Help Please, before it goes to dealer service !!!!!

[magnoman]

My 98 225 EFI is running rough the whole boat shakes at 900-1300 rpm. There is no problem starting, running at cruising speed.This all seemed to start happening when I took off the O2 sensor to check the condition of the o2 rod that goes into the cyl head. I know they are prone to getting clogged and I check mine a few times a season. after that it started to run rough? I checked the O2 sensor and the wires seemed to be pinched and it was origanal 98 so I bought a new one $250! and it still runs rough at low rpm?
any ideas anyone? I did put in the fuel additive for the ethanol problems that so many people seem to be having but I have a plastic gas tank in my boat and never had any troubles with fuel...

 

[MikDee]

Re: Help Please, before it goes to dealer service !!!!!

Was there a reason you replaced the O2 sensor? Was this problem there beforehand? It may be something else that is the cause, Anyway, apparently, there may be a trouble code set on your ECM (engine computer module) that needs to be cleared, try removing your battery cables for about 15mins, to see if it automatically resets. If this don't work, you'll have to go through the service manual.

 

[magnoman]

Re: Help Please, before it goes to dealer service !!!!!

I took off the old O2 sensor to clean it and ever since then it has ran rough at low rpm.. I noticed that the wires going to the O2 looked to be pinched from removing it all those times , so I bought a new one?
I will try resetting the ECU with the batt cables thanx so much.

 

[rodbolt]

Re: Help Please, before it goes to dealer service !!!!!

there is no reset on the ECU. if the code is active its stored, if its not its cleared.
test the O2 sensor output voltage, it should vary between about .35V and.6V.
with the gearcase fully submerged and the engine at operating tempreture.
check that the heads are at about 125*.
you may also wish to check for fuel leakage from a pump diaphram.

 

[magnoman]

Re: Help Please, before it goes to dealer service !!!!!

Thanks for the advice! It just seems strange that it started happing after I took the orig O2 off to check and clean the plunger? ever since I put it back low rpm is shake rattle and roll....
How do i go about checking the fuel diaphragm?