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Outboard motor help

Posted on 1/17/25 at 7:42 am
Posted by LINOESC
Member since Jan 2025
472 posts
Posted on 1/17/25 at 7:42 am
Any experts on here with advice ?
I have a Mercury pro xs 250. Was out fishing yesterday, while trolling the motor killed. Tried to restart and motor would turn over but not start. Checked kill switch position, it was ok. Seems no fire to the motor?
This post was edited on 1/17/25 at 7:57 am
Posted by Major Dutch Schaefer
Location: Classified
Member since Nov 2011
35769 posts
Posted on 1/17/25 at 8:45 am to
Is it getting fuel?
Posted by TFLEX
TX
Member since Jun 2023
192 posts
Posted on 1/17/25 at 9:15 am to
Well- if it turns over- you need 3 things to start - air, fuel, spark.

Buy a cheap spark tester and verify all plugs are sparking, if that's good then verify fuel pump is sending fuel etc.

If those don't fix it then you need to compression test and depending if that's good start looking for electronic gremlins.

Good luck
Posted by SCwTiger
armpit of 'merica
Member since Aug 2014
6628 posts
Posted on 1/17/25 at 11:16 am to
I had this problem last summer after I changed my cranking battery. Turned out I needed a new ECM (brain that delivers fire). $3k later it was all good.

I hope that’s not your problem.
Posted by DownshiftAndFloorIt
Here
Member since Jan 2011
69412 posts
Posted on 1/17/25 at 11:21 am to
Optimax have an ecm and datalink capability, so it's worth having a way to read fault codes if you're going to attempt to fix it yourself.

There's no telling wtf is wrong with it based on this information. Could be fuel, could be the ecm, could be the keyswitch. Could be literally anything.
Posted by Basura Blanco
Member since Dec 2011
10832 posts
Posted on 1/17/25 at 3:04 pm to
quote:

Tried to restart and motor would turn over but not start. Checked kill switch position, it was ok. Seems no fire to the motor?


If the motor turned over, its not the kill switch, nor is it likely at the key switch itself. If it quit while trolling, my first guess would be fuel as opposed to spark. Either on the supply side with bad gas (unlikely if it were running fine up until it quit), clogged pickup in the tank, or a supply line filter/water separator clogged. Is there pressure on the bulb of the fuel line? If not, does it get tight if you pump it? Unlikely a vapor lock while running but it happens.

If its on the motor side it could be a clogged fuel filter. I would eliminate those possible issues before jumping to digital/sensor issues.

This all from someone who missed a flat morning of fishing earlier and fought a fuel issue for a few hours before realizing he had installed a new fuel line from the tank to the motor backwards. Which meant every time I pumped the bulb to get fuel to the motor I was sucking it from the motor. Which would explain why it ran fine for 4-5 minutes on the gas trapped in the motor and quit once that was exhausted and wouldn't start back up. You would think the gurgling in the tank as I pumped the bulb a few hundred thousand times would've been a dead give away to my dumbass. Nope.

Posted by Cracker
in a box
Member since Nov 2009
18927 posts
Posted on 1/17/25 at 6:45 pm to
wrong
not be a dick, but proper timing matters but you are correct
Posted by DTRooster
Belle River, La
Member since Dec 2013
8641 posts
Posted on 1/17/25 at 8:08 pm to
quote:

Could be literally anything
the starter is probably ok
This post was edited on 1/17/25 at 8:10 pm
Posted by Nascar Fan
Columbia La.
Member since Jul 2011
18582 posts
Posted on 1/17/25 at 8:12 pm to
Fuse
Posted by John_V
SELA
Member since Oct 2018
1995 posts
Posted on 1/18/25 at 12:04 am to
Did you try to start it again later in the day? My old one was having identical issues at times due to being "flooded" for something being a tad bit off on the fuel end.

