Help with prop and set up on new ride

[mohill]

Just got new boat 2013 1546 Alumacraft aw dd, boat weighs 320#. Running a johnson 40 tiller on a 6 inch set back spinning a stock 17p omc sst prop. I have the anti vent plate 2 inches above the bottom of the hull. Ran the boat, rpms are at 5800. Had a lot of porpoising and tried to trim through it, no luck. Moved gas tank around, no luck. When trying to trim through the porpoising I could feel the boat trying to lift and sit back on the rear foot or so of hull but wouldn't quite get there and kept bouncing, really more like skipping at this point. After reading threads I feel that I am in need of a more performance driven prop to carry the bow and help with the porpoising. From what I gathered a cleaver style prop would be good (SRG fellas) for my application. Also, more top end speed would be good. Same motor and prop on another boat of mine spun 6200 rpms when the hull got some lift.

Any suggestions on set up, prop selection, pitch needed if going to diff style prop, etc. is much appreciated. I do not want to beat a hook into the hull.

Pictures to come tomorrow when I get some day light.

Thanks in advanced

[omcstratos]

You are gonna have to flip the boat over and give the hull some TLC. Thats the only way to fix it. That model boat bottom isn't perfectly true

[mohill]

What kind of tlc you talking? Knocking a hook into it? Just looked at the bottom and its flat with a very very slight rocker towards the stern it appears. Pics coming shortly.

My thoughts are knock rocker out and any other imperfections to get hull as true flat as possible. Then test run before further hull mod. My straight edge became an eye opener for me.

[omcstratos]

You got it. A few guys around here run those and have the same problems. You are always gonna have to spend some time setting up a production boat to get it better

[mohill]

Omc I see you are a sc fella. Me too down here in charleston.

[capnzee]

Omc I see you are a sc fella. Me too down here in
charleston.

That last foot or so of rocker will do it every time. I have seen as little as 1/32" of an inch rocker cause a porpoise such as you describe. Not only uncomfortable but can be unsafe. Turn the boat over, straighten the bottom over the last 4 feet, sharpen the trailing edge at the transom. If this doesn't work, then you may have to work on balance. If you still can't control the bounce you may have to install a small pair of trim plates off the transom. This will not help your speed but should stop the bounce. See if your friend will let you try his prop, if it works buy one just like it, but you still got to flatten out the bottom.

[mohill]

Is the best way to true up a hull to hit it with a mallet and chunk of 2x4 ? Or is there a better method y'all have found. Really trying not to mess up a brand new boat but need to get the rocker out.

[champ20B]

Is the best way to true up a hull to hit it with a mallet and chunk of 2x4 ? Or is there a better method y'all have found. Really trying not to mess up a brand new boat but need to get the rocker out.

Sounds like a nice fishing boat. Unfortunately, being aluminum, and having experience thereof, You can't get it perfect at all. An aluminum boat is the wrong boat to aim for dynamically peaked performance. It would be possible with the old convex bottom style as it was more resistant to warping under pressure, and that would be without rivets! LOL!!! I would suggest to just forget it. 5800 RPM sounds like the optimum power range for your motor, so youv'e got it right on pitch. I would suggest a standard style prop and to run a bit lower kicked inward a bit or just take what your running now and try it kicked in/under to smooth it out. It might be a little less than hoped for, but it will only do what it is meant to do with 40HP regardless. It will still be a formadible speedster, but mostly a great rig to escape society and enjoy the wonders of nature with a RC cola, a good ol' moon pie, and a fishing rod! Heck, I've got to go fishing now just thinking about it!!! And yes, you probably can guess, I'm from the old south.