1972 65HP Johnson starting / idling issues

[awakeatground0]

I have yet to not get my 72 65hp johnson started but most of the time it is stubborn. When i choke the motor it will not start at all and just floods the carbs to the point where they are dripping fuel from each intake. To get it started i have to leave it un-choked with the throttle plates about half open(when it starts, rpms are around 3000). When motor is started, i drive it for a while to warm it up, then i begin to lower the rpms and start to try and tune each carb starting with the center carb. I can get the rpms(under load) down to about 1200 before the motor wants to stall. When the motor does stall, i have trouble getting it started. I have to back out the needles on each carb and once again un-choked start the motor at half throttle(give or take). When i pull the plugs they are fouled badly. One time i had to pull the plugs and clean them just to get back to the dock.

Things to know: I have pulled each carb and cleaned them( removed some gunk from idle jets and some oil deposits from main jets)

The motor will bog down at WOT from time to time, in this case, i put in neutral and rev a few times, and then off she goes with no bogging.

I switched spark plugs from the kind that you gap to the kind that are gapless(I believe this is the reason for fouling at low rpms however i still had issues with the motor bogging at WOT with both plugs)

I am running 87 octane with 50:1 mix and starbrite star tron enzyme fuel treatment.

After running motor at WOT for 15 - 20 minutes, motor is lupe warm to the touch, definately not overheating, but seems to be a little cool for those kinds of operating conditions maybe? I can put my hand anywhere on the motor and leave it there without flinching.

I think that is all, any advice would be greatly appreciated. Thanks

 

[eclark53520]

Re: 1972 65HP Johnson starting / idling issues

Sounds like your carbs are messed up. You're running WAY too rich, which is why you can't get the RPM's down, too much fuel in the air/fuel ratio means no ignition.

Are the floats adjusted correctly? Are the corrects jets installed/Adjusted(depending on type of jet) correctly?

This is almost assuredly a carb problem.

 

[Scurvy Knave]

Re: 1972 65HP Johnson starting / idling issues

If the motor is difficult to idle before you run it awhile, you might have a faulty T-stat that is stuck open. That would explain poor idling, fouled plugs, and cool head.

It sounds like you're getting way too much fuel - but you're timing might be a bit off as well. Make sure that the throttle linkage to the throttle valves is set correctly - they should be fully horizontal at WOT and just begin to open when you come off idle. Check the spark timing.

I'm assuming that when you cleaned up the carbs you ensured that the floats were set properly and that the needles valves operate correctly. How did the floats look. Some guys on here report old floats getting gas-logged and not floating properly.

 

[Scurvy Knave]

Re: 1972 65HP Johnson starting / idling issues

Oh, and btw, welcome to IBoats!

 

[awakeatground0]

Re: 1972 65HP Johnson starting / idling issues

i was wondering if the thermostat was stuck myself. as for the floats in the carbs, they are in good shape and so are the needle valves that operate with the floats, there is no gas in the floats(i shook them by my ear, and put them in water to make sure they were floating correctly) and it looks like the carbs have been rebuilt recently before i purchased the boat with motor. Now, as for adjusting the floats i am confused as to how i should do this, i read in a sticky that the carb should be upside down with the float horizontal. So my question is, how do you adjust the float?, do you bend the hinge until the float is horizontal while the valve needle is bottomed out(closed)? Also, I was curious if i should be running different spark plugs, instead of the gapless plugs that i have in there. Seemed that it ran a little better with the plugs that have the prong you can gap. Thanks for the welcome to I-boats and for the advice guys!

 

[awakeatground0]

Re: 1972 65HP Johnson starting / idling issues

ok, so after some research, i found that the carb floats should be adjusted with the carb upside down and the valve needle should contact(close) with the float ever so slightly higher(just above horizontal) on the opposite side of the floats hinge where the valve needle is. Is this the correct adjustment? also, if anyone knows the exact height(inches, mm, etc.) adjustment for these floats that would be awesome. I tried looking it up and couldnt find anything. thanks for all the help!