I am part way thru building a longtail powered by a stock 420cc lifan electric start. Has anyone used this engine? I am putting it on my 14' v bow. Its about time to order a prop and I would be thankful for any input on size and brand advice. It will be a oil lubed all bearing drive with a u joint at about 10 degrees. I was thinking a 8x4 but the cart forums are saying these motors have a lot of low end power so I am not sure if that is big enough. My last home built lt was a 6.5 hp that pushed my boat at 11mph with a hill 6.5x4 prop. Thanks for helping a first time poster.

My first build was with an engine similar to that lifan, I used a 16hp durostar when they still had them available. Anyways I used a RH 8x4 for that build, and really like it (3450 rpms). If you are worried about too much you could also go with Hopkins they make a 7.75x4. We've also gone the BW route and had great service with them. Good Luck!

Thanks swampdonky. I will put up some speed info once its all done. Hopfuly before early teal season here in north florida.

The 8x4 was the right choice. Getting 15 mph so far.

i have the lifan 420cc. that big block has got some torque. easy to upgrade. most all parts are interchangable with the gx390. agk or nrracing are good sites for parts for them. put the larger bored carb, high flow intake and exhaust. advanced timing 4 degrees. its prolly about 17-18 hp now.

How did you advance the timing? Did you have to upgrade the valve springs. Thanks for the info.

you can buy advancd keys for them. i just filed my key down to four degrees advanced. you have to remove the pull start, cooling fan and flywheel to get to the key. wont upgrade springs until i get a better cam. doing so with stock cam can sometimes wear the lobes down on yur cam. depended on how stiff the springs are you put in. worked racing cams are welded hardend steel lobes.