24 Hp Mudmotor Finally Finished

your cav plate should be parallel with the water surface ...so no need for bends an things ...suspect you have it angled up too much at the front

 

Keeping the prop submerged with a cavitation plate will have to cause drag.

How about controlling the depth of immersion with a push pull cable as found on the steering of many outboards?

FF

 

thats a daft idea most of these longtails have a plate above the prop parallel with he water surface to stabilsie the positon of the prop under the water

 

"ABOVE the prop parallel with he water "


Perhaps it is working as an end plate to stop airation , as well as a depth of immersion device?

 

when the cavation plate is parallell with the water there isnt enough force of water riding over it to keep the prop in the water. that is why i am thinking of adding the wing to the back of the cav plate. i have included a crude sketch of what i a going to try. the cav plate is to keep the prop from cavatating and the wing will be to help keep downward force on the prop from water running over it

 

Put some cup in the prop. Happened to me with my boat. Learned on the forum here that I wasn't cavatitating, I was sucking air. More cup in the prop and I went from about 20 mph to 35 mph. Thats 65 HP though. You should see around 18 to 20 with that engine. Go devils engines are direct drive. A 23 HP has a spec at 18 mph. Check out Go devils props. Alot of cup.

 

I think we have discovered that these longtails work better when geared down about 3 to 1 the genuine Thai item is even lower geared . What we have on an outboard is a max prop rpm of about 3000 but thats with the motor sized to get the boat up on the plane at about 20 % slip. What you have with your 24 hp is the prop going too fast and pushing a heavy boat so the slip is probably 50 % hence you only go slow. Reducing your slip with cupping may help but even the weed wacker brigade have discovered gearing down helps a lot as have the 6.5 lifan Honda users.

 

i think your all probably right to some extent. i am going to keep the motor as is for right now so i can still use it this year to go out on the water but when fall gets here i am thinking of doing some kinda gear reduction to the motor. thanks for all the in put

 

I don't know..... Manufactureres make em 1:1. But I haven't read too much about the reduction on the forum here. Reduction seems complicated and unnecessary. Especially when prop can fix the problem.

 

well if its geared down its probably easier to match a prop .....less of an egg beater ......I notice that the genuine longtail props for the 24 hp have about 80 % blade area ( is 80% of a full circle)...I carnt see what prop you have but getting it at the right depth with the right prop and shaft length should cure it

 

I know that this thread is a couple years old now, but I really would like you know how you resolved your issues. I have a couple things to add. These go-devil designs are well thought out and when done right should make you a very nice mud motor. After all, that's what they are meant to be. The 72" tail is meant for a certain height transom to ensure the proper prop angle. You mentioned extending you tail which, in my opinion, will just increase weight on your transom and a longer tail will make the motor harder to handle. Around here a common way we fix this is by stepping down the transom to the desired height. As far as the cav. plate is concerned, you will have to tack-weld it at the end and just do some testing. Leave it to where you can adjust it by hand while you are on the water. When you get it right, weld of up. Last think I would like to add is that the prop makes a huge difference. Go with the recommended prop from the go-devil web site. Pitch plays a huge roll. Mud motor props catch a precise cupped angle when they turn. They are made to push through mud and anything else in the water. It will cost you, but a mud motor prop would be the way to go.