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Author Topic:   40 Johnson bogs down - ???
DamselFly posted 06-10-2003 12:31 AM ET (US)   Profile for DamselFly   Send Email to DamselFly  
I've got a 40 Johnson VRO on my 13. I've had it out twice so far this year, and both times it's given me problems so bad, I had to limp back to the dock. I've got the VRO disconnected and I premix. The motor will start out ok, and I can get full throttle no problem. Then, all of a sudden, the motor bogs down to no-wake speeds, even with the throttle pegged all the way. If you drop down to idle, it idles fine. If you throttle up, it does okay to just off idle, then bogs down again, even with the throttle pegged again. It did this to me once last year as well, when I was running in the inlet with some major swell, kinda spooked me! I thought the motor was gonna die in the inlet. Thankfully, these past 2 times haven't been too far from the dock. Any ideas on what to try and fix this? I just had it in the shop this spring and had the lower unit oil changed and the carbs cleaned. Thanks in advance for any info!
UnderDog posted 06-10-2003 12:40 AM ET (US)     Profile for UnderDog  Send Email to UnderDog     
Hello Damselfly, what you might look for corosion under the coils, make sure they are getting a good ground, also check your spark plug wires and plugs, those are basic things I would check, I had a 120 that was doing the same thing and that fixed it.


Bigshot posted 06-10-2003 10:47 AM ET (US)     Profile for Bigshot  Send Email to Bigshot     
Check all your fuel ines and connections for leaks. you are sucking air somewhere and shop may have not tightened a clamp etc. Next time t bogs push the key in and see if she goes. if so then fuel, if not then spark.
DamselFly posted 06-10-2003 01:29 PM ET (US)     Profile for DamselFly  Send Email to DamselFly     

You mean push in the key, like I do when I'm starting the motor? What does this do? I'm thinking it squirts some fuel in the carbs, right?

UnderDog posted 06-10-2003 01:59 PM ET (US)     Profile for UnderDog  Send Email to UnderDog     
damselfly, what bigshot suggested is called the electric choke give it a try..


Duckin Whalers posted 06-10-2003 03:09 PM ET (US)     Profile for Duckin Whalers  Send Email to Duckin Whalers     
I had a similar problem although, I found the problem not to be the motor. I was getting fuel starvation becuase of inadeqate venting in the fuel tank. Known as "Vapor Lock" I bought a new vented gas cap at the auto parts store and have not had the problem again. Might be worth a try instead of a mechanic. My friend just bought a new aluminum boat with a 50 Yammaha and called me on his cell when he was out on the water. The Yammaha started idled and ran ok until just after full throttle. Then it would pretty much die. I had him look at his tanks(he has plastic) and he he said they were "shrunken" I had him loosen the vent valve, they popped back to shape and the motor ran fine. just thought it was worth a try.
Bigshot posted 06-10-2003 03:31 PM ET (US)     Profile for Bigshot  Send Email to Bigshot     
Ok I'll start from scratch:

To test fuel starvation you need to try and pump the bulb before you start the engine. When it gets hard, remove the cowl and squeeze it again a few times and see if you have any leaks. Don't death grip it, just keep squeezing gently. If good there then drop the pig in the water and go out. Have a friend drive. Once it starts bogging, squeeze the bulb again. If it was soft and then gets hard and the engine picks back up, you have a problem with the tank/checkvalve/bulb/hose/vent. Start there and get back to us.

If (again on the water) she bogs but fuel bulb is hard, remove cowl and flame arrestor assembly from in front of carbs. have a squirt bottle with pre-mix in it(if not oil-injected) and while bogging squirt some fuel in each carb throat. If she again picks up you are starving from fuel in whatever carb reacts. If both react then it is main fuel supply. If engine bogs further when fuel is sprayed, then electrical. You may have a coil that goes out when hot or a powerpack acting up, etc. Sounds like fuel to me.

BE CAREFUL. Running with no fuel in a cyl will do damage so don't do it long or continue to bet on it, etc.

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