1999 Mercury Pro Max Super Mag 225 Won't Start

**Aimee Lane** · 06-02-2020, 10:53 AM

So we have a Blazer 210 Pro V with Merc 2.5. Motor ran great driving up lake and died like you turned switch off and wouldn't crank back. Would turn over but not fire. Checked spark plugs they have fire, replaced fuel pump and no change...gauge is showing 39 psi. You can spray gas back in the motor and it will run. Anyone have a clue? Could it be bad ECU? Also how do I test injectors to see if they're getting power?

**idvette** · 06-02-2020, 11:48 AM

Check where the injectors plug into the ECU, should be a round 4 wire connector. Check for power, corrosion, and wiggle test.

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**Aimee Lane** · 06-04-2020, 09:03 AM

Injector harness had power. He hot wired injectors and you can hear them firing. After doing this the motor cranked right up and thought we fixed it, maybe stuck injector. So after setting for several hours it wouldn't start back again. This morning hot wired injectors again and it started up again. Sound Like injector problem or something else?

**idvette** · 06-04-2020, 09:11 AM

Sounds like a wire issue. Most likely the hot wire to the injectors shorting, poor pin fit in the connector, or broken internally somewhere. While it's running, wiggle and pull on the injector harness and connector, should be able to narrow it down.

**Aimee Lane** · 06-04-2020, 09:22 AM

Just inspected plug everything looked fine...cranked motor back up, wiggled plug and motor kept running didn't seem to be a short anywhere. Gonna let motor sit few hours and see if it will still crank. Definitely puzzling as to what the issue is. Can't get it into boat shop to have it checked for 3 1/2 weeks they have a waiting list hoping to fix the issue before then. That's a long time to be off the water lol

**Aimee Lane** · 06-08-2020, 09:05 AM

After we hot wired the injectors 2nd time, inspected the wiring harness and all that, fired the boat multiple times next couple days and seemed fine. Took it to the lake yesterday fired right up so tried a test run. Boat idles fine and runs at high rpm fine but when you start coming off a plane down to a lower rpm the boat hesitates like its going to die, mash the throttle back down and it hesitates then it will pick back up and take off as if nothing was wrong and run fine. Its almost like its not advancing time?

**idvette** · 06-08-2020, 09:12 AM

Strange, maybe someone else will chime in. Injector driver in the ECM? Or ecm losing crank signal? Hard to say without it right in front of me lol

**Aimee Lane** · 06-21-2020, 07:46 PM

Ok so took boat back to the lake today and after running down the lake about 1/2 a mile was going about 50 mph the boat died like you cut the switch off again. After getting back home looked at motor and checked the plugs again and plugs 1, 3 and 5 have no fire! What would cause this...could it be the inner switch box?