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  1. #1

    Need help, advise, support

    just bought a 94-750st with a motor that is gaulded, I found a 97 750ss motor with 150-150 comp, the st has single carb the ss looked to have dual, ? is will the ss motor fit and hook up in the 94 st body and if so do I need to get any other parts from the seller? Also after removing the motor mount bolts will the engine separate from the drive shaft or does the shaft screw to the crank?
    motor is about 75 miles away and I just wanted to make sure before I drop a few $$ and it be wrong.

    Thank you for your time and help


  2. #2
    demian5's Avatar
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    The motor should work. It isn't bolted to the drive shaft, it has a rubber coupler. Should be a stright up swap if you swap intake exhaust etc... They used those motors forever.

  3. #3
    Quote Originally Posted by demian5 View Post
    The motor should work. It isn't bolted to the drive shaft, it has a rubber coupler. Should be a stright up swap if you swap intake exhaust etc... They used those motors forever.
    Thank you, I see that there are 2 different thread sizes on the end of the crank that the coupler screws on so I'll have to make sure to get it. I've undone the exh on the old one and a few hoses, what is the easiest way to get the motor out of this cramped space? Any shortcuts or words of wisdom?

    Thanks again

  4. #4
    steve45's Avatar
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    To remove the engine, remove the flame arrestor, then the carb. Remove the exhaust system, unplug all wiring, remove water lines, disconnect & plug fuel & oil lines.

    Make a couple of angle brackets with two holes in each one. One hole fits over the spark plug threads, one hole is used for a chain or rope. Tie the brackets together with the chain or rope, then put then on top of the cylinder head and screw the spark plugs through them into the heads. (No need to tighten). You now have a 'lifting eye' that you can hook onto with a hoist or crane to lift the engine out.

    Reverse the procedure for the new engine. Twin carbs will have to be removed for the install. After you get the engine in, re-install the carbs, exhaust, fuel, oil & water hoses, etc. Make sure you have oil in all the oil lines and bleed air from the pump via the bleeder screw.

    I wasn't aware that there were two different crank couplings. When you bolt the engine down, you'll have to check for proper alignment of the coupling. A service manual will tell you how to do that, but basically, you can remove the spark plugs and spin the engine over and watch for misalignment. If the coupling halves don't line up very well, you may have to put shims under the engine mount or loosen, clean, re-glue and re-tighten the driveshaft bearing support.

  5. #5
    Thanks,
    Got engine in, hooked up, and when I spin it without plugs dreaded water is squirting out, so I'm going to pull the exh elbow off and make sure everything is sealed. Any other places to check or look?

  6. #6
    Well stupid me ....I turned the water on first got her running and she pops, spits, sputters a little so I topped the tank off with premix and seafoam. Hopefully I can put her in the water tomorrow on the trailer and test it out.

  7. #7
    steve45's Avatar
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    Don't leave water in the engine! You need to run it on the hose for a few minutes to get the water out of the crankcase. If not, the bearings will rust in as little as one day.

  8. #8
    I took the plugs out and opened the crank vent spun it over to expell the water, then started her for a few sec to push the water out. I turned the hose on without even thinking...
    How can I check the exhaust to see if it has a leak? Also there are some exhaust fumes in the engine bay.
    Thanks again, and the kids thank you, it's for them.

  9. #9
    Took her to the lake and ran fair, had it richened up pretty good, rode 30-40 mins, cut it off and then nothing just a click..starter went out, out her home and took starter off donor motor and it's back alive.
    ?? where is the pisser on these? I did not see the telltale water spout like the others, the vent on the side of the hull is clear.
    Thanks,

  10. #10
    Did you install the ss impeller on your st as well?
    If the ss has a dual carbs, you should have to match the power output and to get the best perf out ot it.

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