Have u checked the fuses? 

Post

Have you checked that your start solenoid is getting 12v when you turn the key to start?

Also, do you have an isolator? If so what type? Could be corrosion in the isolator meaning you aren't getting a decent enough connection when it comes time to crank the motor. 

 Unsure on the fuse its a 1975 outboard if it has a fuse i wouldn't know were it is and i dont think it has an isolator, i am yet to check voltage as i havnt got a multimeter gonna try and source one today

 Check for power coming to the solenoid when the key is turned, as recommended above, but considering that you choke button does not work too, seems like the keyswitch is not working.... first check your connections to the control box from the motor, then the connections from the motor, and of course the fuse and isolator, if there is one - google for an electrical diagram for your model motor, that will indicate all the connection points, fuses and color wires to check.

If you are not sure of electrics, use a test light rather, about $5 at supacheap, to test for power..., then get a mate around with some electrical knowledge.. mistakes on the electrical system can get expensive..

...and back to basics - first check your battery connections are good and tight..

Hope that helps mate..

 http://www.justanswer.com/boat/58xv8-i-m-looking-wiring-diagram-1984-mercury-115hp.html#re.v/458/

scroll down for the wiring diagram..

 Check the main line from the battery to the solenoid.  If it has heat shrink on it at the ends peel it back and make sure the wires are not corroded in the lugs. This is a common problem especially if someone hasnt used tinned copper cable and used standard battery cable and being that old has probably been replaced before.  

I had the same symptoms with a mariner 115hp and it was the solenoid. Cheap easy fix.

edit- Re-read, you changed solenoid, its not that then!

Thanks guys i have finally put a multimeter on the outboard and i seem to be getting power to it. But basicly on my solonoid i have the power goin in and power out i also have 2 smaller wires black and yellow now when i touch the power in and the yellow i get 12v but when i try to start it drops to .40v and if i touch the power out with the black i get 11.7v but if i try to start i get 12.4 or somthing could it be the solonoid as the other solonoid i tried is not new. Hope that made sense cant understand why my choke button doesnt work but i have checked all leads and everything seems fine.

Ok, your post is a little confusing, however I think you are using your multimeter wrong. 

You want to put the tip of the black lead on the main engine negative bolt (follow it back from the battery). Keep it there. 

Now what you should get without the key turned  is 12v on one side of the main power leads. The yellow wire shouldn't have 12v, neither should the black or the other side of the solenoid. 

When you turn the key the yellow wire should get 12v and you should get 12v on both sides of the soleniod power leads. 

I hope this doesn't come across me being a prick.. Just tryin to help. 

Steve 

 Hey steve not at all its exactly what i need will try this tomorrow 

No worries mate.

Obviously the things I said that will happen when you turn the key will only happen while the key is held in the start position.

 Bridge out the solenoid main terminals  with jumper leads.  It may/will  spark at you but will tell you that the power getting to the solenoid is good enough. 

ok so I had a look today and I put the multimeter black lead on my main earth coming from the battery, my main power coming in to the solonoid has 12.6v but the yellow, black and power coming out have 11.9v and so does the earth coming from the starter so I am totally confused dont know what is goin  on, I even touched the main earth and put the red meter wire on the body of outboard and that shows 11.9v

WTF!!!! do I have a short somewhere, if so how has this happened in the short drive from house to marina???

Hey Shane, sounds very odd!...

so this is all with the key in the off position?

i take it you are keeping your black lead on the main earth and then touching the red lead to power in to get 12.6v? Then touching red lead to yellow and getting 11.9? Then red lead to other side of soleniod and getting 11.9 aswell?

If possible, try and find somewhere on the engine where a a black wire is bolted to the head with an eyelet. This should also be an earth. Then use that bolt to keep your black lead on and try again. 

Steve 

 Got Any Sparky mates?  Or Take it in to a mechanic.  They will probably sort it in 5 minutes.  

 I am checking it in the on position as in turn the key once but needs one more turn to start 

 Can you post a pic of what your lookin at.   Then we can tell you what to check. As a sparky what your sayin makes no sense.  There is more than 1 relay on a motor but if its the starter relay  it should have a fat cable coming straight from the battery to one side of the relay. On the other side there should be one fat cable going to the starter motor.   Check the voltage to the relay with the key off.  Turn the key to the starting position as if you were turning the motor over and check the voltage either side of the relay.  

As above, that doesn't make a lot of sense.

One thing you can do though is test that the main earth is actually earthing the motor. There is a setting on the meter that will make a buzzing or continuous beep sound while you hold the tips of the red and black leads togethor. Once you have your meter on this setting put the tip of one lead on the main earth bolt ans then touch the bolts on the head with the other (you may have to scratch some paint off to get a good contact) it should make the buzzing or beep sound each time. 

Sounds like an earth issue to me. 

 Yeh will take some pics soon, i believe it to be a earth issue as well as i have had the same issue before but found the loose earth this one not so easy

 Ok my progress so far or should i say no progress i am still yet to find the problem i am at the point now i am about to start replacing wires and cleaning every terminal, the only thing i have found is that when i turn the key and hear the clicking i am getting no power to starter motor but why do i get power when the key is off, i have another solonoid will try that tomorrow other than that i am out of ideas, could be time to cough up some cash.

Hi Shane

Did you check the Earth cable from the battery to the motor?

Another one to definitely check is that your kill switch on your control box hasn't been flicked to the off position.

Steve

 Yeh ive checked that cleaned it tightened it retightened it haha i dont think it has a kill switch 

 Ok so i did a continuity test on the positive and negative  leads when disconected and have found i have a complete circuit so can only assume all is good from battery to engine but also noticed when i turn the key to turnover position the current drops does this mean it is a problem with the switch or wiring to switch?

Shane are you able to take any photos of the solenoid and the control box? What colour are the large cables coming from the solenoid?

Or even provide a serial number so I can find the correct wiring diagram?

Also, does the black lead from the battery run directly to the motor or does it go to the wiring harness? and does the red lead from the battery do directly to the start solenoid or to the wiring harness?

Steve

 How do attach i photo

Are you able to do the tests you have already done but use the negative post on the battery as your main point for your black lead? It may be a struggle depending how long your leads are. 

And as above, do the red and black leads go directly to the motor or to the wiring harness?

Yes red and black go straight to motor as for tests i will try that tonight 

Hmmm ok, I'm just trying to figure out what control box wiring to look at... It will be interesting to see if you get the same readings tonight because what you're saying at the moment is that when the key is in 'run' the whole outboard is live. 

Where abouts are you located?

 Merriwa near clarkson im so confused haha

I have finally cracked it, it took me 2 bloody weeks but I have finally found the problem, It was an earth all along as i thought just couldnt find it.

I put a jumper lead from earth at battery to earth at starter and turned the key and it fired up, i cleaned the earth lead connected to the body of motor and still didnt start

so seems I am not getting a good earth from the battery to body, so tommorrow I will be cleaning all leads.

Thanks to all that helped out and gave me ideas, especially sstevee cheers mate so stoked now I just need some good weather.

Sweet! Good to hear Shane. I think it may be the earth lead from the batt to the body of the outboard itself. Even if you are getting continuity it doesn't mean that the lead is in good condition.

You can test this with your jumper cable too. Disconnect the lead at the battery and use the jumper lead in its place. If it starts up then you know the lead is dodgy.

Good luck