Classic AquaSport

Aquasport Mechanicals - things that need a wrench, screwdriver or multimeter => Engines & engine woes => Topic started by: Argo on January 14, 2007, 04:32:40 PM

Title: question about twins
Post by: Argo on January 14, 2007, 04:32:40 PM: What would be the drawback of putting on 25" twins when the transom calls for 20"? I got a bracket for my boat from D&D and it has measurements for install assuming 25" shafts. should I install it with that measurement or should I go with a 20" shaft measurement? I just saw the brochure on the board with regards to transom heights. remember that my transom is enclosed and I will have the bracket on it.
Title: What boat? hull configuration?
Post by: 22FamilyFish on January 15, 2007, 05:40:21 PM: Refer back to the bracket (manufacturer) for installation support.I always thought the bracket needed to match the transom height??
Installing 25" outboards on a 20" transom height would have negative and undesirable effects on performance.As long as the cavitation plates on the outboards are even with or slightly above the bottom of the boat,your ok.The bracket may alter(or raise) the original (non-bracket) configuration and allow the use of 25" shafts,depending on installation/application.Check with D&D(manufacterer).
Know what your getting for sure in the outboard department BEFORE mounting the bracket.
Title:
Post by: warthog5 on January 15, 2007, 06:39:52 PM: Huh?

My boat was designed for 20in shaft's originally. the transom was enclosed and a D&D bracket installed for 25in shaft's. I hung 2- DF-140's w/25in shaft's on it.

I'm kiching the idea around now of building a new bracket ala Seamark Marine Products. http://www.hermco.net/brackets.html (http://www.hermco.net/brackets.html)

The D&D has room for improvement in the flotation tub.

http://www.classicmako.com/projects/xshark/bw19.htm (http://www.classicmako.com/projects/xshark/bw19.htm)
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Post by: warthog5 on January 15, 2007, 06:46:58 PM: By the way. I will be moving the motor's up to the bottom mounting hole.

I started in the 2nd hole from the top. 2.3mpg @ cruise. [4200 = 25mph]

I moved to the next to bottom hole. 2.8mpg [4200 = 26mph]

It still has room for improvement as to motor height. I belive the bottom hole will put it on the money. I'm also going up 2in in pitch. From 18 pitch to 20 pitch.
Title:
Post by: Argo on January 15, 2007, 07:08:24 PM: I am getting a new bracket from them and I plan to put the 25" motors on it. what is the downfall of having an extra 2" hanging down in the water. their bracket is gonna be 4" lower and I should be able to raise the motors up around 3-4" with the adjustment holes. any thoughts. it is hard to find counter rotation in 20" shafts.

what do you think needs improvement on the D&d?
Title:
Post by: warthog5 on January 22, 2007, 10:12:14 AM: Quote from: "Argo"
I am getting a new bracket from them and I plan to put the 25" motors on it. what is the downfall of having an extra 2" hanging down in the water. their bracket is gonna be 4" lower and I should be able to raise the motors up around 3-4" with the adjustment holes. any thoughts.
Have your read this? http://www.dadmarine.com/doc.htm (http://www.dadmarine.com/doc.htm)

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is hard to find counter rotation in 20" shafts.

YES, not likely to find one

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what do you think needs improvement on the D&d?

the shape of the tub. Look at the Yellow line. [More Flotation]

(http://img.photobucket.com/albums/v196/Warthog5/bracketside.jpg)

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