Still having problems starting my 73 115Hp johnson when it is cold

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teslaman

Petty Officer 2nd Class
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I've changed spark plugs, performed a de-carb, and experimeted with the fuel mixture, and fixed the choke -- all with no results, the motor will not start easiliy when it is cold.

Once the motor starts it runs great. I'm going to check compression just becuase everything else has failed. I would have checked it earlier except that the motor runs so good when it starts that I didn't expect it to be an issue.

I've only owned the boat for about 4 months, so I may not have a point of reference for how good the motor runs, but it has good acceleration and smooth running. I did notice that the ingnition system runs off a group 31 deep cycle instead of a starting battery, could this be ab issue?
I did notice that the battery
 
Silvertip

Silvertip

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Re: Still having problems starting my 73 115Hp johnson when it is cold

The battery is used only for starting. It has no bearing on engine performance once its running. If you haven't checked compression, do so now. Low compression can cause cold start problems. Is the choke functioning properly and are you using it properly. Hold the choke until the engine fires. Then release. Are you pumping up the primer bulb before attempting to start.
 
T

teslaman

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Re: Still having problems starting my 73 115Hp johnson when it is cold

This is why I wonder about the battery. I fthere isn't enough cranking amps, there may not be enough of an arc to fire a cold motor. After its running, its almost self sustaning.

As far as the choke and priming bulb go, I'm doing both of those things.
 
Theoutdoorsman

Theoutdoorsman

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Re: Still having problems starting my 73 115Hp johnson when it is cold

I had a problem, EXACTLY like this, with one of the older in-line mercury's. I'd run a battery way down trying to get that thing started initially. Once started and warmed, it seemed to start with the turn of the key the rest of that day. It turned out to be a weak starter. I am not at all familiar with your ignition, but if all else fails, rebuilding the starter might be something to look in to. Just a thought....................... ALAN
 
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ezeke

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Re: Still having problems starting my 73 115Hp johnson when it is cold

The battery is key. The 73 service manual specification says 200 RPM, But the next year they changed it to 250RPM and they still needed more power.

We found 300RPM was enough to get get full spark when cold, and that takes 650cca or better in a good dual purpose deep cycle battery, fully charged. That will do the job consistently.

Anything less and you will be disappointed.

Starting batteries cannot take the frequent deep discharge and consequent recharging that an occasional user subjects the battery to with these old motors.

Even if you run it every day, it will require frequent recharging because the little rectifiers can't do the job.
 
T

teslaman

Petty Officer 2nd Class
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Messages
196
Re: Still having problems starting my 73 115Hp johnson when it is cold

Thanks for the tip Alan, that's something to look into. Is there a way trouble shoot the starter before rebuilding it?
 
Silvertip

Silvertip

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Re: Still having problems starting my 73 115Hp johnson when it is cold

There is a simple way to tell if battery power (or lack of it) is the problem. Try using two batteries. If it still doesn't start, battery power is not the issue. As for the starter itself, you'd need a fluke stule meter to measure actual current draw. If its higher than spec, the bearings may be tight, the armature dragging, shorted winding, etc.
 
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ezeke

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Re: Still having problems starting my 73 115Hp johnson when it is cold

Are you a betting man Silvertip?
 
T

teslaman

Petty Officer 2nd Class
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Messages
196
Re: Still having problems starting my 73 115Hp johnson when it is cold

I've looked at the battery specs, but I can't remember them off the top of my head. I'll go and look to see if the batt is rated for at least 660 CCA. I've got another deep cycle batt comming to I can test with it also.
 
tashasdaddy

tashasdaddy

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Re: Still having problems starting my 73 115Hp johnson when it is cold

make sure it is fully charged, and doesn't have a dead cell. they can be load tested at the auto parts store for free usually.
 
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