Belt Redrive/Reduction help for Yamaha RX1 engine

Airboats with smaller powerplants.
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AlaskanOutdoorsman
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Joined: Sat Apr 20, 2013 3:34 am
Location: Alaska
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Belt Redrive/Reduction help for Yamaha RX1 engine

Postby AlaskanOutdoorsman » Fri Mar 17, 2017 2:21 am

Hi all.

I'm looking for some help build a reduction drive for my airboat. To be frank, I jumped into a rebuild project that I don't have all the knowledge for so I'm posting for any and all assistance I can get. In short, I live in Alaska and sold the 65HP Rotax engine, 3:1 C-type gearbox and IVO prop on my 12' airboat after the engine blew up and the prop took some damage. I've since rebuilt most all of the boat.

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After much consideration on engine options I decided to install a Yamaha Genesis 4-cycle snowmobile engine from a 2004 RX1. The engine is about 160 lbs installed and produces 120-150 HP depending on engine RPM. These engines are used quite a bit in the aviation world without any problems with an adapter and gearbox assembly and I've found tons of information on that application. I plan to add a turbo kit to get an estimated 200HP on pump gas in the future but I'm not there yet.

Stock engines used in aviation generally require an adaptor/gearbox combination which is rather expensive and may not hold up to the extra turbo HP. I just sold a gearbox I had considered using. This leads me down the redrive/reduction drive road unless I find something affordable online.. but I have ZERO knowledge on how to build one and to date I have not found anyone in Alaska that can offer any advice other than "go to the forums" or "sell the mini" so here I am...

Would someone be kind enough to point me in the right direction? Where the heck do I start?

Any and all assistance is very appreciated.

User avatar
AlaskanOutdoorsman
Southern Airboat Member
Posts: 5
Joined: Sat Apr 20, 2013 3:34 am
Location: Alaska
Contact:

Re: Belt Redrive/Reduction help for Yamaha RX1 engine

Postby AlaskanOutdoorsman » Fri Mar 17, 2017 4:31 am

I forgot to add I was cautioned to steer clear of cog belt PSRUs for YG4 engines due to their high speed, torque and HP and was told there may not be cogged belts rated for max engine RPM of 9000. These engines red line around 12000 rpm.

An immediate option would be spending $2000 on a SPG4 gearbox and adapter but the box is only rated for 180hp. The box would work with a stock engine but wouldn't handle the extra 100 HP with the turbo. I'd rather not spend that kind of money right now anyway, this project has killed a couple extra piggy banks than I had expected.


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