I have aquired a 2001 SBDB that needs a motor board Have researched the forum and found Steve Sanfords Motor Board Details https://duckboats.net/community/threads/motor-board-details.334141/ I do not see the overall length of the motorboard. I have a 15" mercury 15 hp will start with a 2"x10" trated SYP starting at 18" long with the 2 standoffs 1.5"x1,5" 10" long with the rounded edges and bottom for the handhold. Will mock it up and adjust the height of the motor by cutting the top of the board to get the cavitation plate even with the transom bottom unless someone can suggest an overeall height.
South Bay New Motor Mount
- Thread starter John Ki
- Start date
Steve Sanford
Well-known member
Good morning, John~
The reason I do not note total length on my motor boards is....it varies. I regret that I never consulted Red Magnus (South Bay originator) when I still could. It seems the optimal measurement - which is the height above the stern deck - varies from motor to motor (always assuming 15-inch shaft). Theoretically, of course, the (anti-)cavitation plate should be level with the bottom of the hull. But, it seems performance does vary engine to engine.
Later today - after it's light and I'm back from my dentist - I will measure a couple of the South Bays I have here in the yard - for the above-deck height.
Stay tuned,
SJS
Steve Sanford
Well-known member
John~
I just - finally - got out to measure the heights-above-afterdeck on the 3 South Bays here. The dimensions (on centerline of afterdeck to top of motor board) are: 4-1/4" 4-3/8" 5'-0"
I believe different owners played around with mount heights for different engines - both brand and HP - to find optimal performance. I imagine they were concerned about: 1) getting up onto a plane; 2) reducing porpoising; 3) top speed (which younger gunners evidently refer to as WOT (which I gather = wide open throttle).
I'm a sailor at heart and am happy if my gunning vessel cruises steadily at around 12 or 15 kts. (note Old School abbreviation.....)
With this info, you may want to mock up a "trial mount" (old School term: jury rig) - with 4-1/4" above the deck - then add spacers 'til you find your sweet spot. You could make it out of untreated lumber - and temporarily - but securely - mount with a mild caulk. Then cut your "real" mount to its final height - seal with 2 coats epoxy - bed in 3M 5200.
Hope this helps!
SJS