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Question

I HAVE A 1999 MERCURY 150HP EFI AND AS IT GETS COLDER HERE IN WYOMING IT IS STARTING HARD AND SMOKES VERY BADLY. IS IT POSSIBLE THE TEMP SENSOR IS NOT SENDING THE CORRECT SIGNAL TO ECU AS IT DOES NOT PICK UP THE RPM ON ITS OWN. MAYBE IT IS NOT SUPPOSED TO BUT SEEMS TO MAKE SENSE WITH A EFI ENGINE. IF SO WHAT ARE THE TEST PROCEDURES FOR THIS PROBLEM???

Submitted: 21 days and 7 hours ago.
Category: Boat
Value: $28
Status: CLOSED
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Posted by shane j forrest 20 days and 23 hours ago.

Info Request

Do you have access to a mercrury marine scan tool?

20 days and 23 hours ago.

Reply

I OWN ONE OF THE OLDER CARTRIGE OTC TESTERS THAT MERC USED FOR A NUMBER OF YEARS BUT DO NOT HAVE THE CORRECT LINK UP TO THIS ENGINE. HAVE USED IT ON M/C BUT NEVER ON A MERC OB

Posted by shane j forrest 20 days and 23 hours ago.

Answer

Yes that is the one i'm familliar with. Its black and blue and says quicksilver. You will need to make sure you get the correct harness adaptor and outboard cartridge to use it on your engine.It should pull a code if you are having and issue with a temp sensor.

20 days and 23 hours ago.

Reply

AS I WAS A MARINE TECH FOR 15 YEARS YOUR ANSWER IS ONE I ALREADY KNEW. AS I DO NOT HAVE ANY MANUELS AND HAVE NOT WORKED ON BOATS FOR 5 YEARS I WAS HOPING THERE WOULD BE SOME FORM OF OHMS TESTS THAT WOULD HELP ME FIGURE THIS OUT WITH OUT BUYING ANOTHER TOOL THAT I DO NOT USE ON A NORMAL BASIS. THANKS

Posted by shane j forrest 20 days and 11 hours ago.

Answer

I can do some checking for an ohms test .I will need your engine serial number.I have seen this issue on a few of these engines and more times then not the ecu has an internal failure. I will do some checking when you get that serial number to me thank you,shane

20 days and 11 hours ago.

Reply

will get them for you at lunch today

Posted by shane j forrest 20 days and 10 hours ago.

Info Request

Ok sounds good thank you,shane

20 days and 7 hours ago.

Reply

150efi OG926318 1999

Posted by shane j forrest 20 days and 7 hours ago.

Info Request

Ok i will get on this for you.

Accepted Answer

Ok first thing you need to check is that the vst tank is not dumping fuel into the intake manifold threw the vent line.Second the map sensor and the air temp sensor can cause this problem also.The only problem is that you have to watch the ddt to see what the air temp is and what the barometric pressure is.I double checked with a tech at mercury on this with the scan tool and he agreed with me.He also said there is not a spec for ohms on the air temp sensor.Try checking the vst vent line first if that appears to be ok then i would invest in the harness and cartridge for your ddt.

Edited by shane j forrest on 11/2/2009 at 9:06 PM

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Expert: shane j forrest
Pos. Feedback: 100.0 %
Accepts: 
Answered: 11/2/2009

Marine Mechanic

20 years experience merc,volvo,omc

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