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Thread: finally ran dry ground

  1. #1
    Member yamahaulerG1's Avatar
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    finally ran dry ground

    I'm still running the generac direct drive with the ultra prop. I went back to the stock carb and after lots of test rides and tuning I'm getting close to having it right. My prop was 53.5" 12 degrees and i chipped the edges so i cut them back to 52" and if i screw in the pilot jet 1/4 turn rpms go up to 3000 but it hesitates more when I stomp on the gas. If I turn the pilot jet out a 1/4 the hesitation goes away but i loose rpms I'm hoping a smaller jet might help. When I was adjusting it today it started running dry at 3000 rpm. My next step is a bigger cam i found the part number to a factory performance cam from generac. Here is a link to a rough video of my boat running dry ground. I was standing next to the boat and then jumped in when i realized it was going to move. https://youtu.be/icIuHrBDLB4
    Last edited by yamahaulerG1; 03-04-2018 at 07:55 PM.

  2. #2
    Super Moderator Corky's Avatar
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    Re: finally ran dry ground

    I bet that was a surprise !! ...How much more projected HP will you get with the hotter cam ?? Looks like you're right there for running dry the cam might do the trick...

    Aluminum .120 14' X 76" hull
    Teledyne 4a084-4 engine
    Circle S 1.69:1 reduction
    67" Whirlwind "Razor X" prop



  3. #3
    Member yamahaulerG1's Avatar
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    Re: finally ran dry ground

    Yes it was very surprising. I won an eBay auction for three mower carbs for $25 and the jets were 150 main and 50 pilot mine was 125 main and 42 pilot. I also found the emulsion tube from a 27hp that helped with the low end acceleration. I swapped them all and seems to run better but I can't test it now because I noticed my motor stand is cracked badly. So no more rides for a while until I fix that. My motor is from the 16kw, The cam is from the 20kw and 22kw generator the only thing they changed was the cam and they made a longer stroke with shorter rod changing it from 992cc to 999cc and then a thicker head gasket to keep compression the same. So I'm not sure of the gain i will get from the cam but I'm sure it will be stronger and it only cost $75 to find out. The cam part number is 0G7974 and here is a pic of the difference in the emulsion tubes.
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  4. #4
    Super Moderator Corky's Avatar
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    Re: finally ran dry ground

    At least you have some parts to experiment with....It's easy to drill them out too far....Some will solder those emulsion tube holes closed and gently drill/relocate them until you get what you need..Every mod to a small engine has a bigger affect on the rest of the tuning compared to a larger displacement engine...Add in the outside elements,bad fuel, and general wear and tear it's almost a full time ordeal keeping them going for our application...

    Aluminum .120 14' X 76" hull
    Teledyne 4a084-4 engine
    Circle S 1.69:1 reduction
    67" Whirlwind "Razor X" prop



  5. #5
    Member yamahaulerG1's Avatar
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    Re: finally ran dry ground

    I just ordered the cam today. I'll install it when I remove the motor to build a new motor stand. I plan on raising it up so I can swing a 60" prop in the future. Also I found out the cam part number is actually 0G79740SRV, the stroker crank is 0G5001ESRV cost 126, and the matching connecting rod 0J8968 cost 21. Just in case someone ever wants to build one.

  6. #6
    Member yamahaulerG1's Avatar
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    Re: finally ran dry ground

    Update: The torque and roughness of a few dry runs and the motor stand cracked from not supporting it directly under the torque side of the engine so it's been sitting for some time. I was able to find time to patch it up this weekend. Test drove it yesterday and it's getting 3020rpm but running too rich one side is black smoke and the other side keeps fouling the plug. So I ordered one of the wideband a/r kits to help tune it. Now I'm building a new motor for it using the motor with the broken crank. Ordered 1-7/16" straight shaft and compared the new cam with old and the new cam has 1mm more lift and i plan on smoothing out the sharp edges in the ports.
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    Last edited by yamahaulerG1; 07-30-2018 at 09:52 PM.

  7. #7
    Super Moderator Corky's Avatar
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    Re: finally ran dry ground

    Yep they call that work hardening.....A little more support here and there...Remember, don't overdo the head porting just smooth out the sharp edges and port match..If you go too far you'll lose your bottom end response from less velocity at low RPMS...It's a fine line between just right and too much...The general rule is not to modify the "short side" of the port in most applications...

    Aluminum .120 14' X 76" hull
    Teledyne 4a084-4 engine
    Circle S 1.69:1 reduction
    67" Whirlwind "Razor X" prop



  8. #8
    Member yamahaulerG1's Avatar
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    Re: finally ran dry ground

    I'm only planning on rounding out that sharp 90 inside the ports not really enlarging them any. I guess my a/f ratio gauge at a very good price was to good to be true eBay told me I bought it from a hacked account. So I'll still be guessing at the jet sizes but I know they are too big right now. But it will rev up quick with no hesitation when the plugs are clean.

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    Re: finally ran dry ground

    Man looking good i got the same engine i try to modify to run on mine part number helps alot i just noticed you runing a sole clone on jours were you get the intake

  10. #10
    Member yamahaulerG1's Avatar
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    Re: finally ran dry ground

    I have been using the stock carb that I enlarged with a deburring bit. I still haven't found the right sized jets yet but I'm close and with the right jets this carb has a good response.
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  11. #11
    Member yamahaulerG1's Avatar
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    Re: finally ran dry ground

    I've been trying different jets with the stock carb but if I hit the gas hard from idle it will stall. Plus I'm making max rpm at 3/4 throttle nothing changes from 3/4 to full throttle. Thinking because this carb was made to turn the motor 3600rpm so I thought a smaller carb might help by raising the air speed in the carb. I switched to a 32mm constant velocity carb and after a day of swapping jets it's running decent. My rpms didn't change much but it accelerates with no problem, doesn't stall no matter how fast I hit the throttle. I'm thinking of trying a few different setups if I find time. Here is a video of it running with the new carb. https://youtu.be/wIQmhsOQC7k
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  12. #12
    Super Moderator Corky's Avatar
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    Re: finally ran dry ground

    Wow, show off.......In and out of the water like it was just meant to be...While it looks to be an engineering feat in the pic it sure runs well in the real world...Nice job...

    Aluminum .120 14' X 76" hull
    Teledyne 4a084-4 engine
    Circle S 1.69:1 reduction
    67" Whirlwind "Razor X" prop



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