vw 1600 airboat direct drive 60 X 32 gsc wood prop

[banditairboat]

Hi guys, was wondering if somebody can help me with my airboat . It is 1600cc dual port with solex 34 carb. I am using a 60 32 gsc prop and I don't find it performing the way I expected. My boat is 14 X 5 fibreglass . Everything hull/cage/engine is just under 600lbs. Any suggestions would be great

[busdaddy]

60" is pretty coarse, my knowledge is slanted towards airplanes opposed to boats but something as unaerodynamic as that should have something closer to 48" or even much less to get it moving on that HP, right now it sounds like you are trying to start out in 3rd gear.

Is that a common pitch/length for that sort of boat and powerplant?
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[banditairboat]

Culver props recommend a 62" X 32 pitch for my application. I am waiting for this prop to arrive. I put new cylinders/pistons and new heads before I built this airboat. Everything is stock. I don't know if I am getting the correct reading from the rpm gauge. it is one I used from a 2 stroke snowmobile. It reads 1000 rpm at full throttle but to me I think it is turning much faster than 1000. Not sure if this gauge works on these engines correctly

[[email protected]]

The rpm indicator should be hooked up to the coil and it is set to how many cylinders exist. So if you have a two stroke tack and set it to 2 cylinders it would read the correct RPM. Since VW needs 4 spark firings for two rotations you want to set you two stroke rpm indicator to count to 2 for each single rotation.

If your tachometer is hooked up to a single spark wire, the RPMs would read exactly half the actual RPM.

Beetle engines are supposed to idle at 850 rpm. I tell you that so you can hear when the beetle is idling about the right speed and look what multiple the tach is off, or utube a beetle idle, compare that to your VW engine idle and now see how far the tach is off.

[banditairboat]

Thanks, that means my engine is turning 2000 rpm with the 60" 32 pitch prop. Maybe it is still not enough rpm. But I used the boat on ice/snow and it cruises fairly good. Haven't had a chance to try it on the water yet. its my first ever experience with airboats and vw engines. maybe a new carb would help too because the 1 I am using isn't rebuilt

[banditairboat]

Does anybody know if I should get more rpm with this prop and what should I do to get it.

[Letterman7]

Sounds to me that you need to find an airboat forum or even join in an experimental/ultralight aircraft forum that are familiar with the VW engine and prop combinations. I'd imagine most of us here aren't that familiar with the pairing.. though you could get lucky! From what I have peripherally read there should be a gear reduction box to bring the rpm's up or down to suit the craft... hence my suggestion for an aircraft or airboat forum.

[coad]

A Google search shows over 300 posts about airboats on The Samba. Maybe read through those and contact the people in those threads who sound like they know what they're taking about?

There's also quite a few photos in the gallery. Again, maybe ask some of the owners who have posted photos.

[mgreaves]

[mgreaves]