Damn Boat Motors

Duckslayer100

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Ok, backstory: Bought a used Johnson 50 from a feller in Minnesota. Great guy. Honest. Helped me install it and hook everything up. Ran great.

Brought it home and the trouble started. Changed fuel line. Replaced spark plugs. It runs a bit better, but not much.

Weird thing is I can get it to run fine idle great in the driveway. Then I go to the lake, and it bogs down after starting, starts hard, and won't idle even after running it for awhile.

Yesterday was the first time ever that I was able to idle the motor after running it across the lake. But it only did it once.

Got it back home. Hooked up the garden hose and started it. Ran just fine and idled like a dream.

WTF is going on?? Why does it run fine in my driveway and not on the water? I realize there's a joke in there somewhere, but seriously...
 


Colonel Angus

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sounds like sticky float or needle valves...I'd run some sea foam through it to see if it cleans it up. If you are wondering why/how....the angle of the engine is probably different in the driveway vs on the water.
 

2400

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I would either check the coil or just replace it. Years ago I had a Chevelle that would idle and run just fine until I put a load on it then it would sputter and die. Changed the coil and it ran perfectly.
 


martinslanding

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cracked head? while the hood's off and it's idling is there any fluid (gas) leaking or squirting out of the block or head area?

this is exactly what mine did before she blew the "titty sprinkles" up
 

DerHornen

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You might need to readjust your throttle linkage to get idle RPM up a little. I had a '96 Johnson 115, carbed with VRO oil injection, that would always idle a higher in the driveway than on the water, maybe 200RPM. I got a hold of an original service manual and reset the throttle linkages per the instructions and it idled better afterward.
I think the back pressure on the exhaust when in the water versus when it's on a garden hose has just as much effect as the motor angle.
 

Duckslayer100

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You might need to readjust your throttle linkage to get idle RPM up a little. I had a '96 Johnson 115, carbed with VRO oil injection, that would always idle a higher in the driveway than on the water, maybe 200RPM. I got a hold of an original service manual and reset the throttle linkages per the instructions and it idled better afterward.
I think the back pressure on the exhaust when in the water versus when it's on a garden hose has just as much effect as the motor angle.

Hmm..that could be it. I had to put the control cables into a next control box and just popped everything into place. It idles at 2,000 RPM in my driveway. I wonder if it may be calibrated wrong.

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I should note that it runs great at speed. Absolutely no hesitation. It just won't idle. Bogs down and dies. I have to watch the RPS and pop it into gear, then she's just fine. I know this is bad for the transfer case, however, which is why I'd like to get the idle business figured out.
 

jdinny

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You might need to readjust your throttle linkage to get idle RPM up a little. I had a '96 Johnson 115, carbed with VRO oil injection, that would always idle a higher in the driveway than on the water, maybe 200RPM. I got a hold of an original service manual and reset the throttle linkages per the instructions and it idled better afterward.
I think the back pressure on the exhaust when in the water versus when it's on a garden hose has just as much effect as the motor angle.

mine ran similar 2 years ago and it in fact was a throttle linkage. $8.00 part

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on a 90hp merc, 1990

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it wouldnt cut out and die though just ran rough. i had a brother in law look at it who is an outboard mechanic and did a compression text and all that shit and figured it out while sitting and running it in my driveway. he aslo said he played around with one of the carbs due to some minor backfiring. it has ran flawlessly every since.
 

eyexer

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you have a clogged idle circuit in the carb(s). Pull it/them off and tear them down completely. remove all jets. soak carb in a gallon can of carb cleaner. then remove and spray out with carb cleaner then air. Install new bowl gasket when you put them back together. If you want you can run seafoam in it for a few tanks. Might come out of it. But chances are it won't.
 


Duckslayer100

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you have a clogged idle circuit in the carb(s). Pull it/them off and tear them down completely. remove all jets. soak carb in a gallon can of carb cleaner. then remove and spray out with carb cleaner then air. Install new bowl gasket when you put them back together. If you want you can run seafoam in it for a few tanks. Might come out of it. But chances are it won't.

I think the motor only has one carb, so that might be a good first step. I'll see if I can get a new gasket ordered.
 

espringers

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I also think it's a carb issue. Could just be a sticky float. Mine did the exact same thing. It would idle fine at home cause it had a dry bowl. But, after running for a bit on the water, the float would stick and it would be perpetually flooded. Could literally see gas in the water.
 

Duckslayer100

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I lied. The motor has two carbs. But I looked at the service manual last night and it doesn't look too difficult to take them off. It suggests buying carb kits ahead of time because all the gadgets need to be replaced. It also said there are some screws that can't be reused after they're removed. I've never heard that before. Is that legit?

The carb kits I've seen come with a lot of parts, but I don't think screws. Plus it suggests getting hoses in case the fuel lines need to be cut off. Hopefully that isn't the case. Can you buy those small fuel hoses just about anywhere, or would that be a special order part, too?
 

eyexer

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napa will have the fuel lines. most of those kits are generic to numerous different models so all the parts are always used. It would be a good idea to get the kits. Get on ebay and you'll get oem kits for probably half price.
 


espringers

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Buy the kit and use every new part possible. And if your gas is from last year, bite the bullet and dump it.
 

Duckslayer100

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napa will have the fuel lines. most of those kits are generic to numerous different models so all the parts are always used. It would be a good idea to get the kits. Get on ebay and you'll get oem kits for probably half price.

I bought two off Amazon. Had a $50 gift card from my birthday, plus free shipping. Came out ahead.

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Buy the kit and use every new part possible. And if your gas is from last year, bite the bullet and dump it.

Brand new gas once I got the motor installed. Old gas had been sitting in there for at least a decade. Pumped it out best I could and added fresh stuff.

And I got two kits coming. Hopefully that does it. Just need to pick up a bunch of carb cleaner now.
 

hogslayer

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Does it seem like it is not idling because it is not getting enough fuel or because it is flooding out. After it dies how hard is it to start again? Do you have to open the fast idle all the way up to start it? I'm guessing it is most likely the idle circuits in your carbs. They are very small orifices and mixed gas will very quickly varnish up and clog or restrict them if the motor has sat for even a couple months some times. With the muffs on in your driveway you don't have any backpressure and air can flow very easily through the engine. The more air flowing through your carb the more fuel getting sucked out the idle passage into the intake through venturi effect giving you enough to idle good. Less air flow through the engine while in the water due to backpressure and you do not have quite enough fuel getting sucked in at idle. You probably don't need a kit and can get by with just cleaning them. As stated you can soak it in carb cleaner, stanasol or even diesel fuel works very well. Take a can of aerosol carb cleaner with the red spout thing and blast it through the passages and then blow them out with compressed air and you should be good to go. Sometimes the carb needs to be adjusted throughout the season on some motors. I had a motor that would idle beautifully in the spring in the cold dense air but would flood out really bad at idle during the summer when it was hot. I had to adjust it to give it more fuel in the spring and turn it back down in the summer. Carb issues can be a pain, but usually pretty easy to remedy. Good luck
 

Duckslayer100

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Thanks Hog. You mirror what others are saying.

I'm sure I could get by without a carb kit, but figured might as well just do it all as long as I have the sucker off the motor.
 

Allen

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And for heaven's sake, wear safety glasses of some sort when cleaning a carb with spray cleaner. You never know where the ports are connected and you will most certainly get spray back in your face.

Trust me, I know. I just did a carb for a weedwhacker a few weeks ago and took a few good shots of carb cleaner to the face.
 


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