1973 85 hp starting problem

[tgjohnson1]

Hello i have a 73' 85 hp johnson with a starting problem. I have tried starting this motor every way i can think of. I am thinking that it keeps getting flooded as soon as i try to start it. I don't know if it is a carb or fuel problem. Can someone please point me in the right direction?

 

[ezeke]

Re: 1973 85 hp starting problem

You need to establish that you have good spark and good compression.

The compression test is done with all of the spark plugs removed, using a screw in compression gauge. The goal is to be consistent and record your readings for reference. The compression readings should be within 10% of each other.

Spark tests are done with all of the plugs removed, using a grounded tester that will allow for a gap of 7/16". Look for a sharp blue spark.

Then you need to have a battery capable of turning the engine at 300 RPM; that requires a fully charged, powerful battery with clean battery cables that are tightly connected.

To cold start the engine, the fuel to air ratio must be greatly increased, so the choke must be used and must close fully - 100% on both carburetors and stay closed while cranking. You need to insure this by watching the choke plates while the engine is cranked. If the choke plates are synchronized, you can adjust by moving the choke solenoid in small increments.

 

[tgjohnson1]

Re: 1973 85 hp starting problem

Thank you for that information. I have checked compression and have 135 in two and 125 in the other two. I have good spark on all four. Is there a curtain way that the fuel line needs to be run? Do you have any other things that i need to check?

 

[F_R]

Re: 1973 85 hp starting problem

Thank you for that information. I have checked compression and have 135 in two and 125 in the other two. I have good spark on all four. Is there a curtain way that the fuel line needs to be run? Do you have any other things that i need to check?

Did you check the spark with the plugs IN? You should, because it will crank slower with them in (note the comment about minimum cranking speed) It needs to crank fast enough to produce a spark with the plugs installed.

Did you check the choke? While on that subject, the choke knob on the lower front of the motor has 3 positons:

Pushed in--choke off
Pulled out--full choke
Pulled half way out (detent) Automatic position. That is where it should be for normal starting.

Fuel line position doesn't mean squat. Except the primer bulb often works better if held pointing at the sky. Once the carburetors are filled, it again doesn't mean anything.


Take one of the hex plugs out of the carburetor bottom/side. Does gas run out? It should. Both carburetors. Look at the end of those hex plugs. Does it have a coating of varnish on it? Gummed-up carburetor.

 

[tgjohnson1]

Re: 1973 85 hp starting problem

Thanks and i did. I pulled those screws out, fuel did run out and there was a brownish color on the ends of them. Does this mean that i need to rebuild the carbs? Is this what is causing the starting problem? I should have said earlier but once i get it to start, it will start back up fine.

 

[ezeke]

Re: 1973 85 hp starting problem

That's probably needs attention but is not your cold starting problem.

The starting problem is that your chokes are not closing properly or that the battery (or cables) is not strong enough to turn the engine at 300 RPM.

Just take the air silencer cover off and watch the choke plates while you crank the engine. They have to stay 100% absolutely closed until the engine fires.

One other thing, be sure to use the warmup lever - it advances the timing. If you don't have one, you need to find a way to advance the throttle lever for a cold start.

 

[F_R]

Re: 1973 85 hp starting problem

That's probably needs attention but is not your cold starting problem.

The starting problem is that your chokes are not closing properly or that the battery (or cables) is not strong enough to turn the engine at 300 RPM.

Just take the air silencer cover off and watch the choke plates while you crank the engine. They have to stay 100% absolutely closed until the engine fires.

One other thing, be sure to use the warmup lever - it advances the timing. If you don't have one, you need to find a way to advance the throttle lever for a cold start.

Ah yes, the warm-up lever. Excellent point. If you don't use it, it will be nearly impossible to cold-start. Which brings us to the question that should have been answered right away---what kind of control are we talking about here? The Evinrude and Johnson side mount controls have the warm-up lever. Binnacle controls use a variety of ways to do the job, but they all have some way of getting the job done. Finally, the throttle cable needs to be adjusted correctly.

EDIT: Just one more thing. The 1973 has the two stage electric choke. BOTH stages have to be energized to hold the plates closed tightly enough. If there is an electrical problem in the choke circuit, they will close weakly. There was a service bulliten about re-wiring the choke. Nevertheless, it remains that both stages have to be energized for cold startup.

 

[tgjohnson1]

Re: 1973 85 hp starting problem

Thanks, I'll check that this afternoon. I have a side mount Johnson controls that has a warm up lever, and it has a electric choke on it but i dont think that it is working. I have been just using the one on the front of the motor. Do ya'll think this is going to need to go to the shop to get fix? Thanks again for that info.

 

[ezeke]

Re: 1973 85 hp starting problem

The choke solenoid had two ways of operating, but many of them were rewired by service departments in the 1970's.

The automatic choke function worked by a temperature switch located next to the lifting eye at the top of the engine - you can verify that by checking for the wires.

The other way was to use the toggle switch located on the remote control while the ignition switch is in the run or start position.

In rewiring, both wires were routed to the toggle switch so that full power was delivered to the solenoid.

Please click the thumbnails.

After the service bulletin the automatic choke was discontinued on the newer models, suggesting that OMC had done away with the concept. I personally feel that they should all be disconnected and rewired so that the toggle switch gives maximum direct control to the operator.

 

[tgjohnson1]

Re: 1973 85 hp starting problem

Thanks for all the help from all. I think I'm on the right track. The starting problem was the choke linkage. It was not closing all the way. I still have a few things to finish but it will start up now. Thanks again

 

[ezeke]

Re: 1973 85 hp starting problem

Thanks for the feedback - it helps.