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View Full Version : 454 mag mpi problem, advice needed!


JamieP
08-29-2009, 05:31 PM
Hi guys, any help appreciated.

My temp gauge is swinging up and down like a loon and causing my boat the run bad, i presume the ecu is thinking its in cold start and chucking loads of fuel in? any ideas on whats causing this to happen?

Regards Jamie.
Jamesbon
08-29-2009, 07:08 PM
3 things;

Is the temp. gauge accurate?

Check the thermostat..maybe it's defective...

If possible have a "Merc. Man" plug into the engines computer...
gold-n-rod
08-29-2009, 08:33 PM
Bad theromostat. The ECM keeps you in open loop. Fix it, 'cause it's washing your cylinders with an over rich mixture.
JamieP
08-30-2009, 02:50 AM
3 things;

Is the temp. gauge accurate?

Check the thermostat..maybe it's defective...

If possible have a "Merc. Man" plug into the engines computer...


The temp gauge is correct, my man plugged his computer in, no fault codes and its reading the same as the gauge.

He changed the thermostat and its still the same
mrfixxall
08-30-2009, 12:49 PM
The temp gauge is correct, my man plugged his computer in, no fault codes and its reading the same as the gauge.

He changed the thermostat and its still the same


make sure the impeller is good,,may not be getting a consistant flow of water..
JamieP
08-31-2009, 03:59 AM
make sure the impeller is good,,may not be getting a consistant flow of water..


That sounds logical, thanks ill check that out.