Repower Bertram 46.6

Repower with Cummins QSM 11

This is from a posting on another web site. boatdiesel.com I have a simlar situtation. 1976 Bertram with 8V71TI looking for posibile repower options. I like the boat but would like to get better perforance.

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Maybe this will help.................We finished a heavy 46 Bertram about 6 months ago that had 8-71 TI's in it with performance numbers just about exactly like yours...We went with QSM 670's w/ ZF 350A 1.75 gears and ZF 28 x 30 4B props, AQ 22 2" shafts and she cruises easy in the mid-20's at 1900-2000 RPM............Good combo..................Props move boats and not engines and, with a heavy boat like yours or these older Bertrams, stay with the maximum practical prop diameter you can go with, with a .7 or higher DAR.......Look at local support to help guide you with what color to choose.. The Yanmar 6LYA3 is not a choice IMO.. With the C-9, you need 2:1 gears, with the QSC 600 you'll need 2.5:1 gears, with a QSM-11, 1.75:1 gears would be right..................I do not believe your budget at 80K is really doable unless you do most all the work yourself, your boat is already in pristine condition, cut lots of corners, have friends in the boat yard business and/or shop for something less than new current equipment.. Don't forget, going from 30 yr old 8-71 Detroits to a modern 100% electronic engine is more than just a typical repower....BTW, in your calcs, you need to account for a 3000-5000 lb wt reduction as that's what you will have going from your Dertroits to a modern engine.................................................................................Tony
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