Omc 5.8 under temp?

[JON NEELEY]

I Have a omc 5.8 EFI 351 that runs at 120 degrees at idle and on the water. The rps at idle are 500 and should be 600 according to tag on motor. My question is, if the motor is running to cool will the engine not reach optimum operating temp and the ecm send mixed signals? At idle the engine revs from 500 to 600 back and forth..Any input would be great!!!!!!!!

 

[Levinz11]

Re: Omc 5.8 under temp?

I don't know about your boat engine but...when a thermostat gets stuck open and doesn't allow a car engine to come up to normal operating temp. the computer injects extra gas. Some call this an "open loop" condition. Doesn't hurt anything but your MPG's and maybe your catalytic converter.

To answer your question: a too cool engine will normally idle higher due to the ECM injecting the extra gas.

I would try to verify the temp gauge and thermostat are working correctly. That engine may have 2 temp sensors/senders...one for the ECM and one for the gauge. Get our your multimeter and your manual and start checking if these are working correctly.

Good Luck.

 

[JON NEELEY]

Re: Omc 5.8 under temp?

THANKS LEVINZ11, I was hopig for some general input and all theories are appreciated!!!!!!!

 

[JON NEELEY]

Re: Omc 5.8 under temp?

I have gone over and over the manual and feel that I can perform any and every electrical test in there, however I must be missing some of the manual because the most basic things like timing specs, plug gap,operating temp etc I cant seem to find. Is there a seperate manual other than shop manual I have?

 

[Don S]

Re: Omc 5.8 under temp?

What's the full model number of your engine?

Is there a seperate manual other than shop manual I have?

Don't know what manual you have, so can't say.

 

[JON NEELEY]

Re: Omc 5.8 under temp?

What's the full model number of your engine?



Don't know what manual you have, so can't say.

Hi Don,
96 omc 5.8
58fcpnca is model #
T01291118 is ser #
thx for any help

 

[Don S]

Re: Omc 5.8 under temp?

I would replace the thermostat. You should have a 160? stat in it. When running 120, the ecm will run richer and may not idle very well.
If you have the OEM service manual set, you should find the information in the Electrical and Ignition manual from the set.

If it's been running cold for a long time, I would imagine the plugs could be fouled. The tuneup may help, but you really have to get the temp up where it should be.

 

[JON NEELEY]

Re: Omc 5.8 under temp?

ok thx Don, Common sense told me that 120 was to cold. It idles with a surge from 500 to 600 or so and back and forth. I did just change the plugs 3 days ago and swear they were the original plugs. I bought this boat in the spring. I knew 500 idle rpm was a bit low and should be 600. I will replace thermostat and see what happens. I will post back after my findings.

 

[JON NEELEY]

Re: Omc 5.8 under temp?

Don, I list my engine # in previous post. I looked up thermostat in the parts on here in the omc section but dont seem to find mine. can you or someone please just tell me the omc part # so I can order tomorrow. thank you!!!!!

 

[Don S]

Re: Omc 5.8 under temp?

Here is the BRP site for parts lookup. Might want to bookmark it.

http://epc.brp.com/SiteMods/BRP_Pub...efault.aspx?brands=ej&lang=E&brands=ej&lang=E

Once you get there, using your model number, you will need items 3,4,and 5.

 

[JON NEELEY]

Re: Omc 5.8 under temp?


I went to do some testing with my home made test kit:facepalm: and my test plug is not the same. Unsure which wires to probe lites and clip to?
96 omc 5.8L
58fcpnca

MOVED TO NEW THREAD!!!