help!!!! 78' johnson 70hp

[new_2-boats]

engine starts perfect, runs fine low and high speed but when i stop, sit for a while it won't fire at all. Is it my carbs? time to rebuild or what? I despiritly need my boat this weekend!

 

[Goodoleboy]

Re: help!!!! 78' johnson 70hp

When you say it wont fire are you saying the motor just wont start. Or are you saying you have no fire to plugs.<br /><br />Give us a little detail on how you try to restart after its shut down for a while. Motor still warm or not. <br /><br />Good luck!

 

[new_2-boats]

Re: help!!!! 78' johnson 70hp

plugs have spark. It looks like it floods. Fuel comes out of the air intake. If I let it sit for a while( about 4 hours) with the plugs out. It will start right up. I don't have a clue?

 

[Goodoleboy]

Re: help!!!! 78' johnson 70hp

I would do a spark test on it. You can get a tester at auto. parts places.<br /><br />Spark must jump at least 7/16 gap. If it passes that test. Then I would suspect a bad needle and seat in one or more carbs.<br /><br />Try pumping primer bulb and see it it gets hard. If it dosent, then disconect from engine and trying pumping again if it still dosent then you have problem with check valve.<br /><br />If it does pump up hard the then problem is with carb floats, needle and seats. You will need to clean and rebuild.<br /><br />I would also supision that you may have one or more coils breaking down.<br /><br />Let engine warm up to full operating temp. while running at idel on muffs. 15 to 20 minuets.<br /><br />Then recheck with spark tester. See if all three past test again. If it dosent one or more then switch coils and see if problem follows coil.<br /><br />If it does pass then look into rebuilding and cleaning carbs.<br /><br />Do you have a manual?<br /><br />Good luck!

 

[Chinewalker]

Re: help!!!! 78' johnson 70hp

Outline your starting procedure for us. It could be as simple as you're choking it when you're not supposed to and flooding it out...<br /><br />- Scott

 

[papasage]

Re: help!!!! 78' johnson 70hp

when pumping bulb and dont git firm it could be the pump diafram . a hole in it will let fuel go into the block . sounds like needle valve seat isn1t seating . have bumped the carbs at times and they would seat but realy need a good cleaning

 

[new_2-boats]

Re: help!!!! 78' johnson 70hp

I tried a trick. If I pull the gas line off the engine and let it run out of gas it will start back up again. So, something isn't stopping the fuel from flowing when the engine is just turned off.

 

[new_2-boats]

Re: help!!!! 78' johnson 70hp

the fuel pump is brand new( 2 months)

 

[Goodoleboy]

Re: help!!!! 78' johnson 70hp

Carb needle and seats are bad. must be replaced. Mite as well clean carbs while you have them tore down. Blow all passages clear with comp. air.<br /><br />Good luck!

 

[Joe Reeves]

Re: help!!!! 78' johnson 70hp

Remove the carburetor face plate. Observe the carburetor throats while pumping the fuel primer bulb..... If fuel escapes, the carburetors need cleaning and rebuilding.<br /><br />NOTE.... When a engine has more than one carburetor, and one unplugs the fuel line to let the engine run out of fuel, the top carburetor runs dry of fuel (and OIL), leaving the engine to continue to run on the remaining carburetors.<br /><br />This results in having at least one aluminum piston run up and down the steel cylinder wall with improper or no lubrication. Not a good idea!

 

[Straightup]

Re: help!!!! 78' johnson 70hp

Great info Joe. I will keep that in mind when caring for my like new '84 Johnson 70.<br /><br />Jeff