292 SR-1 Shorties and Extension Boxes
03-21-2016, 07:29 PM
#12
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So are you putting the boxes and shorties on at the same time? It would give you more data to do one at a time, but that may involve more work I am not too familiar with the process of installing boxes.
It would seem that with the setback plus the extension boxes, they will cancel each other out and you may end up at the same relative prop shaft height?
It would seem that with the setback plus the extension boxes, they will cancel each other out and you may end up at the same relative prop shaft height?
03-21-2016, 10:31 PM
#13
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Yes this is all getting done at the same time. Time is limited and this project is a fair amount of work. Ideally it would be nice to test each thing out and see what the results are, but unfortunately I don't have the time to do that. Plus my uppers are not built yet, so that would push me back even further. I did install the boxes on today and it really is a nice set up.
As for the boxes canceling out the shorty's, the gimbles appear to be the same height as they were prior. Merc has the Gimble mounted around 1 to 1 1/4" higher than the mounting location of the stock location. Once mounted, due to the transom angle they are at the same height. Also remember these are only 7" deep. From what I've read with a 12" box you add 1" of prop shaft depth, so with 7" I should lose around 5/8" of effective prop height.
As for the boxes canceling out the shorty's, the gimbles appear to be the same height as they were prior. Merc has the Gimble mounted around 1 to 1 1/4" higher than the mounting location of the stock location. Once mounted, due to the transom angle they are at the same height. Also remember these are only 7" deep. From what I've read with a 12" box you add 1" of prop shaft depth, so with 7" I should lose around 5/8" of effective prop height.
03-21-2016, 10:36 PM
#14
03-22-2016, 04:38 PM
#17
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I'm running modified 420's. They are basically HP 450's now with 741 cams. I'm running dry to the tip Gil manifolds and without the platform on they're loud, if I remember right 91 db's at idle with one engine running. With the drilled platform it's quieter, but I forget how much; however it quite a bit louder than with he silent thunder complete.
It would have been nice to have done testing with each step of the project but with limited time it just isn't possible. If anyone is thinking about external steering- look for an ITS setup. Yes they're expensive but it fits perfectly, and best of all you don't have to modify a thing. Soon we will see if there are any speed gains- for my sake I sure hope there is.
It would have been nice to have done testing with each step of the project but with limited time it just isn't possible. If anyone is thinking about external steering- look for an ITS setup. Yes they're expensive but it fits perfectly, and best of all you don't have to modify a thing. Soon we will see if there are any speed gains- for my sake I sure hope there is.
03-22-2016, 04:54 PM
#18
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So, the Merc extension boxes raise the gimbal 1", then the shorties raise the prop shaft another 2.5" for a total raising of the prop shaft of 3.5"?
Then the setback is the equivalent of lowering the prop shaft 5/8" lower?
Then the setback is the equivalent of lowering the prop shaft 5/8" lower?
03-22-2016, 06:22 PM
#19
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No- The ITS box mounts the gimble about 1" higher. Once mounted to the boat, it appears to be in the same position. I'm sure this is due to my transom angle. I don't have any drives to mount up right now so it's really hard to tell exactly where things are. The shorties are 2" less. My propshafts should be at 5" below the transom, they started at 7" below. Once I get the outdrives on, I can remeasure and see where I ended up.
The 5/8" loss will come due to the water coming up from under the hull. That is all theoretical though. When all is said and done I should gain 2" of height to my prop shafts.
The 5/8" loss will come due to the water coming up from under the hull. That is all theoretical though. When all is said and done I should gain 2" of height to my prop shafts.
03-22-2016, 08:08 PM
#20
Should have bought the 5 inch extension box for the ITS drive and then use the long IMCO input shaft. Gets you all o]the benefits of a 12' box. That boat could probably use it.
