1979 150hp johnson hp starts hard,poor idle

[danostults]

The engine won't start on boat ramp unless I pull it forward to point where water intake ports are still in water and then it fires up. It will start on the water after engine is warm. If it cools I raise trim to bring water ports near water surface and it will fire. A couple of times I had to squirt fuel in one of carbs. It idles poor, but accelerates fine and top end is fine. A compression test revealed a difference of 5 psi between 2 cylinders. Any ideas?

 

[billy4hp]

Re: 1979 150hp johnson hp starts hard,poor idle

Start here...

http://forums.iboats.com/showthread.php?t=225510

 

[tashasdaddy]

Re: 1979 150hp johnson hp starts hard,poor idle

what were all you compression readings? also setting idle on muffs does not work. there is not any backpressure on the exhaust. you have to set idle high, then fine tune it in the water.

 

[ezeke]

Re: 1979 150hp johnson hp starts hard,poor idle

You may find that increasing battery power will help. Make sure that the battery cables and connections are excellent.

By watching the action of the choke plates while cranking you can assure that the choke plates are closing 100% required for a cold start; do this with the air silencer off. If they are not fully closing, move the choke solenoid in small increments until they do.

 

[emdsapmgr]

Re: 1979 150hp johnson hp starts hard,poor idle

Poor idling can be caused by the idle being set too low. Should be 650-700 rpm in gear when sitting at normal rest in the water. If it still won't idle, you may have some dried fuel in the idle passages in the carbs. These passageways are different than midrange and high speed passages. That can be cured by ovehauling the carbs-make sure you completely disassemble and spray an aerosol carb cleaner through each passageway.