Cavitation and Speed and Picture

[Tail_Gunner]

Re: Cavitation and Speed and Picture

Take it down to prop forums, both Walleyehed and Dahadly should be quite capable of getting good resolution if you already have not recieved it here..

 

[ondarvr]

Re: Cavitation and Speed and Picture

I'm with Mikdee on raising the bottom of the extentions. On large ones like these they are normally set higher than the hull for a couple of reasons.

One, is that when they are even with the hull, on plane the boat will be flatter on the water, that means more wetted surface and more drag.

With the bow riding lower it will be pushing more water, slowing it down.


When the stern rides lower, it will tend to push water (and air) to the side when it's on plane. Now the air is just going straight back, not to the sides and away from the prop.

 

[MikDee]

Re: Cavitation and Speed and Picture

Thanks ondarvr, at least you understand my concept, it has nothing to do with the prop right now, as it appeared to be suited to the boat fine before the extensions.

 

[Islandlure]

Re: Cavitation and Speed and Picture

Ok, got it! I have dropped the motor 1 1/2" total from where it was. Placed the tilt pin in the second hole from the bottom and the water right now is smooth as glass and I had the max speed on the GPS at 36.4 MPH. And I can tell you now I will never use all of that. It was making my eyes water and cheeks flap in the wind in that little thing. But I am happy with it, when I load another guy and all of our gear I expect somewhere around 28 to 30.
I totally agree with you guys and understand what you are trying to tell me I just wanted to try to leave the pods alone because I tig welded them to the boat and moving them would be some work. But I know what you are saying and I installed them 1 1/2" up from the bottom because of the exact reason you are describing, but it appears it wasn't enough or they are a bit too long. I am happy with how I have it set now. I don't know if it would go faster but I don't want it too, that was too much already I do thank you all for your insight on the matter. It was much appreciated!

 

[studlymandingo]

Re: Cavitation and Speed and Picture

Since you're obviously handy with the TIG, why not make a way to mount the motor at the back of the sponsons? That would get the motor back in "cleaner" water, and allow you to move it upward considerably. Might be an interesting experiment.​

 

[ondarvr]

Re: Cavitation and Speed and Picture

Sounds like you've got it dialed in now, good job.

 

[Tail_Gunner]

Re: Cavitation and Speed and Picture

Since you're obviously handy with the TIG, why not make a way to mount the motor at the back of the sponsons? That would get the motor back in "cleaner" water, and allow you to move it upward considerably. Might be an interesting experiment.​

Yupper's both WH and Dhadley are constantly advising people on such thing's, id bet they'd get a kick out of it since this has to be a first nice job there by the way good looking boat..

 

[burroak]

Re: Cavitation and Speed and Picture

I thought your object was for more freeboard in the rear. The motor depth should not affect your freeboard.

As I understood it, the reason for the flotation pods were to allow the boat to float in skinny water, a reasonable enough idea; but dropping the motor lower into the water just seems to counter that attempt unless the motor is tilted and push poling begins.

 

[Islandlure]

Re: Cavitation and Speed and Picture

Been running the boat all day, seems to be good. I think I need to look at replacing the impeller or water pump or both sometimes it flow looks weak coming out.
Hey studleymandingo, not a bad idea but I could see that end up pushing the back of the boat down into the water again. But who knows right now I just want to get some fishin done and then this fall and winter maybe tear it back down again and do something else... I can see a tuna tower in it's future jk. Maybe I might just buy a real flats boat, but this thing is pretty fun now and I don't have to worry too much about it.
Thanks to all who have helped, and I hope I can help some of you all in the future, but I am not all that experienced with restorations but if you ever have any questions about boat graphics, decals and such send them my way, because this is what I do! Thanks again.

 

[Bob_VT]

Re: Cavitation and Speed and Picture

Smaller aluminum boats need a deeper bite hith the outboard and I am not surprised by the results.

I agree with mounting the motor as a test off the back of your additions. I doubt it will mage the back ride much lower now since you have increased the overall length. I think it would be the same.

I know your modification has accomplished what you had set out for and any adjustments now or re-positioning of the motor will probably not have that great of effect. You seem to be dialed in.