14' boat wont plane out with 50hp johnson

[Jrich311]

I have a 71 50hp johnson model#50ESL71S that starts and runs great out of the water but once you get it in the water it wont go faster then headway speed. I noticed that the plug in the bottom cylnder wasnt getting as hot as the top and the plug was staying wet with gas and the top was dry. I was told I may have a bad coil so I switched the bottom coil to the top and the problem didn't switch cylnders. Next I put new NGK plugs in now it seems that both plugs are getting hot but the top plug was darker and came out dry while the bottom one looked almost new and came out wet. I was told that if it wasn't the coil I probably have a bad switch box. Does anyone have any ideas or agree with the swith box idea. I want to make sure before I go blow more money on another part that might not fix it. I would bring it some place but it's hard to find a place that will work on a motor this old. Thanx for reading and look forward to any help.

 

[JB]

Re: 14' boat wont plane out with 50hp johnson

Howdy, Jrich.<br /><br />Time to do some troubleshooting. Replacing parts is not troubleshooting, it is wasting bux.<br /><br />Your problem has been addressed at least 300 times in this forum. All of the questions, answers and advice are on www.outboardrepairs.com.<br /><br />Go there and look up power loss. Be prepared to stay a while.<br /><br />Let us know what you end up doing and the results you got.<br /><br />Good luck.

 

[Jrich311]

Re: 14' boat wont plane out with 50hp johnson

I went to the power loss section but didn't find anything that really matched up with my problem. I did however come up with some other questions...<br />1st I know that the motor will run on each cylnder individualy without the other hooked up so my question is could the bottom cylnder not be getting enough spark to burn all the fuel, and if so would a switch box have anything to do with this.<br />2nd is there a test i could do to figure out if it's a fuel or electrical problem?<br />I forgot to add that the buzzer in the control box goes off now and again but it's not an all the time thing could this have something to do with the problem?

 

[JB]

Re: 14' boat wont plane out with 50hp johnson

Howdy, Jrich.<br /><br />You are almost certainly running on one cylinder.<br /><br />Pump your primer bulb when this happens. If it picks up power, you have a fuel supply problem.<br /><br />Squirt some premix into each carb. If it picks up you have a problem with that carb.<br /><br />Remove each spark plug and attach the plug wire. Hold it against the block and see if there is a hot, blue spark when you turn it over. <br /><br />Finally, short out each spark plug at idle. If there is no drop in rpm that cylinder is the one not making power. If it dies, that is the cylinder that is okay..<br /><br />Let us know what you find.

 

[Jrich311]

Re: 14' boat wont plane out with 50hp johnson

Thank you for all the tests, I will try them all today. I do no that if you diconnect the top cylinder it will stall, but if you pull of the bottom plug wire it will keep running. You also get a nice shock hahaha <br />One other thing someone told me I should pull of the flywheel and file the points does this sound like something that would work on a 71 motor? Thanx again

 

[ledgefinder]

Re: 14' boat wont plane out with 50hp johnson

That's an overheat alarm you're hearing. I wouldn't run it until you get it figured out, could easily ruin the motor. <br /><br />Most likely cause would be that the water pump is shot, probably needs a new impeller.

 

[ssulkazi]

Re: 14' boat wont plane out with 50hp johnson

no spark sounds like , or no air

 

[Jrich311]

Re: 14' boat wont plane out with 50hp johnson

I pulled the plugs today and did the spark test it looks like both are getting good spark.<br />I tried pumping the primer ball and it did nothing.<br />I took the cover of the air box and sprayed pre mix in each carb, when I sprayed it in the top it almost died out and when I sprayed it in the bottom the RPMs shot up.... Does this mean the bottom carb isn't getting enough fuel?<br /><br />As far as the buzzer in the control box goes it comes on as soon as you start the engine sometimes and sometimes it dosen't come on at all... Could this be a short someplace? The lower unit seems to spit water fine...<br /><br />I look forward to any advice thanks

 

[jim dozier]

Re: 14' boat wont plane out with 50hp johnson

You've narrowed the problem to insufficient fuel in the bottom cylinder. Most likely a gummy carb in need of a rebuild. Remove the carbs (do bothe while you're at it) and completely disassemble them with particular attention to the main jets and float valve, soak them overnite in carb cleaner, blow out with compressed air, install a carb rebuild kit and set the float adjustment and idle mixture adjustment.<br /><br />Also check fuel hoses for air leaks at carb fitting.

 

[Jrich311]

Re: 14' boat wont plane out with 50hp johnson

Thank you for all the help everyone I'll go pull the carbs out today...<br />I have herd it's pretty hard to adjust the twin carbs is this true and if so does anyone have any tips?<br />My only real experience with carbs is on vehicles<br /><br />Now if I can just figure out the buzzer I'll be all set for the water

 

[jim dozier]

Re: 14' boat wont plane out with 50hp johnson

Several people have written how to do it on this forum. Do a search. There are only 2 adjustments on the carb, float level and idle mixture. You need a manual for the float but usually it should be level with the bottom of the carb when the carb is upside down. For the idle mixture, open the idle mixture screw 1 1/2 turns (unless the book says different) and warm it up in the water (not on muffs). Set idle speed to 700 rpm (unless the book says different). Open 1 carb at a time 1/8 of a turn until optimum engine speed then open 1/4 turn more. Reset idle speed to 700 rpm. Then do the other carb. You might have to go a second round on both carbs to get the best balance. Each engine has a link and synchronization sequence to link and synchronize the ignition timing wiht the throttle control that is different than others, and that is why you need a manual.

 

[ledgefinder]

Re: 14' boat wont plane out with 50hp johnson

The alarm does sound like it might be a short. <br /><br />When the engine is warmed up, the cylinders should be about 140 degrees F - hot enough that you can rest your fingers on them for 2 to 5 seconds. <br /><br />Not sure where the heat sensor is on the 50hps, probably somewhere on the cylinder head.

 

[Jrich311]

Re: 14' boat wont plane out with 50hp johnson

I just finished doing the carbs, and there was crud in the bowl...<br />Now when I spray pre mix in the carbs they both almost die out<br />I ran it for a while and pulled the plugs I was able to handle both with out getting 3rd degree burns and both came out moist..<br />What should the plugs look like?<br />When I took out the main needle I just counted how many turns I turned it out and put it back in the same number. I kept the float needle adjustment where it was. <br />I also noticed the alarm didn't sound could the top cylinder have been running to hot due to the bottom cylinder not running right? Before I did the carbs I couldn't touch the top plug when I took it out...

 

[Solittle]

Re: 14' boat wont plane out with 50hp johnson

rich - Please get a shop manual for your motor. OMC is the best and get the parts catalog while you are at it.

 

[Jrich311]

Re: 14' boat wont plane out with 50hp johnson

Thanks everyone I put the boat in the water today and it went great, the over heat alarm stopped as well.<br />This site has been very helpful...