# 58 18hp johnson hard to start and no rpm at WOT



## riverbronzeback (Sep 22, 2008)

I have an 18hp 1958 johnson. I cleaned and rebuilt the carb. After i reasembled i couldnt get it to start. Shot some starting fluid in and it fired right up. Runs smooth and idles very well. Will start when it is warm but if i wait too long wont start back up. After cranking plugs are wet. So can i assume it is getting enough gas. Maybe weak spark. I know the points need cleaned or replaced probobly. Like i said before idles real good but at WOT it seems like im getting only half throttle. Also my motor has the silencer on the carb, does it matter if it still off. When i look into the carb while running it seems like a lot of gas spraying inside. Oh almost forgot, last time i tried cranking it over i had gas coming out of the choke opening. I guess more than one problem? Im new to working with outboards so please help. Also ran seafoam in the tank today.


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## Loggerhead Mike (Sep 22, 2008)

take your plug out and ground it to the head. is the spark nice'n blue? my motor did a simular thing. it would start and idle, but in gear under load at wot it wouldnt build any rpms. turned out i had a vacuum leak from not replacing the carb gasket after rebuilding the carb. id clean the plug, try and get it to start and run it for awile, so you can look at the plug and see if its runing rich or lean


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## riverbronzeback (Sep 22, 2008)

Should the spark be very visible or does it have to be pretty dark? Update. When i got home from the lake i pulled the plugs and top one was wet with gas. Bottom one was dry. So can i assume top cylinder not firing? Do you think i have such a weak spark that it takes starting fluid to get it to ignite. I pulled the flywheel to inspect the points. What am i looking for here? Like i said before outboards are new to me and any help would be appreciated. Does any of this make sense?HELP


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## riverbronzeback (Sep 23, 2008)

Heres what i figured out so far. I found out i have no spark on the bottom cylinder. Cleaned and set the points. Still no spark. Does this sound like a coil?


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## ben2go (Sep 23, 2008)

riverbronzeback said:


> Heres what i figured out so far. I found out i have no spark on the bottom cylinder. Cleaned and set the points. Still no spark. Does this sound like a coil?



Yes or a bad plug.Switch the spark plugs and try again.If you have no spark,I would replace the condenser(round silver cylinder with 1 wire) and the coil.


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## Riverjet502 (Sep 23, 2008)

I would look real close at the coils and see if they have any cracking or leakage coming from them. Those old coils were known to be notorious for cracking. If it was me and I planned on using this motor a lot. I would replace the entire ignition. Coils, points, condensor, plug wires, plugs, I would hate to get out on the water only to have a nice long paddle back to the ramp because I was to cheap to do it right. These are good o'l motors and will run and run. What kind of shape is your old pressure tank and hose in? Parts are still available to rebuild these as well.


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## Loggerhead Mike (Sep 23, 2008)

if you have access to a test light (there inexpesive at the auto store) hook it to the end of the coil and have somebody turn the motor. even better, if you have a friend with a multi meter you could test the resistance in the condensor-coils-wires-caps. the spark should be nice and blue and visable in daylight, any other color indicates a week spark. you can also try turning it over at night, and you'll see if you have a spark jumping from the wire to head or ect. electricity will travel the least resistant path. are your plugs gap'd correctly?


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## riverbronzeback (Sep 23, 2008)

Switched plugs same result. Kind of short on money so only replace what i can to make run. When money permits will replace all parts. In the mean time i have a 6hp johnson 1975 that has all the same part numbers for ingition systems that i can swap parts from. I have a multimeter so i can check coils. What is the procedure for checking these. Is is just checking resistance on the coil. My pressure tank is good shape but i am considering converting to fuel pump for safety reasons and so this motor will run off the same tanks as my other motors. 1966 johnson 9.5 i am running on my decked 1440 smokercraft jon. It just does not have enough for the boat after decking. This is why i bought this 18hp. Also have 1975 johnson 6hp that was my grandfathers. 9.5 will get sold once i know the 18hp is reliable. I fish St. Joe river in southwest michigan and 9.5 way too slow for a 8-10 mile run down river and back. I will try to swap coils from 6hp to my 18hp tonight and see if motor will fire. With just one cylinder firing this would make it hard to start? And the only way i could see a spark was to turn lights off at night. Is this too weak? Thanks guys for responses. Love this website, cant get enough. Will post pictures of motor and boat when i figure out the picture thing.


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## Loggerhead Mike (Sep 23, 2008)

deff. to weak. unplug the coil and take the plug wire off at the coil. hook the dmm up on each side and check for infanint resistance, depending on the dmm, it should say O.L or just show 0. you cant have any of these plug'd up to check um. the dmm shoots a voltage threw it to measure the resistance


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## riverbronzeback (Sep 24, 2008)

I HAVE SPARK!!!!!! I put the condensers from other motor on and still had no spark on top cylinder. Then i switched coils from one cylinder to the other and still same result. Then i flipped condensers from one cylinder to the other and at the same time took another look at the points on that cylinder. Readjusted the gap and cleaned points. Put back together and have real good spark that i can actually see with lights on in garage. Was 1am when i fineshed so i have to wait till after work to try so start. So coils were good all along and really dont look very old. I know condensers were good cause came off running motor. So this means problem was in the points all along. Think it will start now? Again, thanks for the help.








