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95 Merc 200hp Blackmax weird fuel issues.

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  • 1 Post By EMC Pursuit

95 Merc 200hp Blackmax weird fuel issues.

Old 09-13-2019, 05:54 PM
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Default 95 Merc 200hp Blackmax weird fuel issues.

1995 Mercury 200hp 2 stroke Blackmax. I realize now that I am having fuel issues. Very recently I replaced both fuel/water filters. Cleaned out a nasty VST, drained all the gas from plastic tank and inspected what came out. It was all fresh gas with no water and the tank looked clean, pumped all new gas into tank. Also replaced all new fuel lines, inspected the fuel pump and gaskets looked rather new (perhaps previous owner recently rebuilt it). I ran Seafoam thru the motor to clean out injectors. I did not get a chance to test and clean out injectors. But boat fires right up, idles great. First trip after overhaul was 38 miles trouble free with only one hard start. Second recent trip 2 weeks later I went off shore the first 35 miles problem free and boat ran great. THEN 1st stop boat did not fire up as smoothly and took several attempts. But did fire up to move to next tuna spot and shut it down. Repeated 2 more times with similar results where it took a few extra long cranks to fire up. Last time, battery one drained from running electronics. Switch to battery two and that would not start it, some times I would get a click sometimes I get the motor to turn but not fire up. I thought it was a bad battery or drained battery. So I go to 3rd battery which is brand spanking new pull out battery number 2 and hook up new batt and try to fire up motor. Same thing and would not start or just get a click. Finally my friend suggested try starting with applied throttle and it barely fired to life. Left the hot fishing grounds to get back before it gets bad. Well Boat struggled most of the way back with fluctuating throttle. Im confused and would appreciate anyone's help and suggestions on what I can do next to rid this damn gremlin
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Old 09-13-2019, 07:04 PM
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It may be time to pull the injectors and send them out to be cleaned professionally. Way better than Seafoam.
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Old 09-13-2019, 07:57 PM
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Originally Posted by SeaCat22 View Post
It may be time to pull the injectors and send them out to be cleaned professionally. Way better than Seafoam.
Yeah, gonna try that but what does a pro do different then pulling each, running pressurized air and cleaner through each? I'll look into it though thanks.
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Old 09-14-2019, 05:58 AM
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If the motor isn’t turning over, you have a bad battery cable or corroded/loose crimp somewhere. I would be checking all battery cable connections very carefully. If they’re more than 10 years old, time to replace with marine grade tinned copper and at least 2 AWG cable size. Be sure to use tinned copper lugs and heat shrink.

Being 95s, those engines have Laser injection which are very sensitive to voltage. You need good power going in at all times. Be sure your batteries have lock nuts on them as well.

Having the injectors cleaned and flowed wouldn’t be a bad idea either way. I think RPM Diesel in Ft. Lauderdale used to charge something like $15 an injector, money well spent for peace of mind and to ensure you don’t lean out a cylinder and blow up the motor.
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Old 09-14-2019, 08:27 AM
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Originally Posted by sundancekid View Post
If the motor isn’t turning over, you have a bad battery cable or corroded/loose crimp somewhere. I would be checking all battery cable connections very carefully. If they’re more than 10 years old, time to replace with marine grade tinned copper and at least 2 AWG cable size. Be sure to use tinned copper lugs and heat shrink.

Being 95s, those engines have Laser injection which are very sensitive to voltage. You need good power going in at all times. Be sure your batteries have lock nuts on them as well.

Having the injectors cleaned and flowed wouldn’t be a bad idea either way. I think RPM Diesel in Ft. Lauderdale used to charge something like $15 an injector, money well spent for peace of mind and to ensure you don’t lean out a cylinder and blow up the motor.
Thanks Kid!! That information is very good to know and will look into that. Typical buying a BOAT. Break Out Another Thousand. Everything I've done to it by myself already is easily over $1k if I was not mechanically inclined and had to take it to a shop. I love this forum!
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Old 09-14-2019, 08:31 AM
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Not sure I would be going 40 miles off-shore and shutting down on a motor with known fuel/start issues... especially with a single. Even with a perfectly running single...
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Old 09-14-2019, 09:46 AM
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Check your fuel pump relay and wiring to it. Its a long shot, but Symptoms fit. If the Fuel injectors were bad you would loose high ind power. This sounds like a engine hot issue. You should also ohm out your ignition wire to the ignition, ecu and fuel pump. I chased an issue for a year and it was one of the connectors. I was only getting 5 volts to my fuel pump relay when it was hot and it wouldn't fire, Cold I had about 8 even with 14.4 which was just enough to close the contacts. Replaced the connection and boom, battery voltage at relay in all conditions.

Long shot but worth looking at.
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Old 09-14-2019, 12:41 PM
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Originally Posted by EMC Pursuit View Post
Check your fuel pump relay and wiring to it. Its a long shot, but Symptoms fit. If the Fuel injectors were bad you would loose high ind power. This sounds like a engine hot issue. You should also ohm out your ignition wire to the ignition, ecu and fuel pump. I chased an issue for a year and it was one of the connectors. I was only getting 5 volts to my fuel pump relay when it was hot and it wouldn't fire, Cold I had about 8 even with 14.4 which was just enough to close the contacts. Replaced the connection and boom, battery voltage at relay in all conditions.

Long shot but worth looking at.
Thanks another good tip! Gonna try this and everything else. I have time as pretty much all the boat shops here in Southern California have a 6 week wait just to bring in the boat.
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