Sensors for ECM on Mercruiser

[bajadawg]

Hi
Does anyone know it there are two water temp sensors on 350 mag mpi
My guages say 152 deg at normal operating temp!
What temp sensor sends a reading to the ECM?
My engene wont start Hot or Cold until I give full throttle!!
I changed the IAC,MAPT, No code acording th 3 hours Cert Merc mechanic scan!
Thanks
Anyone had any issue like this?

 

[w317chester]

Re: Sensors for ECM on Mercruiser

It depends on the year model of the engine but the water temp sender is probably going to be mounted on the thermostat housing. It will probably just be a single wire snapped onto a terminal (similar to how a spark plug wire snaps onto a spark plug but only smaller). And yes 152*F sounds about right. It probably has a 160*F thermostat in it.

 

[Don S]

Re: Sensors for ECM on Mercruiser

Post your engine Serial number. Year only tells us the boat year, not necessarily the engine year.
You need to understand one other thing, a lot of things can happen to that engine and NOT set a code, including a faulty ECT sensor. It could give a false reading but the ECM doesn't know if it's false or not.
Best thing you could do while posting your engines SN is also tell us exactly what the problem is. There are also a lot of shops that look for codes, if there isn't any, they throw their hands up and have no clue what to do next.

 

[bajadawg]

Re: Sensors for ECM on Mercruiser

Thanks Don
My problemb is the 350 mag mpi is Very Hard to Start whether my engine is Cold or Normal op. temp.
This started about a year ago about the time I switched from main fuel tank to aux. fuel tank when the main ran dry on a 200 mile trip.
My 2005 Mercruise ser. number is OW332421 4442087TT
I have spent a fortune on parts that the mechanic says it could be, first replaced IAC $140 then MAP $240 then TEMP $120 sensors With $400 labor Scaning.
Now I see someone posted the ECM could be the problemb but I need to buy a $1200 item with no return policy & may not be the problemb.
I know someone sead get a good mechanic!! I have had 3 so far, and each is as dumb as the other with all there Merc. placks hanging on there walls

 

[fossill]

Re: Sensors for ECM on Mercruiser

You're probably just as far ahead getting the tools and manual and troubleshoot it yourself. Sounds like all they did was throw parts at it hoping to fix it.
Before you get into troubleshooting the electronics end of things, start with checking out the the basics first and make sure thats all in order. then worry about codes.