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## Loggerhead Mike (Sep 24, 2008)

haha, you gotta love workin on stuff untill the wee morning, then gettin up to go to work. let us know how it runs


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## riverbronzeback (Sep 24, 2008)

Though it would start today. Went out this morning and first pull it fired for a couple seconds. Second pull same thing. After the first pull i could get nothing. I cant even get it start with a spray in the carb. Check spark, still have spark. Started thinking how i should have done a compression tester. Off to store. Came back with tester and spark tester and also brand new plugs. Checked compression both read 70 on the dot. This is low isnt it? My 9.5hp johnson reads 60 on both cylinders. I was reading a post and the guy was talking about one way he was getting 60-70 and the other way he was getting over 100. My 9.5hp runs and starts great and is used 2-3 times a week for the last 5 years. So i have spark that tests well with testing light. Compression is equal on both cylinders(maybe too low?) Now am i looking back at fuel system. Maybe i got the carb wrong on rebuild. Seemed to be very simple when i did it. If the compression is too weak will i not get enough pressure for my two line old fuel tank. I was told if the tank is in question put it above the motor and it will gravity feed. This didnt help either. Im gettting very irritated and my wife is even more fed up with me. I cant stop till i figure it out. Thanks for the advice. SMALLMOUTH RULE!


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## riverbronzeback (Sep 24, 2008)

Just went back out to garage. Hooked up spark plug tester to top cyl. Bottom cylinder plug was grounded to motor. Barely pulled rope and top cyl fired. Put bottom plug in and tried to crank and nothing. So this has happened twice. It did this this morning and this evening again. So after it sits for a while it will fire once and not again. Carb not right so too much gas? Another day or two of this and it will make a very heavy anchor for those windy days.HAHA


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## Captain Ahab (Sep 24, 2008)

I feel your pain - you are so damn close to getting it.

take another look at the carb - is the float possibly stuck dumping too much gas?


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## riverbronzeback (Sep 24, 2008)

Thanks Capt Ahab. Float is sticking. Realized when i ordered carb kit i got the one without float. Unstuck float put back together. Fires right up. First Pull. Lots of smoke though. Running too rich? Will river test tomorrow after work. Thanks everybody for all the help. I have learned so much in the last few days. Next thing is impeller. Not too difficult right?


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## Loggerhead Mike (Sep 25, 2008)

what color smoke? mine usually smokes at startup untill it gets warmed up


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## Captain Ahab (Sep 25, 2008)

riverbronzeback said:


> Thanks Capt Ahab. Float is sticking. Realized when i ordered carb kit i got the one without float. Unstuck float put back together. Fires right up. First Pull. Lots of smoke though. Running too rich? Will river test tomorrow after work. Thanks everybody for all the help. I have learned so much in the last few days. Next thing is impeller. Not too difficult right?



Glad it works out - do not worry about the smoke - that is probably from all the fuel getting dumped


Adjust the air/fuel mix once you get the engine hot (after like a 1/2 hrs cruise) and you will be fine.

The impeller should be easy


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## riverbronzeback (Sep 26, 2008)

Well today was the day i was taking her out on the river. But on my way to work truck broke down. Something in the rear end. Had to have it towed to the house. Wife wont let me put a hitch on our Pacifica. Says it is not for towing. Bummer. Maybe borrow dads Blazer tomorrow. I will try tomorrow. I cant wait to get it out and see how shell do. I know impeller is important but it pumps water stronger than any of my other motors. Should be ok for now. It will be nice to be able to get down river and find some new spots. How fast do you guys think it will go. 1440 Smokecraft jon decked front and back with floor. Im guessing i added a couple hundred pounds with mods. 2x3s and 1/2 inch ply. One battery and trolling motor and i usually dont keep much with me.


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## riverbronzeback (Sep 26, 2008)

Oh, forgot to say picked up new float and pin. The pin from my motor was plastic and to thick. Float would not move free enough. My dad said he had never seen a plastic one. Installed the new metal one and new float then adjusted. Now starts right up. Most of the time it pops right off without even choke. Cant wait to try it out. CRAPPY TRUCK!!!!!!!!


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## Loggerhead Mike (Sep 29, 2008)

did you find out whats up with your truck?

i'd venture to say your going to fly down the river with that motor =D>


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## riverbronzeback (Sep 29, 2008)

Sounds like it is either the pinion seal and bearing on the rear end. Or i have more major problems in the rear end itself. Got it half way torn apart Sunday. Will try to finish monday night. Supposed to rain tonight so maybe not. Trying to get my buddy to tow my boat to river if truck not finished soon. I hope river test goes well cause i listed my 9.5 for sale on ebay last night. That was deal with the wife. I do think i have her talked into letting me keep recently purchased 57'johnson 3hp. Such a cool little motor and runs great after replacing cracked and busted up coils. Still need to rebuild carb on it but still runs really good. SMALLMOUTH RULE!


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## Loggerhead Mike (Sep 29, 2008)

ouch. what kinda truck you drivin? we got all the software @ the dealership if you need some help gimmy a holler and i can send you some info ( preloading specs ect ect)


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