Seapup, if the purpose of moving the rudders back is so that they'll clear your rap-around deck when you pull them up, why not just leave a slot in the deck that the rudders can pull up through? Much easier, and that will keep the motor from flopping over when trailering.
Thanks for the suggestion. I considered the notch idea when I made the deck, but you need to make it a V to allow for turning with rudders up which greatly limits the useable space. Moving the whole rudder assembly back would realign the steering to stock and provide a support for a larger deck as well as steering linkage room under the deck. I was considering bolting up a section of 6" square aluminum tube on each side of the transom like a jackplate for the rudders, but will probably put that on hold, which Ill vent why in a minute.
How did the jack plates and set back work out for everybody ? I like the idea of having extra room in the back but not if it tears my transom out.... I hope to hear it worked out really well !
So far so good, I really like it. There is substantially more room getting around the larger motor now than with the smaller motor before. With multiple variables I can't say what is responsible for trim, but a tiny amount makes a huge difference. Before it didn't do much of anything. I think the extra leverage, hydrofoil, large prop and empty boat are all acting right now. In the water the motor acts like its fixed solid and the boat levers off it. Trim a little and the bow goes right up or down accordingly.
The transom
seems to be holding up fine. There are no stress cracks and nothing has shifted or loosened back there. I was a little rough on it hoping if the transom was going to crack it would happen before the season. The plate spreads the load out more than most outer plates people are using so in my uneducated non engineer analysis I think it will be OK. So far I am glad I went with it. Thursday was the first time out, wind was 15-20 and waves were 3-4 at 7 seconds according to NDBC for where I was. I had a bare empty boat with just 2 people and 4 gal of gas. Being empty the 4 blade 13.75 inch was under propped and revved over 6k a little past 3/4 throttle empty. As far as the jackplate something to keep in mind, for every inch of setback you are supposed to raise the motor about .5 inch to compensate for the offset angle and water lifting behind the stern. I had the cav plate a little above the stern and the motor was buried. I moved it up about 2" (back where it was in the first picture) when I got home and will try again.
As others have said the difference with the larger motor is quite a change. Docking put it in gear and it moves, no more revving to change direction. 1700rpm was 7mph both full and empty ballast. At 3k ran 14mph full ballast, same as honda wot, but sounded like honda at 2k. 3/4 throttle full ballast (didn't check rpms as we were crashing into/against waves hard) was 24mph and much faster than necessary. Kate asked if there were pirates she had missed and I was trying to outrun as she was soaked. Emptied ballast and shot over a few waves running with the wind and max on the gps said 28 mph. From the sound of the motor (or lack of sound) I guessed I was at about 4k so was very surprised to see it at 6k. With the old motor the waves would have been pushing me around and trying to keep a straight line would have been difficult. With this I just held a straight line and powered over them vs being pushed. So far I am very happy with the choice.
After washing the boat up from testing it was late so I left it in the driveway. Friday I got a ticket from the city saying I had to move the boat. The neighbor called first thing Friday. I had the same issues both last spring and again in the fall while working on it. City code says it can't be in your driveway more than 24 hours. They only enforce it if a neighbor complains. I live a half mile from the ocean and there is a boat on every block, normally its a non existent law. I get the one cranky old spinster nextdoor that has a nothing better to do. In past she has reported "dangerous trees" and "diverted runoff" (both dismissed). Officer was nice at least. I asked how long it had to be out of the driveway before it could return so I could work on it. Could I just drag it around the block? He told me to submit a written letter saying I couldn't move it without repairs and he would grant me an extension. So I am just going to finish my existing projects and put it in the water for the season.
Now I need the rain to stop so I can finish my interior, changing things up a bit. Here is a pic since I know how holes in fiberglass make some people cringe
This was about halfway through the cutting.