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Old 26 July 2013, 19:26   #21
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Mercury makes a short shaft 40hp. That is the only motor I was able to find new. I also found a guy that would make a bolt-on transom riser for a longer shaft motor
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Old 29 July 2013, 10:50   #22
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How low below keel does anti-cavition plate should be on F470 at transom? My transom is 18". Common wisdom is 0-1" below on regular boats. That puts motor quite a bit above transom. Should anti-cavitiona plate be lower on F470 because of speed tubes?
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Old 30 July 2013, 12:47   #23
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Quote:
Originally Posted by SIBRider View Post
How low below keel does anti-cavition plate should be on F470 at transom? My transom is 18". Common wisdom is 0-1" below on regular boats. That puts motor quite a bit above transom. Should anti-cavitiona plate be lower on F470 because of speed tubes?
20" shaft.
The wisdom is supposedly that the deeper prop (and deeper exhaust) will be quieter for your commando beach landings...

After trying it, you might consider a small black of wood under the motor mounts to raise the engine an inch or two. You might get a little more speed with less splashing.
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Old 30 July 2013, 12:51   #24
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So is it an inch or two? I'm thinking to bolt motor down. Don't want to drill too many holes.
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Old 23 March 2014, 21:20   #25
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So I ended up replacing the short shaft with a long shaft (or extra long shaft, can't quite tell) Suzuki DT-40. The DT-40 sits about 4.75" below the keel. I've noticed excessive splashing and fuel consumption. Do I need a Transom Riser?
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Old 26 June 2014, 15:39   #26
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Transom Riser Fabrication

I have decided to design and fabricate a transom riser. So what is the optimal location for the cavity plate on a Zodiac F/FC-470? Is it exactly flush with the keel or is it 1/2 - 1" below? If it is exactly flush will I have issues with loosing traction when there's a lot of waves? I have drawn up a design in CAD. I am contemplating making it adjustable but I don't know if it is necessary. On the other hand I don't know what the sweet spot is. Currently I need to move the transom up about 4.75" in order to make the cavity plate flush with the heel. Should I make it flush or set it slightly below?
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Old 26 June 2014, 16:04   #27
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I have decided to design and fabricate a transom riser. So what is the optimal location for the cavity plate on a Zodiac F/FC-470? Is it exactly flush with the keel or is it 1/2 - 1" below? If it is exactly flush will I have issues with loosing traction when there's a lot of waves? I have drawn up a design in CAD. I am contemplating making it adjustable but I don't know if it is necessary. On the other hand I don't know what the sweet spot is. Currently I need to move the transom up about 4.75" in order to make the cavity plate flush with the heel. Should I make it flush or set it slightly below?
Good idea! I've been happy at 1/2" below. Only experiment would tell for sure but I think Raising it 4"+ makes such a massive difference that last 1/2" wouldn't matter nearly as much. Adjustable would be nice at least for experiment. Does your motor have number of mounting holes? It may allow to mount at meaningful height. If you keep your 1/2 sacrificial plate make sure clamps can grip such thick transom. Mine would not. I only have at best 1/4 of threads left after clamping over transom + 1/4 alum plate x2
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Old 26 June 2014, 16:16   #28
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The motor only has one pair of mounting holes but the idea was that by switching out the insert inside the transom riser I could adjust the angle. I plan to remove the sacrificial plate and the aluminum motor mount pad but keep the aluminum bar I have on top of the transom. The yellow parts are two rubber pads that I would use to shim the remaining space. I will definitely check to make sure its not too thick. Thanks!
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Old 26 June 2014, 16:39   #29
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I wouldn't use anything compressible. HDPE maybe. One problem I can see is matching standard rectangular pipe stock usually 1.5" or 2" to something lapping 40mm transom + thickness of pads. Guess you could shim 1.5 rectangular with with 1/8-1/4 plate.

I doubt you would adjust it much later. In my case I just cut three 1/2" HDPE plates of desired width + one extra of needed thickness on table saw.
If riser is too tall (unlikely) you can always just cut those down.
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Old 26 June 2014, 17:40   #30
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I think I'll skip the adjustability aspect. In the unlikely event I can always as you say trim it later.
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