Tell me about these motor mounts
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Tell me about these motor mounts

  1. #1
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    Default Tell me about these motor mounts

    I don't really like the looks of them. They don't seem strong, in the one already looks bent.

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  3. #2
    Senior Member jetboatperformance's Avatar
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    That's part your basic Jet Boat 3 point mount system,that style/type mounts were routinely used in production boats for years. The weight of a average Big block puts a bit of strain on stringers and motor boxes over time with them , they are simple to install and reinstall, Ok for lower HP applications , not as dependable or as strong as a traditional 4 point cast mount or rail mount kit

  4. #3
    Senior Member hihosilver's Avatar
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    looks like they are sagging , road hard put away wet!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

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    Senior Member jetjunky's Avatar
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    certainly insufficient currently for your h.p desires. It could be modified/restructured to better handle your your desired h.p but prolly still a weak link. While the 4 pt. mount system is a rather significant effort to install is fully up to the task of your h.p goals hence the commonality of them.
    Last edited by jetjunky; 12-26-2015 at 11:55 AM.

  7. #5
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    The crank centerline on a four point rail mount ....is it equal with th top of the rails?

  8. #6
    Senior Member jetboatperformance's Avatar
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    Crank centerline, pump center line and driveline alignment are all relative to correct installation. Rail mount kits aren't neccesarily "plug and play" the are intentionally cut "big" to allow for custom fitting ,installation varies from boat to boat and stringer height , pump installation , drive line OAL, hull design etc all enter in, it helps to have access to a band saw, drill press, angle finder/inclinometer/protractor and a mock block really makes things simpler

  9. #7
    Senior Member jetjunky's Avatar
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    no.... it's parallel to the pump shaft w/1-2 degree vertical offset for best u-joint wear/perf. There was a really good thread on here about a year ago regarding this. Elevating the motor allows for max oil pan clearance @ the forward intake bolts when running a deep pan (8" +/-), which you should be if your not..... (note: simple and fun just flew out the window. haha) I'll see if I can find the link, should be in my sub'd threads folder.

  10. #8
    Senior Member jetjunky's Avatar
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    Default drive line angle, engine placement

    Here you go, this should help significantly... I hope..... http://www.performanceboats.com/jet-...alignment.html

    After studying this I ended up redoing mine because being close wasn't good enough for me. Now it's dead nuts, rather tedious but worth the effort and peace of mind. I built a nice 4 point adjustment tool that mounts to the front and rear main caps and locates off the top of the stringers. Allows me to precisely set motor height, angle etc., leave motor in place, remove the f/r templates to obtain perfect fitment, then build alum. plates off templates, then fine tune them to perf. fitment (thicker material requires specific shaping). My motor plates rest on top of the stringers and bolt to the stringers with angle brackets. (as seen on most circle race boats) The foundation of the drive system/motor placement is the pump intake adapter placement. Every boat is different be it ever so slightly or wayyy diff, regardless of model/yr. etc.

  11. #9
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    I can find square off of the crank flange and compare to the bearing retainer on the pump? vertical may be more difficult?

  12. #10
    Senior Member jetjunky's Avatar
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    good luck with that. lol you may find it much more accurate and easier to pull off the exit side bowl flange on a G style bowl.

  13. #11
    Senior Member jetjunky's Avatar
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    here's a couple pics I found from when I was setting mine up. had to dig a while to find them. This may be of help I dunno.
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    Last edited by jetjunky; 01-28-2016 at 09:14 AM.

  14. #12
    Senior Member jetjunky's Avatar
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    Default motor placement jig

    Here's a couple pics of the motor locating jig I built after some other craftier p.b. v-drive rigger dude posted some pics of theirs. It's really pretty simple to build and works very well, super fine tuning of angles, heights etc. It's a piece of angle iron that bolts to the f/r main cap bolts with welded tube/plate assem. attached to raise up to the stringer tops. The solid alum. bushings that the alum. tube runs thru to align motor to pump shaft I had machined to fit the f/r main crank journals (w/o bearing shells) and accept the alum tube. At the rear is another sleeve tube with the id that just slips onto/over the pump shaft splines. When the sleeve tube easily slips over the pump shaft you know it's pretty darn straight with the pump. That sets the horizontal dimensions from motor center line to stringers. With that established you can then start cranking the 4 corner screw adjusters to set the correct height and angle. I hope this helps.
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  15. #13
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    I was told the pump is 4deg angle up towards motor. I have 3 questions: from above motor and pump are exactly inline? From a side perspective, the angle of the motor should be the same as jet shaft (4deg or whatever)?

    Time well wasted

  16. #14
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    The last question is should motor be a little higher or lower in the mounts to give the u joint a slight offset? Kinda like trans output shaft and pinion in a car?

    Time well wasted

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