1993 mercury efi 175 bogs down

[jay576]

Hello all yes just bought this 93astro with a mercury 175efi my son and I were cruising at wide open throttle with no problems at all and had been running the boat awhile when all of a sudden it was as if someone flicked a switch and went from cruising wideopen to about 15 miles an hour and that's with the throttle wide open you can tell for sure that its bogged down made sure butterflies were opening all the ways and they were if this sounds familiar to anyone any help would be appreciated also I checked the spark plugs they are ngk but they have no ground electrode is that plug normal for 93 mercury 175 efi thanks for any help......

 

[CharlieB]

Re: 1993 mercury efi 175 bogs down

The surface gap plugs are correct.

First thing to check is get your hands on an adjustable gap spark tester, set the gap to 7/16 inch and test each plug wire one at a time. You need a strong blue arc, any less and the motor will not perform.

Next you will need a DVA tester or a DVA adaptor for any volt/ohm meter to test the high and low speed output of the stator to each switchbox. A poor high speed output to one switchbox will kill spark to three cyls at high speed and instantly drop RPM to 2500 or less.

You can download the complete Ignition Troubleshooting Guide from the Support pages of CDIElectronics.com

Do NOT assume any parts is bad and replace it without PROVING it bad as there is NO RETURN on electrical parts.

 

[Coloradolakeboy]

Re: 1993 mercury efi 175 bogs down

My Merc Tech service manual specs the NGK's without the electrode so you are good there. I would start with some simple stuff first. Replace fuel and water separating filters and tighten fuel connections. Have you replaced the fuel lines recently? Ethanol in the gas is damaging old fuel lines.
Pull the pick-up tube out of your tank and check it. I would not run it hard until you eliminate fuel supply problems. Charlie B is spot on, my 175 did the same thing and it did need some ignition repairs as well as fuel supply.