2007 Mercury Optimax 75 HP ELPT

[Lerodrick24]

Good afternoon all. I am having some issues with my boat and I am looking for the community to help me.

The issue I am having is that my boat will not start. The engine will turn over but it will not catch. The issue has to be within the air system. The spark plugs are new. The boat has gas in it. The injectors are new. The ignition coils are new. Today. I replaced the air diaphragm on the fuel rail. I thought that was the issue. But the problem continues. The pumps inside of the fuel/water separator are working. What do you guys think my problem can be? Open to any suggestions at this point. I took my boat to a shop and I paid over 600. Dollars in hours alone. Just to not have a working boat.

 

[kbonanny]

Will it run an an alternate fuel source? Do you have spark? How do you know the injectors are being pulsed?

The first is to ALWAYS start with the basics. Have you run a dry and then a wet compression test on the engine yet? An engine with low compression can have all the air/fuel & spark on earth but won't run, period. IF you have compression (*even on all cylinders and within specs*), then proceed to seeing if you can't figure out which of the 3 that's missing, air/fuel or spark.

Start with an alternate fuel source. Remove the air intake, have someone crank the engine while you spray in SMALL AMOUNT of Berkible 2+2 carburetor cleaner. BE CAREFUL TO NOT SPRAY PAINTED SURFACES as carburetor cleaner can remove certain types of paint! IF the engine sputters like it's trying to start when you do this, the problem is on the fuel side. If not, after a couple of attempts, pull a plug to see if they're wet. If they're wet, ensure you have spark.

With the minimal information you have offered here and without seeing the outboard personally, anything else I say is a guess. This world functions on having as much information at your fingertips as possible.

 

[QBhoy]

Battery be the first thing I’d suspect.

 

[Lerodrick24]

Update:
So I tested for spark and they are bright. I ran a separate fuel system to the boat and nothing. I did the fuel and air regulator tests and they were within the specifications of the manual. I took the boat to my friends house and he overlooked it with me. He noticed my battery was not 100 cranking amps. So he put his battery in it. Then it fired up and ran good. I went the next day and bought the same battery. Made sure it was charged and the boat did the exact same thing as before.

 

[Lerodrick24]

Will it run an an alternate fuel source? Do you have spark? How do you know the injectors are being pulsed?

The first is to ALWAYS start with the basics. Have you run a dry and then a wet compression test on the engine yet? An engine with low compression can have all the air/fuel & spark on earth but won't run, period. IF you have compression (*even on all cylinders and within specs*), then proceed to seeing if you can't figure out which of the 3 that's missing, air/fuel or spark.

Start with an alternate fuel source. Remove the air intake, have someone crank the engine while you spray in SMALL AMOUNT of Berkible 2+2 carburetor cleaner. BE CAREFUL TO NOT SPRAY PAINTED SURFACES as carburetor cleaner can remove certain types of paint! IF the engine sputters like it's trying to start when you do this, the problem is on the fuel side. If not, after a couple of attempts, pull a plug to see if they're wet. If they're wet, ensure you have spark.

With the minimal information you have offered here and without seeing the outboard personally, anything else I say is a guess. This world functions on having as much information at your fingertips as possible.

So update. I had bad diaphragms. The new ones they mercury provided did not give me the correct cranking pressures. So I now have a new fuel rail and the pressures are correct. Fuel is around 14-16 PSI over air and it’s around the 94psi range. So. I replaced the battery with one that has 1000 cranking amps. I am going to try an alternate fuel source and see if that fixes anything. Will report back.