2001 merc 200 efi no power, bogs down when hot, runs like new when cold

I have a 2001 merc efi on a ranger bass boat. Runs like new when cold but when u cut it off the recrank it it bogs down and loses all power. I have had this boat to three different mechanics to have it fixed and noone has been able to fix it yet. I have had the whole fuel system gone thru and cleaned up twice. new plugs and fuel filters several times, now i have broke down and bought a new computer $2000 non refundable and that still did not fix it. Last mechanic told me he couldnt figure out what was wrong with it because it ran fine with the cowling off when he hooked his computer up but when he put the cowling back on it wouldnt run so he couldnt diagnose the problem without the cowling off to use his computer and he would have to throw parts at it to fix it. is there anybody out there who has seen this problem before or knows how to fix it. I am now $3600 in the hole on this motor with no results and NEED HELP!!

Re: 2001 merc 200 efi no power, bogs down when hot, runs like new when cold

Has anyone pulled the temp sensors and tested them?

Sometimes people rely on the computer to tell us what is wrong, but a sensor that isn't really out of range, just not reading correctly, can make a great difference.

Pull the temp sensors, Ohm test them, heat them in a pan of water and watch the readings change. Compare your findings with the service manual.

Also check the air passages in the cowling, any restriction may run fine (rich) cold, yet continue to rich (poor) once warmed up.

Re: 2001 merc 200 efi no power, bogs down when hot, runs like new when cold

thanx for your reply!!!! As far as i know noone has checked the temp sensors so thats where ill go next. I just checked the air passages in the cowling and they are clear. Do you think it could be the stator?

Re: 2001 merc 200 efi no power, bogs down when hot, runs like new when cold

If the stator is heating and loosing voltage, since there is NO RETURN on electrical parts PROVE IT, DVA test the stator cold, then again hot, see if there is a noticable difference.

I have seen a number of faulty temp sensors that are within range so as not to throw a trouble code, yet make an engine seriously sick running once to temp. Again, prove it, watch the resistance chang as the sensor is heated, see if it compares to the chart in the service manual.