1986 Johnson 150 V-6 Hard Start with Flooding

[Terrapin]

The subject engine has been running great and still runs fine after started. In addition, I am confident I know how to cold start this engine, and my procedure seems to mirror those described on this site. However, recently I noticed a change in the primer bulb when prepping the engine for cold start. This day the bulb didn't seem to get firm as quickly as it did historically. This seemed to contribute to hard starting and flooding. I thought the primer bulb needed replaced since it took so much priming to get the bulb firm with the bulb in the proper vertical orientation, so I replaced the primer bulb with an OMC/Bomabardier 3/8" primer bulb. However, this did not revert the priming process back to the historical condition. In addition, I am positive the primer solenoid lever is in the proper "clockwise to stop" position. It seems that the engine is flooding during the starting procedure. Pulling all of the plugs, drying them and letting the cylinders dry out eventually enabled me to start the engine and make the 10 mile run back home.

Can someone suggest a possible root cause of this problem and a method to verify the root cause? Thanks for reading.

 

[emdsapmgr]

Re: 1986 Johnson 150 V-6 Hard Start with Flooding

The primer bulb should pump up to "hard" each morning when your first cold start the engine. This event is caused by two things, the check ball valves in the primer bulb work correctly, and the floats in the carbs shut off incoming fuel when the bowls are full. You just replaced the primer ball and correctly oriented it during priming, so it is not the likely suspect. Possible something is going on inside the carb bowls with the needle and seats. Perhaps a float is bad, letting too much fuel into the carb(s). Have you removed the airbox cover to see what is going on when you prime the bulb first time each day? Any fuel running down the front of the carbs? Any excess fuel will get collected at the bottom of the airbox and get recirculated into the bottom cyl, overfueling it-perhaps to the extent the engine smokes a lot for the first minute or so of running and can simultaneously rough.

 

[Terrapin]

Re: 1986 Johnson 150 V-6 Hard Start with Flooding

Thanks for the reply. I will pull the airbox cover and see whether I see any excess fuel during the priming. Is there a way I can also check the primer solenoid for proper operation? Is there any chance it is bleeding fuel during the priming operation?

 

[emdsapmgr]

Re: 1986 Johnson 150 V-6 Hard Start with Flooding

Yes. You can pull that small hose off the hose barb on the very top carb. You should have fuel pulsing out the hose when you push in on the key switch (when the key is turned to on).

 

[Terrapin]

Re: 1986 Johnson 150 V-6 Hard Start with Flooding

Two days ago I pulled the air box cover to see if the priming operation would result in excessive fuel being dumped into the carburetor area. Surprisingly, the fuel system pressurized itself as it historically has; three or four pumps of the primer bulb pressurized the fuel system as usual. There was no fuel spilling from the carburetor.

I also pulled the primer hose off of the top carb and tested the primer solenoid operation by pushing the ignition switch. Fuel came out of the hose only when the ignition switch was pushed in.

Emdsapmgr, I believe you are thinking I may have a stuck float needle valve in one of the carburetors. The past two days the fuel system priming operation worked as it has historically. Do you have any other suggestions as to what else I can check out on the fuel system? Would you suggest that I rebuild the carburetors? Thanks for your help.

 

[emdsapmgr]

Re: 1986 Johnson 150 V-6 Hard Start with Flooding

You seem to be doing all the correct things regarding testing and analyzing things. All your efforts sound normal and appear to be yielding the correct results. Before you get into the carbs, you might have a look at the anti-siphon valve if you are running from a built in tank. Sometimes the ball valve inside can get minor debris in it which will affect the action of the ball and affect the flow through from the tank. I've seen sand (grit) actually stick the ball (partially open) in the valve. I believe you are doing this-but when priming the hose bulb, orient the bulb so that the arrow is pointing skyward-it will work better. Your red lever on the primer solenoid should run paralled to the length of the solenoid during normal operation.

 

[Terrapin]

Re: 1986 Johnson 150 V-6 Hard Start with Flooding

Thanks, I am following all of your suggested tips. Although everything is now working well, I have the anti siphon valve on my list of things to check out. I have an internal 63 gallon tank in my 1986 Boston Whaler Outrage 18. Someone told me the 1986 Outrages do not have an anti siphon valve, but I would like to check. Is the antisiphon valve typically inside the tank or on the exterior where the barbed gas line fitting is? I am also a bit worried about trying to open up the tank without shearing an access cover machine screw off. However, I want to get in there to make sure the screen is clean if in fact there is a screen on the gas uptake tube.

 

[metriccrescentwrench]

Re: 1986 Johnson 150 V-6 Hard Start with Flooding

Is the antisiphon valve typically inside the tank or on the exterior where the barbed gas line fitting is?

The anit-siphon valve IS the barbed fitting. If you're boat has one there will be a spring and ball inside the barbed fitting. They're not required when all parts of the fuel system are above the top of the tank (in other words a leak couldn't possibly result in fuel being siphoned from the tank into your boat).

 

[Terrapin]

Re: 1986 Johnson 150 V-6 Hard Start with Flooding

Metriccrescentwrench, Thanks for the heads up on the anti siphon valve being integral to th barbed fitting. I was in the marine store today and checked one out. Thanks again!