy with the OS, you prob will be, but I just think they are overpriced.
Old 11-29-2003, 09:56 AM
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Default RE: Four stroke engine for air boat

You might also want to check out the MDS engines from Russia. I have the .18 and .40. Very strong engines for the price. I have the .18 on my Swamp Buggy, which is not a light hull, and it moves it along very well. I have the .40 mounted on my Air Force which is a light hull and it litteraly flys. Hard to keep it on the water.
Old 11-29-2003, 11:31 AM
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yamraptor2cool
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Default RE: Four stroke engine for air boat

Hi, I just checked out Horizon hobbies. MDS engines have a great price. But how do they run, are they reliable? Now I might get a MDS .48 or the .58, out of those sizes what size do you think will be best for my 40 inch air boat, it weighs at least 7.7 pounds. Right now I have a K&B .40, but that is to slow for my air boat. Would a three blade prop be good or should I stick with a two blade?

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Old 11-29-2003, 12:49 PM
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rsieminski
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Default RE: Four stroke engine for air boat

No, No, No. I have seen the 18, and 38 run, and they run great. I have the .48, .68, 1.48, and 2.18. All run great except the .48, the .68 being the best running overall. The .48 will run with an idle bar plug, but I've not had any reliability with it at all. The .68 would be the choice engine in the lineup, almost as powerful as a .91.
Old 11-29-2003, 12:52 PM
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Default RE: Four stroke engine for air boat

ORIGINAL: yamblaster2cool

Hi, I just checked out Horizon hobbies. MDS engines have a great price. But how do they run, are they reliable? Now I might get a MDS .48 or the .58, out of those sizes what size do you think will be best for my 40 inch air boat, it weighs at least 7.7 pounds. Right now I have a K&B .40, but that is to slow for my air boat. Would a three blade prop be good or should I stick with a two blade?

<<THANKS>>
With the 18 , I had/have no problems with it at all. It runs very strong and reliable. With an electric starter, it pops off an the first try. Runs are consistant using 15% fuel.

With the 40 though, I did have some problems from the start. HOWEVER, it was not the engine itself. It took me a while to figure it out. The 40 is mounted on my Air Force, with the stock tank setup, I could not get the engine to run more than two minutes. I found the problem to be in the tank setup itself, not the engine. I have since replaced the stock tank setup , put in a dubro 6oz tank, new fuel lines with a two line setup and the fuel draw problems are no more. Sometimes it takes us older farts a little longer to solve problems, but we figure it out in time.

The 40 moves my Air Force with authority, but then it is a pretty light hull. A lot would depend on the weight of yours. Physically, the engines are almost identical, internally is where the difference is. If your hull is between 3-4# I'd go with the 48. Over that, I myself would opt for the 58. That would be how I would go. Others may feel different.
Old 11-29-2003, 12:55 PM
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Default RE: Four stroke engine for air boat

ORIGINAL: rsieminski

No, No, No. I have seen the 18, and 38 run, and they run great. I have the .48, .68, 1.48, and 2.18. All run great except the .48, the .68 being the best running overall. The .48 will run with an idle bar plug, but I've not had any reliability with it at all. The .68 would be the choice engine in the lineup, almost as powerful as a .91.
Here is more experience speaking for ya'.

Sounds like good advice to me.
Old 11-29-2003, 01:01 PM
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pro27
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Default RE: Four stroke engine for air boat

As far as 2 blade vs 3 blade props....

Dunno....... have always used 2 bladers as I saw no need to try 3.
This may be an idea for a new thread....................
Old 11-29-2003, 02:33 PM
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yamraptor2cool
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Default RE: Four stroke engine for air boat

I heard mixed reviews about the MSD engines. People said they take a long time to break in, is this true? What do you think of the O.S. 46 LA? My .40 K&B runs great but does not have enough power for my air boat.
Old 11-29-2003, 03:03 PM
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pro27
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Default RE: Four stroke engine for air boat

I put about 16 oz of fuel through my MDS 18 before I started leaning it out. Now it runs like a charm.
The 40 did seem to take a bit longer. but with everything being bigger, (piston/sleeve) i expect it to take longer.
I tend to give my engines plenty of "rich" running time for breaking in. I generally don't start leaning it out until I have at least 16 oz of fuel through it.
It's just how 'I' tend to do my breaking in. Lots of people have their way they prefere.
Old 11-29-2003, 07:29 PM
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yamraptor2cool
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Default RE: Four stroke engine for air boat

Do they still make the mag .52? If so were can I get it at? It's not at Tower Hobbies.

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Old 11-29-2003, 09:30 PM
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rsieminski
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Default RE: Four stroke engine for air boat

Hobby People for $99:
http://www.hobbypeople.net/gallery/210760.asp

Just Engines has the ASP .52 for a couple of bucks cheaper:
http://www.justengines.unseen.org/ASP.htm



DATA:
PROP PERFORMANCE
11x6 Radio Active [RAM] 2.400 13,400
11x7 RAM 2,400 12,800
11.5x5 Bolly Clubmans 2,400 14,400
12.25x3.75 APC 2,200 13,200
12x6 RAM 2,200 12,000
12x8 APC 2,200 10,000
13x6 RAM 2,200 10,400
13x4 APC 12,600
Old 11-30-2003, 02:01 AM
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pro27
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Default RE: Four stroke engine for air boat

Where in the States can you even get an ASP ???????????
Shipping from overseas (Just Engines) I'm sure would not be cheap.

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