78 200hp johnson starting problem

[kirk750]

I hope someone can give me some advice. I pump primer until it is hard and then give it three more hard pumps it will start after alot of cranking. primer and fuel lines are new carbs are clean. once it starts it runs perfect and will start right up however if it sits for three or so hours it is hard to start. I know my fuel is draining back but don't know why. Any ideas would be appriciated thanks.

 

[emdsapmgr]

Re: 78 200hp johnson starting problem

Does the boat have a built-in tank, or do you use the loose, 6 gallon type? If it is a built-in, look for the problem in the fuel anit-siphon valve, mounted in the top of the tank. May have dirt, debris in it-causing it to malfunction. This is a common problem with these valves. Any dirt/debris can also impede fuel flow at high rpm.

 

[kirk750]

Re: 78 200hp johnson starting problem

The boat does have a built in tank I will check out the antisiphon valve but would that make the primer so hard to pump?

 

[emdsapmgr]

Re: 78 200hp johnson starting problem

The primer bulb could be defective. Have seen many of them where the valve balls will malfunction, restricting fuel flow. OMC color coded their newer/replacement bulbs with yellow plastic ends (as opposed to the black ends.) Try another fuel hose.

 

[ondarvr]

Re: 78 200hp johnson starting problem

I didn't see any mention of the the choke or primer (different than fuel line bulb) being used in your method of starting it. I have a 76 200hp and it starts fairly easy. <br /><br />Why do you think the fuel is draining back?

 

[kirk750]

Re: 78 200hp johnson starting problem

Checked anti-siphon valve and was leaking by will try and let you know thanks for the help.

 

[kirk750]

Re: 78 200hp johnson starting problem

Changed antisiphon valve and is still hard to start wondering if anyone has anymore ideas? thanks

 

[ondarvr]

Re: 78 200hp johnson starting problem

You said you pumped the bulb, but you didn't say anything else about your starting method. Do you use the choke (primer) and does the choke work? Have you tried spraying some premix into the carb to see if it starts cold? If it starts easy with the premix then you know where to start looking. Check the compression, low compression can cause poor starting. Check for good spark, crisp and blue, not weak and yellow.

 

[kirk750]

Re: 78 200hp johnson starting problem

When I start the motor I use the choke but it only chokes on two carbs and that is how it came from factory. The motor has 105psi on all cylinders and has good spark. Ondarvr what method do you use to start ypur motor?

 

[ondarvr]

Re: 78 200hp johnson starting problem

for a cold start I pump the bulb a few times, advance the throttle just a little, hit the choke and then crank. After 3 to 5 seconds it will fire, it may not stay running the first time if I don't work the choke correctly (on and off a couple of times), but the second time it will fire sooner and normally stay running. Unless it's very cold out I don't need to use the choke the rest of the day, I just turn the key and it starts instantly.<br /><br /> I did put new coils on it, rebuilt the carbs and did a link & sync.

 

[ondarvr]

Re: 78 200hp johnson starting problem

 

[kirk750]

Re: 78 200hp johnson starting problem

It seems like the carbs are not filling with fuel when I prime it but the bulb gets rock hard.I have pulled the fuel filters (sreens on pumps)apart and they seem to be fine.

 

[ondarvr]

Re: 78 200hp johnson starting problem

What is it that makes you think fuel is not filling the carbs when the motor is cold? There should be a drain plug (screw) on the side of the float bowl, take it out and pump the bulb, fuel should pour out. When it's cold try spraying pre mix into the carbs before you start it, if it starts easily then you know it's a fuel issue, If it's still difficult to start you need to look at other things.

 

[kirk750]

Re: 78 200hp johnson starting problem

I have pulled the bowl drains and fuel does come out when I pump the primer but it still seems like it is starving for fuel when I try and start it. Thanks for your help sofar.

 

[ondarvr]

Re: 78 200hp johnson starting problem

Have you tried spraying premix into carbs yet? That will let you know what to work on next.