1996 Merc 125 ELPTO - Bog down after WOT

[itxpt]

I can start the motor fine, it will idle endlessly fine. When I take off, it flat out goes and gets on plane smoothly, I can cruise WOT for about 1 minute, and then I can feel it loosing power, I lower the lever to idle and it will idle, I can wait a few minutes and start that process all over again.

I've changed the fuel filter, prime bulb and have recently rebuilt the Pump Assembly Accelerator. I took apart and examined the fuel pump and it seems ok (but I'm no expert).

My next steps in troubleshooting is going to be bypassing my gas tank in the boat and using an external one. I'm hoping to get some more ideas on what I could be missing.

--Steve

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[Dave1027]

Sounds like it might be getting starved for fuel. Did you check the state of the primer bulb when it happens? Was it collapsing? What happens if you squeeze the bulb when it happens?

If the fuel pump was never rebuilt, it should probably be done regardless.

 

[itxpt]

I have not checked the state of the primer bulb, however if it does die after the bog down, it will start up and idle fine. I will check it out though. I think I will get the parts on order to rebuild it.

 

[itxpt]

Do you happen to know if this is what is required for the rebuild?

Fuel Pump Diaphragm Kit - https://www.crowleymarine.com/parts/276.cfm

 

[Dave1027]

Do you happen to know if this is what is required for the rebuild?

Fuel Pump Diaphragm Kit - https://www.crowleymarine.com/parts/276.cfm

That looks like it. It has one extra gasket that mine doesn't have (the one on the top left) but my motor is older than yours.

 

[Dave1027]

I have not checked the state of the primer bulb, however if it does die after the bog down, it will start up and idle fine. I will check it out though. I think I will get the parts on order to rebuild it.

A collapsing primer bulb would indicate a blocked fuel line to the tank or a block tank vent. If the bulb is fine but when you pump it the rpms pick up, that would indicate a fuel pump issue.

 

[itxpt]

Thanks, I ordered the kit and will take the boat out today and check the bulb.

 

[itxpt]

Took the boat out this afternoon, started up fine, got past the no wake zone and went WOT, got on plane and cruised for about 30 seconds, then I felt is dying and got off the throttle, it did die. Strange thing now is that when it does that I have what seems zero power to the ignition and motor tilt. Turning the key does not make the initial beep and acts as if there is no power. After sitting for a bit it end up working again. I ended up switching to an external temp tank just to bypass my tank and fuel. the boat started ad I let it idle for 30 mins, then decided to see how it acted under load. Under lowish RPM it did great, I got on it a bit and noticed it was going to die so I let off and let it continue to idle and just headed back to the dock.

I have the fuel pump rebuild kit arriving tomorrow and it will get it going. Now I'm just wondering if going full WOT and then it dies and I have no power to ignition, if that is just another issue or if it is related.

 

[Dave1027]

First thing to check is your battery connections. Power to the starter and tilt comes from the battery. The power to run the spark plugs comes from the magneto. The rectifier is between the battery and the magneto. Maybe the rectifier going bad?

Does your boat have a volt meter gauge? What is it reading when it died?

 

[itxpt]

It does have a volt meter, after it died the gauges were pegged to the high side of the gauges. Once it started it again it was showing 12 volts. I'm going to go through the electrical after I rebuild the fuel pump.

So strange that it "seems" to just fix it self after waiting a bit.

 

[Dave1027]

It does have a volt meter, after it died the gauges were pegged to the high side of the gauges. Once it started it again it was showing 12 volts. I'm going to go through the electrical after I rebuild the fuel pump.

So strange that it "seems" to just fix it self after waiting a bit.

That's the way electrical issues usually start. They go "intermittent" first due to a bad connection. It can be temperature or vibration that may cause it to act up and then mysteriously fix itself.

Pegged gauges definitely indicates a serious electrical issue. Maybe a bad ground connection?

 

[itxpt]

Rebuilding the fuel pump was to fix for the stall outs. And I did find some battery connections that are kind of corroded and one was loose so that was triggering the boat not starting again. So I think I'm in good shape at this point now. Thanks for all the input.

 

[itxpt]

So now I have an issue that occurred when I had the battery issue and the problem is that I cannot tilt the motor up from my control box at the driver seat nor can I do it from the bow of the boat. I can however go down from the driver's seat and from the bow and directly on the motor up and down works, for the life of me I cannot figure out why up will not work and the other two locations but down does.

 

[Dave1027]

You can tilt the engine from the bow? When would you need that functionality?

It's sounds like a wiring connection issue to the controller. Tilt down works so that means the control is getting 12v. The controller should be putting 12v on the blue/white wire to activate the trim up solenoid.

 

[itxpt]

yeah my nitro 185 has it at the bow also. after I posted this last night I started poking around with my voltmeter and the middle solenoid wasn't getting 12 volts and I would shake it or kind of move it and then it would get it and work so I'm pretty sure it's slowly dying. I ordered two of them just to replace both of them that are in the engine.