inboard prop pockets

[jeemboNC]

Gentlemen - I have searched but found no information on the advantage/disadvantages of prop pockets. I appreciate the debris impact protection they afford, but I understand that they compromise handling at low displacement speeds/docking. I assume they make getting up on plane slower/more pronounced stern squat. Also, on single applications (e.g. Shamrocks), I have heard they are less efficient. True? My specific interest is on 24,000# class twin gas powered ACMYs. Thanks. JeemboNC

[jeemboNC]

Whoops - I have to answer my own post. I found the pocket thread that I didn't see before. Read all of it - I think much applies to high speed boats. The pockets of interest to me (SeaRay ACMY) are 'half circles'. As one not entirely expert at docking, this is a concern for me. Any SeaRay owners out there? JeemboNC

[KFB]

Pockets are usually incorporated into a hull to decrease prop draft and deal with issues relating to the driveline or engine placement. Pockets can cause anomalies that include performance, vibration/noise, and other characteristics that are undesired, but properly done, the draft benefits usually outweigh these. Centerline pockets for single screw boats are the most difficult to get right, but also stand to gain the most as far as reducing prop draft. Dockside boat handling is effected in a more pronounced way with the centerline pockets as well. There are many dynamic issues to consider during the development of a hull form that makes use of pockets or tunnels, and there are good and bad examples out there, I doubt that the average owner of a small boat would note any inefficiencies related to having tunnels; all other things being equal and assuming the tunnel design wasn't a complete mess. Hope this helps.

[jeemboNC]

thanks. From what I can tell SeaRay has a reasonably competent engineering group!! But, one never knows. I guess I just need to try it out and see if it tracks straight without yaw and can dock ok. JeemboNC

[gonzo]

The loss of efficiency is considerable. The hull loses a large amount of lift. This is partially countered by the more shallow shaft.