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Old 02 May 2010, 12:53   #1
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Country: USA
Boat name: The Boot
Make: Avon SR5.4
Length: 5m +
Engine: Suzuki DF70
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Posts: 270
main outboard transom setback bracket for Avon Searider 5.4 meter / 18 foot rib

Hi,

I was wondering if putting a 28" or 12" setback outboard transom mount would help the ride and efficiency of my searider rib? It has a 70 hp Suzuki 4 stroke on it. I'm running with an 18 pitch propellor but was hoping to go back to a 19 pitch if I can improve the efficiency by reducing the drag. I also want to improve the ride.

My boat has been modified from the center console motorcycle style seat to a standup pilothouse. The dry weight of the boat has gone up by probably 200 lbs due to the pilothouse that I custom built. The weight is also a bit more forward on the boat so the transom mounted outboard might give better stern weight for improved planing / efficiency.

I looked at the willardmarine.com website and they have a 28" setback for their 5.4 rib. Although their 5.4 is a bit beefier than the Avon 5.4. Theirs is probably more closer to the Avon sr 6 meter.

Would anybody have any thoughts on this modification? Thanks.
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Old 02 May 2010, 15:01   #2
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Reading up a bit more it seems people are saying that a jack plate will not help fuel economy in a cruising boat. It is also becoming apparent that a 28" setback would be way too much. Maybe 12" if anything at all.

I do know that I could use a bit more stern weight to improve the balance of the boat so maybe the 12" setback would help in that dept. Maybe I would be able to lift the motor a tad to reduce drag and thus allow me to go from an 18 pitch back to my 19 pitch prop.

Any ideas would be appreciated.
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Old 03 May 2010, 03:13   #3
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Sorry, no help here. My boat came with the motor pushed back about 2', so I can't offer any kind of comparative experience. I specified the pod to try and recover deck space for dive gear (and it worked.)

If you're considering something like an Armstrong bracket (basically a box that gets attached to the transom and has a small transom to mount the motor on), you should be aware that a lot of the offshore fishing guys add these to compensate for overly heavy engines, as they add quite a bit of buoyancy at the back. You do get a bit more arm for the motor's weight to act on, but I think (and this is from listening to others) that's offset by the added buoyancy.

Luck;

jky
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Old 03 May 2010, 17:29   #4
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I found a jackplate with 12" of setback. If this will give me about 200 more rpms at WOT thats all I need to be within specifications on my outboard to run the 13 x 19 pitch stainless propellor that I have. Right now at full throttle my engine rpm tops out at around 5100 rpms if I put on the 19 pitch prop which is out of the allowed rpm range of 5200-5600. So to be safe I'm currently running the 18 pitch.

With regards to the arm/swing weight added by the setback I will probably just store more gear in the forward part of the boat to correct any excess stern weight.
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Old 03 May 2010, 17:59   #5
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I'd be interested to hear your results. Not heard of anyone using a jackplate on a Searider before.
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