Hey guys im new to MMT and have a question, i just built a surface drive for my 1462 custom tunneled Jon boat, the engine is a brand new 32hp generac set up to run on LP, i abuilt a lower unit for it temporarily, its a 24 inch long shaft with a 10x9 backwater prop, i have not run te engine yet in the water soo im not sure how it will react to a 24t sprocket on the crank and a 12t on the out drive, what do y'all think?

If it doesn't run right you can always use the left over LP for a fish fry.

The engine runs great its brand new, and yes 24 on the crank 12 on the out drive, i build it soo im sure thats what it is.

you trying to spin the prop twice as fast as the engine, that will never work i promise.

It takes a modded 35 to turn a 1:1.2 ratio, I can assure you that your 2:1 is gonna be a turd.

I say try it and let us know how it goes!

I would start with a 1:5.

Maybe a 1:4 since the prop is kind of small.. gears are cheap, props are not..

Really?!? That low of a ratio??? Less than 1:1? If these motors are turning the prop that slow how are they seeing higher speeds than a long shaft?

Ohh wow thats new to my ears! Thank you soo much for that, soo what do you think I sould go with a 1:1.4 ?

I have heard that tunnels are bad, what is the reason for this? Also i plan on putting pods on it to compensate for the draft.

I could enclose the tunnel if need be as well.

Propane has less BTU's than Gas so less energy per unit. If the unit can have the compression increased you can make good power with propane cause it its High octane level.

The more reduction you have the more mechanical advantage you give the motor to spin a given prop.. You need to find a combo of reduction and pitch that will work with the HP you have.

The motor was built by generac to run off propane it has a higher compression ratio than a gasoline generac 990, i didn't just add a propane kit to it, it came like that. Now im trying to figure out what pitch the prop is.

The motor was built by generac to run off propane it has a higher compression ratio than a gasoline generac 990, i didn't just add a propane kit to it, it came like that. Now im trying to figure out what pitch the prop is.

What should i use for a prop? 35+ hp motor.

I build my SDMM with a 1.65:1 gear ratio. Not the best top speed but plenty of power and reasonable speeds. Top off with prop that works best.

HOLY DEAD THREAD, BATMAN!!!