Hello, I am new to working on boat engines so go easy on me.


I have a boat with a 1998 502 mag serial # 0L017XXX. It is suddenly extremely hard to start. Hot or cold makes no difference. Throttle position makes no difference. It will start only if I use some starting fluid. It seems to run and idle fine once started. It will not restart once turned off. I can hear the fuel pump whine when I first turn on the key.


Things that were just performed:

New Plugs (CR43TS properly gapped)

New Cap & Rotor (OEM)

Oil and Filter Change

Fuel Filter Change

Impeller and Housing Replaced


I have pulled the plugs and verified spark. However, the plugs were wet with gas and very black but not oily. They looked fairly bad for brand new plugs that don't even have an hour on them. Any ideas on where I should check first?

Fuel Pressure? Just because the pump is running doesn't mean that there's correct pressure.

What is the easiest way to check the fuel pressure? Im not too familiar with this engine and I am still learning. I can go borrow a pressure gauge from the local auto parts store.

There is a brass cap over the fuel pressure test port, just above and behind the thermostat housing, under the intake plenum.

its a 502 mag mpi ? if so there should be a schader valve on the fuel rail hook the gauge on there

Was everything ok before the maintenance items above were done? Or did you change those things trying to correct this problem?

Yes, it is a 502 mag mpi. I will test the pressure as soon as it stops raining and report my findings.

Dr feelme and I where typing at the same time...........

Not the current time, and might be a type-O but should be MR43T (point on the M) gap .040
Serial number area is a MEFI -1