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  1. #1

    Default Wont throttle up all the waty

    I have a 1991 Johnson 48 SPL J48ESLEIM, it is a new to me motor. It starts up easily, idles smooth and sounds great. I took it out for the first time started it up and let it warm up for about ten minutes and eased away from the boat ramp. When I tried to go to full throttle it didn't seem to power up all the way. I do not have a tach on it yet, waiting on a tiny tach to come in. Sitting in the middle of the lake, I put it back in neutral, and used the high idle and the motor reved up real high. I have the type of control to where you pull out the lever and move it forward to increase the idle. I put it back in gear and it still does not seem to rev as high in gear as it does in neutral. Using a GPS the highest speed I got was 5mph. I drove the boat around for an hour or so at different levels of throttle hoping it would clear something out but it never got better.

    I don't know if the linkages need to be adjusted or if something else needs to be done. There does seem to be excess travel in the throttle control. When shifting from neutral to forward, I barely have to move the lever. After it engages forward I have to move the lever more than half way before it starts to power up. The range of lever movement from when it starts to rev up to when the lever bottoms out does not seem to be very much. I did a spark test and both jump a 1/2 gap, the compression on the top cylinder is 130 and the bottom is 125.

    Any suggestions as to where I need to start?

  2. #2
    Join Date
    Jul 2014
    Location
    Buffalo, NY
    Posts
    77

    Default Re: Wont throttle up all the waty

    I'd start by adjusting your throttle linkage that doesn't sound right to me.

  3. #3
    Join Date
    Sep 2010
    Location
    ontario
    Posts
    15,360

    Default Re: Wont throttle up all the waty

    Ruptured diaphragm in fuel pump.-----Sheared flywheel key.----Bad sparkplug.-----Reed valve stuck open.-----Bad lower crank seal.-----Linkage off one carburetor.----Timer base sticking.----Plugged highspeed jet in the carburetor are all possibilities.----Yes they will rev up in neutral on one of 2 cylinders , that means nothing.

  4. #4
    Join Date
    Nov 2005
    Location
    Mt. Zion, Illinois,
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    770

    Default Re: Wont throttle up all the waty

    Easy test: remove the engine cover and take the front off the air box. Now, with the engine OFF look at the butterflies in the carbs. Are they completely closed? If yes, now put the control in forward gear and move the handle to full throttle position. Are both butterflies now completely open? If one is totally open but the other is not you have a linkage problem. If both do not go fully open it could be a Problem with the linkage connection to the throttle cable, or you could have a throttle cable that is rusted up. It could also be an installer issue. Maybe someone messed with the cables and didn’t know how to adjust them. Another option is a kink in the cable. Sometimes folks get cables that are too long and just loop up the extra length. If that gets too tight it can kink the cable.

    If none of that is true it could be as simple as plugged high speed circuits in your carb(s) or one of the many other possibilities racerone suggested.

    The throttle test test I described is easy. Do that first then report back.

    KJ

  5. #5

    Default Re: Wont throttle up all the waty

    KJ,

    I did your recommended test. With the control lever in the neutral position, both butterflies were closed. When I mo ed the lever to the full throttle position both butterflies were totally open.

    There is not a gasket between the air box cover and the air box and one of the screws is missing. Will this cause any problems?

  6. #6
    Join Date
    Sep 2010
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    ontario
    Posts
    15,360

    Default Re: Wont throttle up all the waty

    That missing gasket is NOT your problem.---Nor is the missing screw.

  7. #7
    Join Date
    Jul 2014
    Location
    Buffalo, NY
    Posts
    77

    Default Re: Wont throttle up all the waty

    Maybe some idiot (myself) rebuilt your carbs and didn't put all the required parts back in...?

    Sorry couldn't help it...

  8. #8

    Default Re: Wont throttle up all the waty

    I have ordered 2 carb rebuild kits, should be here in a few days. Ill do that and see what difference it makes.

    In the repair manual it recommends Champion QL78C plugs. The ones in the motor were NGK B7HS10. Is that a problem? I looked at a cross reference comparison and B7HS10 does not cross to QL78C.

  9. #9
    Join Date
    Nov 2005
    Location
    Mt. Zion, Illinois,
    Posts
    770

    Default Re: Wont throttle up all the waty

    You should only use OEM spec Champion marine spark plugs. NGK makes a great spark plug, but not for Johnson/Evinrude applications. Switch to the proper plugs and try again.

    KJ

  10. #10
    Join Date
    Apr 2016
    Location
    barnegat NJ
    Posts
    3,143

    Default Re: Wont throttle up all the waty

    check the timer base,is it advancing with throttle application ?

  11. #11

    Default Re: Wont throttle up all the waty

    It is supposed to rain all weekend here, I will replace the spark plugs and take it out Monday and see where that gets me. When the carb kits get here I will put them in and follow up here/

  12. #12
    Join Date
    Nov 2005
    Location
    Mt. Zion, Illinois,
    Posts
    770

    Default Re: Wont throttle up all the waty

    Quote Originally Posted by johnnygjr View Post
    check the timer base,is it advancing with throttle application ?
    Good suggestion here.

  13. #13
    Join Date
    Apr 2016
    Location
    barnegat NJ
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    3,143

    Default Re: Wont throttle up all the waty

    Kevinj where is MT.Zion, I was born in evergreen park, I believe a suburb in Chicago.

  14. #14
    Join Date
    Nov 2005
    Location
    Mt. Zion, Illinois,
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    770

    Default Re: Wont throttle up all the waty

    3 hours south of Chi town, just outside Decatur.

  15. #15

    Default Re: Wont throttle up all the waty

    Quote Originally Posted by johnnygjr View Post
    check the timer base,is it advancing with throttle application ?
    is the timer base the same as the spark control rod?

  16. #16

    Default Re: Wont throttle up all the waty

    Replaced spark plugs and went through both carbs with rebuild kits. Motor fired right up and ran great on muffs. Took it out to the lake and it ran great. There was approximately 3/16" difference in the length between the NGKs and the Champion, with the Champion being the longer of the two. Rhe carbs looked pretty clean with onlly a little trash in the lower carb. Handheld GPS showed top speed at 27mph.

    On another note, I had a tiny tach hooked to the #1 spark plug and at idle it showed 2300 rpms at full throttle it showed 10900 rpm. Not too sure the tiny tach was working correctly. When the motor was at idle it didnt sound like it was running that high, and the same at full throttle. Any ideas about tiny tachs?

  17. #17
    Join Date
    Sep 2010
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    ontario
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    Default Re: Wont throttle up all the waty

    Is there a setting for a 2 stroke motor on that tach ?

  18. #18

    Default Re: Wont throttle up all the waty

    Not sure, there weren't any instructions with the tach. I think they forgot to include them.

  19. #19

    Default Re: Wont throttle up all the waty

    If I were to put on a regular tach, what kind would I need? How do I tell the how many poles or pulses?

  20. #20
    Join Date
    Apr 2016
    Location
    barnegat NJ
    Posts
    3,143

    Default Re: Wont throttle up all the waty

    half those tach readings 1150 and5450 REad post#17

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