1974 85hp johnson carb problems

[jlmeritt]

im having problems with my lower carb on my boat. it keeps failing out both bottom plugs. ive taken off the bottom carb and cleaned it no change. the top carb runs great. its got good fire and great compression on both cylinders. i dont know what to do. it ran great last summer. can someone give me some ideas on what to do.....also i need a break down on how to put bearings in the prop and putting in an impeller. thanks

 

[Blade_Link]

Re: 1974 85hp johnson carb problems

im having problems with my lower carb on my boat. it keeps failing out both bottom plugs. ive taken off the bottom carb and cleaned it no change. the top carb runs great. its got good fire and great compression on both cylinders. i dont know what to do. it ran great last summer. can someone give me some ideas on what to do.....also i need a break down on how to put bearings in the prop and putting in an impeller. thanks

did you do a complete rebiuld? also id check your fuel mix on that carb
as fort eh prop bearing and impeller, for your impellor you need to disconnect your clutch dog (little hatch on the side of the leg) and drop the bottom end, the impeller should be on your shaft or enclosed in the bottom end, for your prop you need to take the prop shaft out, you may need to dissaseble the bottom end, you may want to replace your seals and gaskets at the same time

 

[tashasdaddy]

Re: 1974 85hp johnson carb problems

check your compression and spark. you need a manual for bearings.

 

[jjacobs007]

Re: 1974 85hp johnson carb problems

you need a 12 pack and a fresh pack of ciggs to fix the problem lol.

 

[emdsapmgr]

Re: 1974 85hp johnson carb problems

A couple of thoughts on the carb issue: Are both the carbs the same size throats? Do they both have identical jets in them? Are the bottom plug wires shorting out on the lower cowling latches? Are you running a thermostat in the engine? Check the cyl head temps with a laser gun to make sure they come up to hormal operating temps. Have you decarbed the engine lately? Do you know the if the float in the lower car bowl floats properly-the new ones are a composite material, some old cork floats get gas soaked and may not float properly. Check for strong spark on the bottom cyls when the boat is at planing speeds (under load.)

 

[ezeke]

Re: 1974 85hp johnson carb problems

To replace the impeller, you need to drop the gear case. There are a total of seven screws to remove from below including the one for the trim tab.

Then you need to release the shift rod which is connected midway under the carburetors. To release thje shift rod, loosen the screw that forms the fulcrum of the bellcrank and spread the fingers of the bellcrank so that the pin releases. Click the thumbnail.

Be sure to mark the position of the trim tab so that you can put it back as it was; you have to remove it to reach the screw that is hidden above it.

 

[jlmeritt]

Re: 1974 85hp johnson carb problems

A couple of thoughts on the carb issue: Are both the carbs the same size throats? Do they both have identical jets in them? Are the bottom plug wires shorting out on the lower cowling latches? Are you running a thermostat in the engine? Check the cyl head temps with a laser gun to make sure they come up to hormal operating temps. Have you decarbed the engine lately? Do you know the if the float in the lower car bowl floats properly-the new ones are a composite material, some old cork floats get gas soaked and may not float properly. Check for strong spark on the bottom cyls when the boat is at planing speeds (under load.)

both carbs are the same size. i was thinking about switching them around to see if that changes anything. the temp is all the same on all four heads. what is "decarbing the engine" and how do i do this. the float is composite and no gas in the float and its working fine also the needles in great shape. when i run the motor at half throttle it trys to run good. if i slap it wide open it does great.

 

[jlmeritt]

Re: 1974 85hp johnson carb problems

check your compression and spark. you need a manual for bearings.

ive got great compression #3 is 95 #4 is 97. while its running i pulled a plug wire and you can here it arking in the boot and # 4 plug wire bit the **** out of me. but theres no change in the motor like those too cylinders are dead. i can spray a little carb cleaner in bottom carb and it tries to run better.

 

[jlmeritt]

Re: 1974 85hp johnson carb problems

did you do a complete rebiuld? also id check your fuel mix on that carb
as fort eh prop bearing and impeller, for your impellor you need to disconnect your clutch dog (little hatch on the side of the leg) and drop the bottom end, the impeller should be on your shaft or enclosed in the bottom end, for your prop you need to take the prop shaft out, you may need to dissaseble the bottom end, you may want to replace your seals and gaskets at the same time

can you tell me how to check the fuel mix

 

[Daviet]

Re: 1974 85hp johnson carb problems

You should not spray carb cleaner in a running engine, it does not have any oil in it, no lube to piston. Use a squirt bottle with proper oil/gas mix and squirt into lower carb. If the RPM picks up and engine tries to run, you know you have a fuel problem.

 

[emdsapmgr]

Re: 1974 85hp johnson carb problems

You have not mentioned whether you recently completed a carb overhaul. If the engine was not properly winterized last year, you could have any dried fuel in the carb passages. When this happens, they won't flow fuel. An overhaul will involve complete disassembly, removal/visual inspection of the jets and thorough cleaning of all the passages with an aerosol carb cleaner.