Hi, I have a 1997 V6 175hp EFI mercury and its broken down the last 3 out of 4 outings. I've taken it to a Marine mechanic the first time it broke down, he ran a few checks including fuel pressure test and tested it for ethanol and all came up okay.
Boat will start at home, start at the ramp, start in the water and run okay until you reach your 1st destination which can be anywhere from 5 min run from the ramp to 1 hour run. Once you try and start it after you have stop, it will crank but wont fire up. It doesn't overheat at any stage, you can drive for hours around on the first intial fire up, its just starting it up after that. Last time out I removed all the spark plugs and they were fueled up. Anyone had a similar problem or have any idea's?? Could it be possibly a sensor ECT, IAT, Crank angle sensor etc ??
I have tried searching this forum for a repair manual but cant seem to find one!!! Any info would be greatly appreciated.
Regards Charlie...

Need to test fuel pressure and spark check at time it fials to start to find whats going on.
The service manual is listed under Support and Service Material(there wasn't a 175 EFI model listed on 1997 parts listing), Mercury Outboard Parts 1996 1175413SD SERVICE AND SUPPORT MATERIAL Diagram

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sounds very similar to mine. Do you have alot of fuel coming out the exhaust? And do you end up getting it running a second time? if so how. I couldnt get mine to start see my post. "Starting problem, need help"

if you need a service manual email me

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Cheers

Did check the fuel pressure, its running 38psi. Haven't checked for spark, as everytime I have gone to start it since it broke down guess what "It starts". I'm just going to have to run it in a drum of water until it plays up again. Neighbours wont be impressed with the noise

Hi bassbasset, yes I do have a noticable amount of black smoke when cranking, and spark plugs where wet with fuel once I removed them.
The times I have broken down its always been after that first intial run out from the boat ramp. On the next turn of key you can sit there all day cranking and it wont fire up, Not that thats a bad thing my fishing lines are in the water. I also run a twin battery set up so there is plenty of electrical juice to crank it.


It is definantly an electrical / spark problem, possibly a coolant temp senor out of range??
What i'm curious about is, if the temperature warning buzzer would go off if the sensor reading went out of wack the other way as in not hot but to cold reading.

Example: A friend of mine had problems with his car stalling whilst driving or woudn't start once he had driven say more than 10 miles after switching it off. Black smoke would bellow out whilst he tried to start it. He had taken to many car dealers as the vehicle was still under warranty but failed to find the problem, but they all had the same conclusion and said it was a spark problem.
He went to a local workshop the mechanic hooked up the laptop and took it for a run. Bingo the car stalled whilst driving, instantly the coolant temp sensor code started flashing and it read -52 degrees. He replaced the coolant temp sensor and has never had a problem like that ever since.

So thats what I'm asking, would the warning buzzer go off if the coolant temp sensor was faulty and went out of its - minus operating temperature range.

u may have some leaky fuel injectors. hard to say w/o seeing the motor. have you tried some fuel injector cleanser?? has the boat been sitting for a while?? when did the problem develop?

Have you looked at your mechanical (diaphragm) fuel pump?
If you squeeze your primer bulb with the motor idling does it have any effect in the motors behavior?
Is there a slick in the water?
It could be electrical but I doubt it is the IAT or ECT. That motor isn't that sophisticated.
If the IAT or coolant temp sensors were out of whack or even unplugged it would run rich but wouldn't create a no start situation.
I am assuming that you advanced the throttle when it wouldn't start?
If it isn't a fuel pump failure (causing fuel to enter the crankcase) I would be looking at a keyswitch, a kill switch or an ignition component.
How did you get in when it wouldn't start, a tow or did it eventually start?