prop mods

[ddaigle]

Been working on my "experimental " boat. Took an old prop, a hammer and curved piece of wood and put a serious cup on the prop. Was able to raise the motor a good six inches without ventilating. The object of this boat is to see how shallow I can get it to run. Went in about 4 inches yesterday without a tunnel. Anybody else have experience with modifying props or any advice on cup design or diameter reduction?.

 

[bayman]

Re: prop mods

Sounds cool ddaigle. 4 inches is pretty shallow!<br /><br />Sounds like you might go through a lot of props this way too.<br /><br />Some prop shops have very advanced software for working with props. <br /><br />I'd take a look at motors like Mud Buddy and Go Devil since those are known to run in really shallow water.<br /><br />Good luck!

 

[ddaigle]

Re: prop mods

My objective is to run shallow without tearing up the bottom as mud buddys and go devils do. And to do it without a tunnel hull and the problems these can cause.(loss of floatation, Etc.) My friends here in the Laguna Madre can run very shallow in their tunnel boats but if they stop in the shallows they are very stuck. I am trying to bypass these problems, but it can be very expensive to have custom props made so I am using the hammer and wood method.

 

[LubeDude]

Re: prop mods

I have done this in the past with decent results, I think the problem comes into play with balance.<br /><br />I am an old body man, and had dollys and metal hammers and worked them very slowly. I was able to add or remove cup with good results by working slowly then grinding slightly and polishing. I even removed material to gain RPM by making templates of one blade after I modified it to match the others. Not sure its for everyone to try though. An out of balance prop can destroy your outdrive.

 

[Dhadley]

Re: prop mods

A trailer ball works good too. <br /><br />Especially if youre at a race and bump something coming in after a successful test. It might not look pretty but it worked. Its amazing what we'd do for a $5.00 trophy.

 

[ddaigle]

Re: prop mods

Thanks for the input, havent had any vibration so I think I'm ok on balance. Really like the trailer ball method. Would reducing diameter help? With all the cup I have installed its really biting well and I have lost some rpm, also I am really on the edge with water pressure at this motor height. I have 12 in. setback and prop shaft is even with bottom of boat. When I trim it up it really flies over the shallow stuff but I lose water pressure and have to trim down. Would some kind of scoop work?

 

[shep70057]

Re: prop mods

I have a 15 pitch 4 blade power tech flats super cup prop that I jacked up as high as possible on my boat without it ever ventilating. PT stated that this prop was made to run through a golf course in the morning dew.

 

[Dhadley]

Re: prop mods

ddaigle, yes scoops work. And work well. OMC used to make some but they have been NLA'd. <br /><br />Trick #2 -- If you remove the lower unit and look in under the pump in the chamber where the water comes in you'll see the bottom holes are not at the floor of the chamber. Basically there's enough room for another hole below the bottom one now. You can add another hole or extend the existing hole down to that floor. Then plug the top 2 on each side. Without raising the motor you've lowered the water pick ups. The downside is that the screen doesnt go to the bottom either. <br /><br />Trick #3 -- a nosecone with a low water pick up. The Grassmaster (or Flatsmaster) style from Bob's Machine works well. The water pick up is on top the nosecone not the bottom. Either will work but the pickups on the bottom tend to pick up more mud and stuff more. The downside -- a nosecone may slow you down at these speeds.<br /><br />Trick #4 -- A boat mounted water pick up. A pickup is mounted on the transom and hosed over to the water pump. Same downside -- pick up mud and stuff.<br /><br />Trick #5 -- pump water to the motor from a livewell. Any debri should fall to the bottom of the well and the cooling water is pumped from the middle (or so) of the well. Downside -- dont run out of livewell water.<br /><br />As long as the prop has bite, you can go higher with the X dimension. Water pressure is the limiting factor. We've seen custom props that stayed hooked up after a low water pickup was out of the water.<br /><br />Generally speaking most guys send their unit to Bob's Machine and have the nosecone low water pick up installed.

 

[ddaigle]

Re: prop mods

Thanks guys, Shep I have been looking at the power tech props but didnt want to shell out 400$ for a prop that might not work. Thanks for the info. Dhadley, Will a regular live well pump put out enough water for the motor? I had thought of something along these lines but wasnt sure if it would work, I figured you would know. Also, would it be feasable to run an outboard with a radiator or is the cooling system too small? I have heard it is possible to dry out the exhaust and I was thinking about a radiator from a v-8 car with an electric fan or two. I really Enjoy experimenting with this. Thanks

 

[Dhadley]

Re: prop mods

The radiator wont work. Or at least it never has on the ones I saw. Drying out the exhaust is for power (there's other things that go with that) at real high rpm. And over time it can burn the paint on the midsection. <br /><br />The livewell supply is a short term deal for running shallow and then reverting back to normal pick ups. The pump from the well has to be big enough to pump enough volume to maintain pressure. It should be hosed in as an "also" type supplier once you jack the motor that high. Once past the shallow, the motor is lowered and that pump turned off.

 

[walleyehed]

Re: prop mods

The guys here running up the Red river are using 1100-1200GPH pumps for this, and I guess it works quite well when traveling over sand bars and such. Most of these are 150HP-up on huge, flat-bottom boats.