mercury 90hp wont run

[lynnboy021]

i have a mercury 120 3 cyl f14 sea ryder jetboat and i already installed new red stator, new plugs and rebuilt fuel pump.... so my problem i am having is that the motor just cranks and cranks it does not wanna start...... carbs was just rebuilt a week ago by a pro and i have 120 psi on all 3 cyls and yes i do have spark..... i got her running one time and if i give it gas she just stalls out but will restart fine but the next day she will not start up for the life of me......

 

[enginepower]

Do you pump the bulb until firm and use choke when trying to start?

 

[lynnboy021]

Yes... there is no choke on this boat it has a automatic choke or whatever it's called, it just gives extrabgas to the carbs

 

[lynnboy021]

So no one knows what it could be??

 

[DavidMoore]

Could be many things. Sounds like a fuel issue though

All the things you had done was to solve the issue, or did the issue start after you did all those things?

Your right the engine does not have a choke as such, but I think enginepower was talking about the enrichener system. If yours is the same 90 HP 3 cyl engine as mine it's not automatic; are you following the correct start procedure : primer bulb hard, fast idle lever set 1/2 way, turn key to crank the engine then push the key in into "choke" as it's cranking. - Do not let crank for more than 10 seconds, give it 30 seconds break before trying again). If everything else is OK engine should fire right up,

Here is a nice list of other possible problems
1 Fuel tank vent closed / blocked.
2 in line fuel filter / water separator / fuel pick-up in fuel tank blocked.
3 Loose hoses especially in combination with 1 and 2.
4 Old Fuel lines failing / restricted on inside.
-- install a clear plastic pipe between fuel pump and 1st carb, crank the engine and see if your pumping fuel or if your pumping air bubbles / also try running from a separate fuel tank. If bubbles find and repair the blockage / leak.
5 Enricher valve not functioning - check engine makes a clicking noise when the key is pushed in, if no clicking noise can be heard the enricher valve has failed / is not connected and will need fixing. If you can here a clicking noise remove outlet hose from enricher valve and place suitable container to catch the fuel under the outlet, push in key and check fuel flows from the valve to check it's working properly.

6 Do you have an Anti-siphon valve? If so remove it and see if there is a difference

Here are some other things which might sound dumb but you never know.

Throttle not set up correctly, the cam on the center carb "overcentering" so all the carbs do not close from the wide open position (this happened to me once) :blue:
Carb's are in sync with each other, they all open and close with each other and by the same amount.
Have you checked the ignition timing
Kill switch not in run position, happened to a mate of mine once and he called for a tow home :laugh:
HT leads not connected to correct plugs.
Low speed mixture screws not set correctly (should be 1 1/2 turns out from lightly seated for initial start-up following carb re-build)

Good luck.

david

 

[lynnboy021]

hi david um i made a mistake on my boat info, it has 4 cyls with two carbs and its a 2 stroke and the serial number for the motor is 0E125495.....

1. Not sure.
2. all new
3. all new and tight
4. all new lines and a rebuilt fuel pump BUT the line coming from the fuel pump to the carbs does have a bubble but dont know why when all lines are tight and new....
5. i dont know if i can push the key in...
6. not sure...
7. i did not check timing, i am going to do it in a few...
8. not sure if carb is 1 1/2 turns out...

to me i really think its a fuel problem, when i remove the plugs the plugs are really clean and dried......

 

[DavidMoore]

Your engine serial number comes up as a 120HP 4 cyl engine, I have little experience.

So forget point 5 and the starting procedure because you are right, it is an automatic enricher system.

Important to note for the enricher system is the carburettor shutters must be completely closed (not even slightly cracked open) when trying to start the engine otherwise air will be drawn though the carbs and not the enrichment valve. So maybe worth checking this.
You can test the automatic enricher valve by measuring the resistance across the yellow wires, it should be between 18 and 20 ohms with a cold engine. This will change to infinity after about 2 mins of the engine running.


Other things I picked up by reading other threads.
Make sure the engine is fully trimmed in before trying to start.
Get the primer bulb really really hard.

Lastly and about the only other thing I can think of is cranking speed, does the engine crank over really fast on the starter motor? If not the starter might be drawing too much current so even if the plugs fire outside the engine, they don't inside the engine.
Check all electrical connections are nice and tight and free of corrosion, if all connections are nice and tight and corrosion free and the engine does not crank really fast consider stripping and cleaning the starter motor, it's not difficult and made the world of difference on my engine (starts now 1st time, not 8th 9th or 10th attempt like before).

Good luck

David

 

[lynnboy021]

So I did everything you said to do and she still does not wanna start... I check the timing and I can't get the timing to 30 only 15 and the spark only stays on for a few then turns off then flash then off then stays on......

 

[DavidMoore]

Strange.
Did you check the timing with the throttle shaft at wide open throttle (WOT) position (should be 32 before top dead center at cranking speed).
If the throttle shaft was at WOT and you can only achieve 15 degrees something is very wrong. I would check the flywheel key is not sheared off or was not forgotten when the stator was changed.

The other concern is you say your plugs are really clean and dry. Have you tested to see if the auto-enricher squirts fuel when the engine cranks.

 

[lynnboy021]

So I was looking at the motor today and I found the problem... the problem was a black/yellow wire on the switch box was grounding itself... so I taped up the wire and problem fixed...... thanks all for your help

 

[DavidMoore]

Well done you.
:clap2: