Yamaha 143 HP RX1 engine

[AlaskanOutdoorsman]

Been reading up on the RX1 (carburetor) 143hp 4-stroke engine. With an adaptor ($1500) it will bolt directly onto a Rotax C type gearbox and put out 140hp. The engine is 30lbs more than a 60hp Rotax 582. Looks like this motor has been used on experimental aircraft with good success. Has anyone had any experience with this engine on an airboat? Thanks!

[Corky]

No experience but I've been reading up on the engine and it looks like a great powerplant for an airboat...I see someone made up an adapter plate for the rotax gear reduction to fit that really opens up the possibilities ...

[dr.peck76]

I built an airboat 2 years ago using a newer variant of this engine. Mine was from a snow machine.(2010 yamaha nytro) It is fuel injected has a turbo kit on it as well making between 180 and 200hp. My rig is very overbuilt and weighs in the 1350 lb range but the boat still runs dry. My hull design limits top end to about 35mph, but really that's fast enough. IMO. Check the fourm for my build. This is a great engine platform.

[AlaskanOutdoorsman]

Thanks for responding. Sounds like our hull setup's are similar.. my boat's heavy and I expect the design will limit top end (but I'm looking for a moose hunting rig, not a drag racing machine). Here's a pic, I just finished all the new aluminum work, just need to pull the engine/prop/stand off and decide if the RX1 will work.



After way to many hours sorting through google searches about engine options it looks like using the YG4 motor and Teal Jenkin's adaptor ($1500) that allows the easy use of a Rotax C gearbox (I have a 3:1) is the best bet but I'm not sure if the gearbox will handle the extra HP from the turbo. At 8500 RPM Teal's prop was spinning 2733RPM @115hp and the Rotax gearbox held up with clutches w/o problems. Evidently other aircraft have reported up to 130hp stock under the right prop conditions.

I've been researching the turbo kits, it doesn't seem like much to get 200hp. I read tonight with a little engine work you can get 250hp with regular gas; this is closer to my goal. So far I haven't found any turbo HP charts. Still looking.

I'll look for your link, expect a PM in your box once I've read through everything - I'm sure I'll have questions.

[Coyotes-R-Us]

Boy to I feel under gunned with My little 1600cc Bug motor !!!!!

[dr.peck76]

I've seen extreme cases where snowmobilers take these engines to north of 400hp. Absolutely nuts.