Need help with Mercury 75 1994

[DanDanDan]

Hi everyone.

I recently purchased a boat with a 1994 Mercury 75HP,
3 cyl 2 strokes .


Now, I could use a bit of help: the engine is really hard to start.

I will try and give as much details as I can and hopefully someone can help me diagnose the problem.

When turning the key, the motor will crank but not fire.. regardless of how many times I try to prime pushing the key

After removing one of the sparkplugs and putting a bit of fuel in there, it will start and then stall... Doing this repeatedly will eventually get the engine to start.

Once it is warm and has been running for a while.. it will start straight up. If the boat seats for a few days... Back to square one.

Both the battery and cables are brand new.
Starter solenoid is new.
Spark Plugs are new
Fuel lines are and prime bulb are new.
Fresh fuel in the tank.

Looking forward to any insight!

Thanks

Dan

 

[Silvertip]

Fast idle lever 3/4 up, squeeze primer bulb until firm, push in key and hold while cranking.

 

[DanDanDan]

Hi Silvertip,

Thanks for your reply. I should have been more specific.
I had an old mercury before and am using exactly the same method you described to try and start this engine to no avail.

Thanks

 

[Tassie 1]

Check fuel pump diaphragm

 

[Harvprov]

Can you verify the choke is working as I have a 93 75HP and if its cold it will not start without the choke engaged and working

 

[DanDanDan]

Hi,

Well, on the other Mercury (simlilar model), you would hear a click sound when pushing the key in.

This one doesn’t make any sound regardless of how long/many times you push the key in.

What is best way to check fuel pump diaphragm and choke?

Dan

 

[racerone]

It has an enricher system.----You may not hear a click.-----With motor running what happens when you push in the key ?----Motor should slow down.---If it does your cold start enricher is working properly.

 

[DanDanDan]

Nothing happens when I push the key in.

 

[racerone]

With motor running you say nothing happens when you push the key in ?----If so you need to inspect / repair enricher solenoid valve !

 

[Harvprov]

Racerone is correct about fuel enricher system in lieu of actual choke, it puts a boost of fuel to engine when key is pushed in and you likely will not hear a click of the solenid. I just happen to be doing some work on my boat and thought I woul slap the muffs on and see if it slowed down when running and key depressed and it did so I kmow mine is working and starts fine. I have a 93 75 hp Mercury tiller but pushing key in does the same. I have several Mercury motors on a couple different boats and one is an older 50 hp with a choke which you hear when key is depressed.

 

[DanDanDan]

Thanks for the help.

i have ordered a replacement electric enrichment valve.
Like I said, absolutely nothing happens when I press the key (motor running) so I am going to try and replace this part and will post results.

 

[DanDanDan]

Hi again, UPDATE:

After I put half the engine apart, I managed to test the enrichener valve and it does work...
I do not get any voltage when at the cable when pressing the key in, so maybe it is coming from ignition switch?

Also when I unplugged the harness connector, the engine side has got 8 holes but the control side of the connector only have 6 pin, (plus the trim/trim switch wires), is this normal?

I am getting a bit lost for ideas at this point but appreciate the help and advice, please keep it coming!r

 

[DanDanDan]

[No message]

 

[Roccafeller]

Probably wrong spot...couldn't find proper spot. How do I know if a used lower unit is compatible with mine. My motor is a 1983 3cyl 70hp mercury outboard. The number on the lower unit is 1643-9539