1956 Johnson 30 hp won’t accelerate boat up on plane!

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    Jeffrey Durst

    US Member - 1 Year
    Replies: 21
    Topics: 5
    #221164

    I have a ’56 Johnson 30 hp Javelin that I recently purchased. The motor is in perfect condition and appears to have been completely restored. Before I started it up I removed all of the fuel lines and rebuilt the carburetor to make sure there wouldn’t be any fuel issues. It starts easily and idels nicely at slow and mid speed. However the throttle lever stops short of getting the motor up to a fast enough speed to put the boat up on plane. It seems like there is something that is not allowing the throttle cable to advance the motor to the full open position. I have adjusted the cable to no avail. Can someone suggest some ideas of what I should check in order to fix the problem? Thanks!!!

    frankr
    frankr


    Replies: 5408
    Topics: 48
    #221166

    First step is to disconnect the cable from the motor, then make sure the linkages and stuff is correct on the motor itself. This includes syncing the cruise throttle rod. If you don’t know how to do that, get back with us. When everything is correct, full throttle position will be right. NOW connect the cable and see if it will take the throttle to wide-open position. If it won’t, repair whatever is wrong with the remote control/cable. Always adjust the control to fit the motor, never adjust the motor to fit the control

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    outbdnut2

    US Member - 2 Years
    Replies: 1355
    Topics: 70
    #221180

    Take off the carb intake silencer so you can see past the choke to the carb’s throttle valve and, with the motor not running, put it in forward gear and advance the throttle to maximum. Look in and see if the throttle valve is fully horizontal (wide open). If it’s not, examine remote cables and all linkage to the carb to find out what is restricting it, as others have suggested. The problem could be incorrect mesh of the gearing inside the remote control box.

    If your boat is big and heavy, you may need a smaller pitch prop to plane it off. You also may need to drop the trim pin to a lower setting. Weight distribution in the boat can cause it not to plane if most of the weight is at the rear.
    Dave

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    Jeffrey Durst

    US Member - 1 Year
    Replies: 21
    Topics: 5
    #221336

    Okay, I took the throttle cable loose from the motor and advanced it to the “fast” setting on the motor and checked the throttle valve in the carburetor and it was fully horizontal making me think that everything is okay there. I adjusted the cable connection and thought all was good there but when I put it in the lake today it was doing the same thing again. How do I “synch the cruise throttle rod?”

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    dave-bernard

    US Member - 2 Years
    Replies: 1247
    Topics: 17
    #221337

    with the cable hooked up. does the carb open all the way. if it does then the problem is else where. the prop first would be my guess.

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    outbdnut2

    US Member - 2 Years
    Replies: 1355
    Topics: 70
    #221343

    Do you know of it’s running on both cylinders – take out your spark plugs and look at them. If one isn’t firing, it will be wet compared to the other one.
    Dave

    • This reply was modified 6 days, 10 hours ago by Avataroutbdnut2.
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    Jeffrey Durst

    US Member - 1 Year
    Replies: 21
    Topics: 5
    #221346

    No I don’t think so. I’m pretty sure the problem is with the throttle cable where it attaches to the motor and I’ve tried adjusting it but it still doesn’t work right. I don’t see anything in the manual about how to properly adjust this connection. When I have the cable disconnected from the motor there seems to be plenty extension and contraction but when I hook it back up and use the control lever to fully accelerate it doesn’t push the throttle mechanism on the motor far enough to get full acceleration. Any further suggestions?

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    Jeffrey Durst

    US Member - 1 Year
    Replies: 21
    Topics: 5
    #221349

    It seems like the motor is firing on both cylinders but I’ll pull the plugs tomorrow morning and check that out!

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    billw

    US Member - 2 Years
    Replies: 1343
    Topics: 40
    #221358

    If the throttle valve is opening all the way, my money is that you’re only running on one cylinder. It is surprising how deceptively well some engines….like yours…will run, on just one cylinder, if you don’t have an experienced ear for it. You need to do a compression and spark test, as basic first steps. I believe you should have at least 100 pounds compression (Bigtwin/RD fans, correct me if I am wrong on that) and the spark should be nice and blue, being able to jump at least a 1/4″ in open air. If the ignition hasn’t been serviced in awhile, that should probably be done, regardless. The term “completely restored” is probably one of the most vague, misinterpreted terms in all of mechanics. It all depends on who did what, and when.

    Long live American manufacturing!

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    Jeffrey Durst

    US Member - 1 Year
    Replies: 21
    Topics: 5
    #221364

    Okay, I removed both spark plugs and they were both dry. I did a compression test and both cylinders are reading 120 lbs. Also checked the spark and I’m getting good spark on both. I checked the control box and everything there seems to be in good order. Now I’m back to tinkering with the throttle linkages. To answer Dave’s earlier question the boat is a 15 footer and weighs 520 lbs. The original 1956 Wagemaker brochure for the boat shows this same Johnson 30 hp motor mounted on the back so I think I’m within the correct weight limit for this motor. The propeller is an original 3 blade type and I have the trim pin set to the lowest setting. At this point I am even more convinced that it’s something to do with the throttle linkages but I’m fairly new at this and have never messed with any of these linkages before. You guys help is greatly appreciated…

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    fleetwin

    US Member - 2 Years
    Replies: 3530
    Topics: 46
    #221365

    Post some pictures of the engine in gear with the throttle open completely, perhaps someone will spot something…..Take pictures from both sides and from the front of the carb….
    Perhaps you can post a video of the engine running on the boat if possible…

    Tubs
    Tubs

    US Member - 1 Year
    Replies: 3299
    Topics: 135
    #221370

    You're only as smart as the person you're talking to.

    • This reply was modified 5 days, 19 hours ago by TubsTubs.
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    outbdnut2

    US Member - 2 Years
    Replies: 1355
    Topics: 70
    #221378

    Have you taken the remote throttle lever box apart to see that the gear teeth on the throttle lever are properly orientated on the straight toothed plastic piece on the end of the throttle cable? If it’s a couple teeth off, it won’t advance the cable all the way.
    Dave

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    Jeffrey Durst

    US Member - 1 Year
    Replies: 21
    Topics: 5
    #221382

    Hey Dave, everything seems to be in good order inside the remote shift box. I think I may have figured out what the issue was. I think when I rebuilt the carburetor I may have put the
    stop adjustment screw that goes on the little rod that goes from throttle rod to the carburetor in the wrong place. Now when I push the remote throttle lever forward to maximum the throttle valve is in the wide open position and seems to stay there. I was going to test it out on the water today but it started raining here. We really need the rain so I can’t complain too much. I’ll let you guys know how it goes when I get it in the water!

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    joecb

    US Member - 2 Years
    Replies: 408
    Topics: 61
    #221396

    What Tubs said …. have we checked for proper carb to mag plate cync? Full mag advance is essential for full speed operation.

    Joe B

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