125 HP Mercury Quits

I just bought a boat with a 125 HP Saltwater Mercury. I had it tuned up and it ran great (other than slight issue with idle speed).

I towed it 1500 miles, put it in the water and now it will die after running for 5 minutes or so. I haven't had a chance to open it up - so I'm wondering if it's related to the slight idle speed issue I had. But when it dies, it doesn't want to start up again.

I did notice that the fuel line was crimped a bit when I had the motor trimmed to get out of shallow water. When I uncrimped the line - it started and ran for about 5 minutes. Then died again.

I finally got it to the mooring, let it idle for 5 minutes, it died and would not start again.

Any ideas?

Re: 125 HP Mercury Quits

There are lots of possibilities for a motor to bog and quit. While the symptoms you describe make it seem likely that you have a fuel supply failure, rather than an ignition failure, it is usually a good practice to first confirm this before doing much of anything else.

Use a spark tester or timing light to check whether the spark is failing when the engine bogs/quits. If the spark is not failing, try squeezing the fuel bulb when the engine bogs/quits to see if that helps. You can also try spraying some fuelil (50:1) mix in the carb throat during engine bog/quit to see if that helps. Alternatively, you can hook up a vacuum gauge to the fuel line to see if the fuel lines are restricted or if the fuel pump is failing. If any of these tests indicates that you have a fuel related problem, you can go from there. I find that the vacuum gauge test is the most definitive.

Having said all this, you might consider just going ahead and rebuilding the fuel pump and checking if your fuel tank vent is restricted. These are common causes of engine bog/quitting if it happens regularly and soon after the motor has run for just a few minutes.

good luck