One time I tried using my trolling motor to get like 6 miles back to the ramp when the outboard crapped out thinking it was done for. Ended up starting about an hour later when I the fuel supply got right.
Posted by Stat M Repairman
Member since Jun 2023
336 posts
Posted on 1/18/25 at 11:28 am to
Yeah man could be anything based on what you said.

If you got a primer bulb you might look at that. Theres a check valve in there thats not supposed to let fuel flow back in the system. If it's bad it can let air in or fuel out.

Also I'd look at fuel quality. Have seen where a blob of ethanol that been floating around in the take gets in the fuel pickup and clogs up your fuel system. You might be good on a full tank but as you burn fuel the probably of bad gas getting sucked in from the bottom of the tanks goes up. This tends to happen in bad weather and the worst possible time.
This post was edited on 1/18/25 at 11:29 am
Posted by LINOESC
Member since Jan 2025
472 posts
Posted on 1/18/25 at 12:32 pm to
Yeah I tried it. It turns over fine ,but doesn’t seem to be getting any spark. Gonna bring it in next week and have it looked at
Posted by tes fou
Member since Feb 2014
923 posts
Posted on 1/18/25 at 7:52 pm to
There are several common outboard problems like the demand valve, primer bulb or fuel pickup that can cause you to lose fuel supply. Those are usually easier to diagnose than engine problems.

Optimax has a compressor and a couple little diaphragms etc that can be finicky. Without the ability to check fuel/air pressures etc they can be tough to diagnose.

Lot of guys waste a lot of time and cash throwing random parts at outboards that they don’t have the proper resources to diagnose.
Posted by boomerhuntsducks
Pass LaLoutre, Louisiana
Member since Jan 2016
11 posts
Posted on 1/19/25 at 7:18 am to
Start simple, charge your starting battery. Cold weather equals poor battery performance. if you don’t have enough voltage, even though it cranks, the ecm will not work. From another…. Preferably, the voltage should remain at a minimum of 11.5VDC even while cranking/trimming.

Somewhere around 11.1 VDC, weird things.
Posted by LanierSpots
Sarasota, Florida
Member since Sep 2010
66809 posts
Posted on 1/19/25 at 8:11 am to
quote:

Fuse



My ProXS's always blew fuses and coils. If the coil opened up, it would not blow the fuse but if it shorted, it would.


Posted by Lsutigerturner
Member since Dec 2016
6844 posts
Posted on 1/19/25 at 8:43 am to
It’s not kill switch if it continues to try and turn over.

Could be anything but my experience with alll my motor issues is that it’s fuel. It’s always fuel for me lol

Check for blocks in fuel system, you can do it first or last but pull fuel line from one of your fuel rails and see if when you prime the engine before starting if the fuel pumps turn on. If you NOT getting fuel then, check primer bulb make sure it’s hard and working, then check fuel water separator, then check the vst and crack it open see what debris you have in the internal thimble style filter, then check high pressure fuel filter
This post was edited on 1/19/25 at 10:45 am
Posted by AlxTgr
Kyre Banorg
Member since Oct 2003
84684 posts
Posted on 1/19/25 at 9:10 am to
Two posters are saying if it turns over, it's not the kill switch. Every 2 stroke Merc I have ever had(6) would crank with the kill pulled. It just would not start.
Posted by DTRooster
Belle River, La
Member since Dec 2013
8641 posts
Posted on 1/20/25 at 1:30 am to
That’s correct.
Posted by Basura Blanco
Member since Dec 2011
10832 posts
Posted on 1/20/25 at 3:58 pm to
quote:

Every 2 stroke Merc I have ever had(6) would crank with the kill pulled. It just would not start.


Thats a new one on me. I have never owned a 2 stroke Merc and obviously never owned a motor that did that.
Posted by AlxTgr
Kyre Banorg
Member since Oct 2003
84684 posts
Posted on 1/20/25 at 7:22 pm to
Until you guys posted, I had never heard of the kill switch preventing the motor from turning over.
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