Mercruiser 160

Andy & Nick & I took his boat out one day and it worked just fine. The next day we want to go out again and this time it's being cranky. It starts fine, but it won't go above 1000 RPM and it just doesn't sound right. We open the hatch and look at it, but there are no obvious problems.

We talk about it and decide like it's not getting enough fuel, so we pop the clip off the pump's built in filter. The filter element sits on top of the pump inside a metal can. When we open it we find that there is almost no fuel inside. I would think that by pumping gasoline through this filter, eventually all the air and/or vapor would be flushed out and the filter housing would be full of fuel. But it is almost completely empty. This leads me to believe that perhaps the pump has gone bad.

The engine has almost 2,000 hours on it, so it's conceivable that the fuel pump is worn out. It's right out there in the open so we take it off and go visit the auto parts stores. Prices range from $90 at Carquest (can have it here tomorrow) to $145 at the Mercury dealer who has one in stock. The Mercury dealer suggests we check the points, so Andy drops $20 for points, rotor and condenser. We stop at the last auto parts store (Autozone) to see what they have to say and they have a fuel pump test kit they will lend us with a $150 deposit. Now is a good time to have to credit.

We install the points and put the pump back in and hook up the fuel pressure gauge. The engine starts and now it gets up to 1500 RPM, but it's still not right. The fuel pressure gauge barely gets off the peg. It is showing 6 PSI on a gauge that goes to 100. What is going on here? We call it a day and go home to eat dinner. I still think it's the fuel pump, but I had a bad experience with a fuel pump once and so my thinking is muddy, and wrong.

A check with the all knowing internet reveals that old style mechanical pumps deliver between 4 and 10 PSI, so our reading of 6 PSI is right on. The gauge is designed to handle modern fuel injection systems, which operate at much higher pressures. Don't let your equipment lead you astray.

Andy goes down to the boat in the morning and takes off the air cleaner to check on the carburetor. The choke is stuck closed. He unsticks it just by moving it manually and the motor starts and runs fine. After all this is over he recalls that there is a big aerosol can of carburetor cleaner that came with the boat. Think maybe this has been a recurring problem?

Update January 2017 replaced one missing picture. The first one is fine.