Yamaha F115/Mariner 115 EFI won't start

[twirk_twirk]

Hey Ya'll hope you're having a wonderful summer. I myself am out boating when weather and time permits and on the side I am working in the shop to get my spare Mariner 115 EFI to start (This Mariner is the same as the Yamaha F115).

Here's the problem:
I've had this engine for a few years and it has been in indoor storage and not in use. It is a used engine and it has some problems. before (meaning a few years ago) it would start and run just fine in the shop. However now it won't.

It cranks and cranks but never starts.

I've got gas in the system, fuel lines are clean. I have spark in the spark plugs. Oil is topped up. If I crank the engine without spark plugs I can smell gasoline pumping out of the cylinders.

I find when I crank the engine for longer than approx. 4 seconds the warning buzzer sounds in the remote control unit.

I've been hooking up a battery using regular car booster cables.


Do you guys have any suggestions as to what might be my problem?

[boscoe99]

The warning buzzer in a Yamaha will normally sound if the motor is cranked with the kill switch activated. Of course with the kill switch activated there will be no spark.

I have not a clue about a Mariner 115 EFI. I had a Mariner 175 EFI but that was a two stroke made by Mercury.

[twirk_twirk]

thanks boscoe99.
I can see in the shop manual that a weak spark can also be caused by corrosion at the stop/lanyard switch. Next time i'm at the shop I'll try to fiddle with that a bit. See if it makes a difference.

[rodbolt17]

I would start with a compression and spark test.
then check fuel rail pressure.
the 4 stroke f115 Yamaha was used by mercury for a few years,

[twirk_twirk]

Hi Rodbolt17,
Thanks I'll try those.

I've done the compression test. All cylinders read between 160-170psi. So that is pretty good I think.

When I turn the ignition key half way I can hear the High Pressure Fuel Pump start up, but it doesn't seem as loud as on my working Yamaha F115 (my other engine).

If I pull out the spark plugs after I have cranked the engine for a bit, the spark plugs are dry.

Would the fuel rail pressure be at proper level even when cranking? (I do have a pressure tester for that) I ask because I can't get the engine to start and am wondering whether if there would be a reading from a pressure gauge attached to the fuel rail when just cranking.


I don't think I'm set up to do a spark test. I'll have to look into how to do that.

[rodbolt17]

google" homemade spark tester".

rail pressure will be there at key on.

its a stupidly simple EFI.

[twirk_twirk]

I've basically tested each spark plug by holding them individually to the frame of the engine. They all have spark .

I think you're on to something with the fuel rail pressure. I'll test it today or tomorrow. I think the vst pump might be shot because the sound I hear from it now is weak compared to my other yamaha engine. But a pressure test can confirm that.

I'll be back.

[twirk_twirk]

I forgot to mention another important symptom. When I try to trim the engine the relay only clicks. The engine doesn't move up or down. Could there be some electrical problem ? Everything looks normal when I hook up the yamaha YDIS software as you can see fromthe screenshots

[twirk_twirk]

Plenty of spark.

There's no pressure at fuel rail. I do hear the high pressure fuel pump cycling when I turn the key. However no spike in pressure whatsoever also my engine trim does not move. I only hear the relay clicking, but no movement or noise from the hydraulics of the engine trim.

[twirk_twirk]

Hmm, I posted several replies, but they got deleted somehow... Here we go again.

So, I tested for sparks. Lots of spark.

I test pressure on fuel rail. Nothing. I can hear the high pressure fuel pump spin up when I turn the key to on, but nothing happens on the pressure gauge. no pressure

Also, another problem that leads me to think there might be an electrical problem is that the engine trim doesn't function. All I hear is a 'click' from the relay when I push the trim button up or down.

I've attached my reading from the YDIS software. Everything otherwise, seems proper.

[twirk_twirk]

more YDIS reading.

[greasyshaft]

If you have no fuel pressure there's your problem.
If the engines been sitting so long it's probably got gummed up fuel system.
Solve your power supply problem to the engine if there is one, easily tested with a multimeter. Also check voltage at pump, FYI the ECU switches the earth.
Open VST drain and pump primer bulb, make sure you actually have fuel at the VST.

[twirk_twirk]

Thanks greasyshaft.

Could very well be the fuel system is gummed up. I've opened the VST drain and can confirm there is gasoline in the VST. Perhaps the high pressure fuel pump is gummed. Next time I'm at the shop I will hook up a primerbulb (don't have one yet) and make sure the VST is full of fuel.

I can't really find the voltage specs for the high pressure fuel pump. Do you know what the multimeter should read when I hook it up to the fuel pump wires? (my uneducated guess would be 12v)

I don't quite understand what you mean by the ECU switching the earth? Do you mean I should switch the red and black multimeter wires when testing the engine?

Do you think it's possible that the engine powertrim problem (both cowl trim switch and remote control trim switch only make the relay click) and the VST pump problem are related? Or no?

p.s. uploaded larger images

[rodbolt17]

at key on the main relay suppies 12V to the pump and injectors.
the ECU provides the ground path(earth) to operate the deviceits a simple 12v motor.
if you ever cut one open it will scare you.
the gasoline actually flows over the motor windings,brushes and commutator before exiting the pump.

[greasyshaft]

Thanks greasyshaft.

Could very well be the fuel system is gummed up. I've opened the VST drain and can confirm there is gasoline in the VST. Perhaps the high pressure fuel pump is gummed. Next time I'm at the shop I will hook up a primerbulb (don't have one yet) and make sure the VST is full of fuel.

I can't really find the voltage specs for the high pressure fuel pump. Do you know what the multimeter should read when I hook it up to the fuel pump wires? (my uneducated guess would be 12v)

I don't quite understand what you mean by the ECU switching the earth? Do you mean I should switch the red and black multimeter wires when testing the engine?

Do you think it's possible that the engine powertrim problem (both cowl trim switch and remote control trim switch only make the relay click) and the VST pump problem are related? Or no?

p.s. uploaded larger images

Check for power to the T/T motor, Probe blue and green wires when pressing up or down when you press up the blue is positive and green is negative,vise versa for down. try tapping the the motor with something (preferably not a sledge hammer) if you have power to it, sometimes the brushes stick.

Sorry for the crappy explanation just got back from the pub