73 115 johnson hard to cold start

[Bartman]

First post long time reader. I have a 1973 115h/p Johnson. It's very hard to start when it's cold. If I put 10 drops of fuel into each cylinder thru the spark plug hole it fires up and runs GREAT. I can shut it off and it fires back up with no problem. Here's what I've done so far. Compression is 115 on all cylinders checking while motor is cold. Brand new power pack,2 new coils, 4 new sparkplugs. Cleaned carbs completely and rebuilt. Biggest new marine battery that wal-mart has. New fuel line with pump bulb from tank to fuel pump. Choke solenoid works fine. I did have to adjust the choke butterflies. One was 1/4 open while the other was shut. Any info or suggestion is greatly appreciated. This things runs like a new motor after it starts the first time

Thanks
Bartman

 

[bowrider]

Re: 73 115 johnson hard to cold start

Hi,
I had the same problem when I first got my boat about 2 months ago, same engine but a 74. I also put new sparks, 1 new coil, but I haven't rebuild the carbs yet. I ran a can of seafoam, and did a decarb. That thing starts right up now.
There some instructions for the decarb process in the FAQ's.

 

[ezeke]

Re: 73 115 johnson hard to cold start

I would have to say that you will find that the chokes are still not 100% fully closed when you are cold starting. There are a number of reasons, but just get in there, look down the throats and watch while someone else hits the toggle switch.

Here is why: The choke plates cut off the air supply so that the suction created by the movement of the pistons is focused on pulling the needed extra fuel from the float bowls.

You can simulate this effect by blocking the carb throats or manually introducing fuel, but in the end you need to get setup so that the system works properly.

One slightly less likely possibility is that the capillaries leading to the floor of the carburetor throats from the low speed orifices are clogged - they are the source of the gasoline for starting.

The brass screws on the lower outsides of the carb barrels lead directly to those orifices and the capillaries above them. You can try to clean them with compressed air and a little Gumout. If you open both the choke and throttle plates, you can observe the capillaries and see fluid sprayed from the open orifice.

The reason that you only have a problem when the engine is cold has to do with the volatility of cold gasoline and the fact that the gasoline that was there has evaporated.

 

[tashasdaddy]

Re: 73 115 johnson hard to cold start

agree with exeke, also is one of the greatest things you can do for your engine, rather than buying Seafoam Deep Creep, use the regular, in a spray bottle, and spray into the carbs, until it almost stalls. it's going to smoke like it's going to blow up. get the old crud out.

http://forums.iboats.com/bbBoard.cgi?a=viewthread;fid=36;gtid=1035563

 

[Bartman]

Re: 73 115 johnson hard to cold start

ezeke is da man!

Upon further inspection, the choke flaps were closed until I started cranking the motor. When the motor was being turned over, the choke plates were flapping do to the vacuum being pulled thru the carbs. I tighten the spring from the choke selinoid to the choke plates and it fired right up. Something so simple that I would of never figured out.

The batteries are being charged and we are heading out @ 5:00 am. THANKS A MILLION

Bartman