countryrook,
The 'Vac-U-Tug' should work okay, and so would the 'pusher' that Phil makes. Actually, the 'pusher' would probably do a little better because of the type of boat it is. The power up-grades that Phil has available (big batteries too) would be a good option if you gas boat is very large.
Retrieval boating is not the simplest thing in the world, so take a look at the different ways of doing it. If you're going to push a boat you'll need to know 'how'. Same for dragging one, learning 'how' to snag the thing. Practice is a very good thing to do!
Pushing with a boat that has a 'pointy' hull isn't easy, keeps slipping off the pushed boat.
Having 'extra' power is nice when you need it. So is good directional control.
Pulling a boat requires that you snag it some way. Several 'ways', all have advantages/disadvantages. Pick whichever you feel comfortable with.
Where you attach the tow rope can make a big difference (fore or aft of the prop) in the towing boat's manuverability.
How far you have to retrieve, and how big the 'dead' boat is will also make a difference. Short distances means ~almost~ anything can work. Long distances means bigger batteries (same for the size of the retrieved boat).
The shape of the bow of a retrieval boat and it's power, can turn your 'dead' boat into a submarine. Gotta be careful, you know?
Practice!
More practice!
- 'Doc

PS - This is NOT a definitive expalanation of retrieval by any means! Just some thought about I've done it wrong...