hello. first time poster. great forum.
i am building a homemade surface drive mud motor for my 10' jonboat. this will be a project for me and my 10y/o son this winter(trying to find other things for him to do before he discovers the bad things we(I) found as kids). we already have most of the important issues figured out(bearings/pulleys) but were wondering how deep the gear box should be. we figure it should not extend past the transom, but should the driveshaft be level with the water at idle? also, how long should the driveshaft be? i am a machinist by trade and also own a mig welder. we were thinking of using a 7x5 prop. any help would be greatly apreciated. i drew a picture in paint to explain what we are looking for and also attached a photo we found searching online for ideas. our mud motor will be simular.

Check this post out lot's of pic's it might help.

viewtopic.php?f=41&t=5787

your probably going to want some form of trim so keep that in mind

Plz read and comment

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In my opinion, depending on what size 10ft jon you have you may be at the max limit in weight with a 7hp surface drive on the back for any gd performance. In other words your transom if you get over about 50lbs motor weight will sit too deep in the water and not be ideal. You may want to step up to a 12ft if possible. Probably should build a 3 to 4hp motor like dixie mud motor at 46lbs for a 10 ft jon. Just my opinion from experience, but I say if you think it will work go for it and see what happens, we don't know until we try.

Sorry I got long winded and did not answer your ? To answer your ? there are many variables involved in deciding drive box length. On my 6.5hp homebuilt short shaft mud motor my box sits about 3 to 4 inches above the very bottom of the boat but unlike the standard 27 to 32 inch shafts mine is longer at 40 inches. This allows for more adjustment for my trim and the angle of the shaft to the water. Just how my design worked out and not sure how much it affects performance either way but I am getting gd service from mine and speed.

how did you get that pulley on that electric clutch, that is sweet

a lil sneak peak from our maiden voyage

http://www.youtube.com/watch?v=Yiht0MUu ... vGW1cbLiw=

http://www.youtube.com/watch?v=nFY5nNMy ... jAQtFSOoA=